U.S. patent application number 15/432380 was filed with the patent office on 2017-06-01 for compositions and methods for hydrocarbon functionalization.
The applicant listed for this patent is The Trustees of Princeton University, The University of Virginia Patent Foundation. Invention is credited to Nicholas C. Boaz, George Fortman, John T. Groves, Thomas Brent Gunnoe.
Application Number | 20170152207 15/432380 |
Document ID | / |
Family ID | 52142671 |
Filed Date | 2017-06-01 |
United States Patent
Application |
20170152207 |
Kind Code |
A1 |
Gunnoe; Thomas Brent ; et
al. |
June 1, 2017 |
COMPOSITIONS AND METHODS FOR HYDROCARBON FUNCTIONALIZATION
Abstract
Embodiments of the present disclosure provide for methods of
hydrocarbon functionalization, methods and systems for converting a
hydrocarbon into a compound including at least one group ((e.g.,
hydroxyl group) (e.g., methane to methanol)), functionalized
hydrocarbons, and the like.
Inventors: |
Gunnoe; Thomas Brent;
(Palmyra, VA) ; Fortman; George; (Phoenixville,
PA) ; Boaz; Nicholas C.; (Ewing, NJ) ; Groves;
John T.; (Princeton, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The University of Virginia Patent Foundation
The Trustees of Princeton University |
Charlottesville
Princeton |
VA
NJ |
US
US |
|
|
Family ID: |
52142671 |
Appl. No.: |
15/432380 |
Filed: |
February 14, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14900621 |
Dec 22, 2015 |
9604890 |
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PCT/US2014/044272 |
Jun 26, 2014 |
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15432380 |
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61839415 |
Jun 26, 2013 |
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61993713 |
May 15, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01J 19/24 20130101;
C07C 19/00 20130101; C07C 67/035 20130101; B01J 2219/24 20130101;
C07C 17/00 20130101; C07C 29/03 20130101; C07C 67/035 20130101;
C10L 1/02 20130101; C07C 67/035 20130101; C07C 29/147 20130101;
C07C 19/043 20130101; C07C 29/00 20130101; C07C 19/03 20130101;
C07C 2602/42 20170501; C07C 69/63 20130101; B01J 2219/00051
20130101; C07C 2603/74 20170501; C07C 69/14 20130101 |
International
Class: |
C07C 67/035 20060101
C07C067/035; C07C 19/03 20060101 C07C019/03; C07C 19/043 20060101
C07C019/043; B01J 19/24 20060101 B01J019/24 |
Goverment Interests
FEDERAL SPONSORSHIP
[0002] This invention was made with government support under Grant
No. DE-SC0001298, awarded by The United States Department of
Energy. The government has certain rights in the invention.
Claims
1. A method, comprising: mixing A.sub.aX.sub.n, an iodine-based
compound, and a source of functionalization to form a first
mixture, wherein A is selected from the group consisting of:
hydrogen, lithium, sodium, potassium, beryllium, magnesium,
calcium, strontium, barium, transition metals, aluminum, gallium,
thallium, indium, tin, sulfur, ammonium (NH.sub.4.sup.+),
alkylammonium. phosphonium (PH.sub.4.sup.+), alkylphosphonium,
arylphosphonium, or trimethyl sulfonium ([S(CH.sub.3).sub.3].sup.+)
and a combination thereof, wherein X is chlorine or bromine,
wherein subscript "a" is an oxidation state of X and subscript "n"
is an oxidation state of A; and mixing the first mixture with a
hydrocarbon in the gas phase; and pressurizing and heating the
mixture with a computer system to make a functionalized
hydrocarbon.
2. The method of claim 1, further comprising: converting the
functionalized hydrocarbon to a compound including at least one
group selected from the group consisting of: hydroxyl, halide,
carbonyl, and a combination thereof.
3. The method of claim 2, wherein the compound is selected from an
alcohol or glycol.
4. The method of claim 2, wherein the compound is methanol,
ethanol, or propanol.
5. The method of claim 1, wherein the hydrocarbon is selected from
the group consisting of: methane, ethane, propane, butane, and a
combination thereof.
6. The method of claim 1, wherein the hydrocarbon is aliphatic.
7. The method of claim 1, wherein the hydrocarbon is aromatic.
8. The method of claim 1, wherein A.sub.aX.sub.n is selected from
the group consisting of: HCl, NaCl, KCl, CaCl.sub.2, LiCl,
ZnCl.sub.2, BeCl.sub.2, MgCl.sub.2, PCl.sub.3, NH.sub.4Cl,
CCl.sub.4, CHCl.sub.3, transition metal chlorides, main group metal
chlorides or organochlorides, or combination thereof.
9. The method of claim 1, wherein the iodine-based compound is
selected from the group consisting of: iodate, periodate, iodine
oxide, iodosyl (IO.sup.+), trivalent iodine compound, and a
combination thereof.
10. The method of claim 1, wherein the iodine-based compound is
Q(IO.sub.3).sub.p, wherein Q is selected from the group consisting
of: hydrogen, lithium, sodium, potassium, beryllium, magnesium,
calcium, strontium, barium, transition metals, aluminum, gallium,
thallium, indium, tin, sulfur, ammonium (NH.sub.4.sup.+),
alkylammonium. phosphonium (PH.sub.4.sup.+), alkylphosphonium,
arylphosphonium, and trimethyl sulfonium
([S(CH.sub.3).sub.3].sup.+), wherein "p" is 1 to 5.
11. The method of claim 1, wherein the iodine-based compound is
selected from the group consisting of: KIO.sub.3,
Ca(IO.sub.3).sub.2, Ba(IO.sub.3).sub.2, Cu(IO.sub.3).sub.2,
NH.sub.4IO.sub.3, H.sub.5IO.sub.6, KIO.sub.4, NaIO.sub.4 and
NH.sub.4IO.sub.4, I(TFA).sub.3, I.sub.2O.sub.5, [IO].sup.+,
[IO.sub.2].sup.+, and combination thereof.
12. The method of claim 1, wherein the source of functionalization
is selected from the group consisting of: trifluoroacetic acid,
trifluoroacetic anhydride, hexafluorobutyric acid, water, sulfuric
acid, acetic acid, supercritical carbon dioxide, phosphoric acids,
and a combination thereof.
13. The method of claim 1, wherein mixing the first mixture with
the hydrocarbon is conducted at an internal pressure of about 15 to
1500 psi and at a temperature of about 25 to 300.degree. C. for
about 10 minutes to 5 days.
14. The method of claim 1, wherein A.sub.aX.sub.n is about 0.2 to
25 weight % of the first mixture, wherein the iodine-based compound
is about 2 to 40 weight % of the first mixture, wherein the source
of functionalization is about 30 to 95 weight % of the first
mixture, and wherein the amount of the hydrocarbon relative to the
first mixture is about 0.01 to 20 weight %.
15. The method of claim 1, wherein the mass of A.sub.aX.sub.n
relative to the source of functionalization is about 0.14 to 10%
and wherein the mass of the iodine-based compound relative to the
source of functionalization is about 17 to 26%.
16. A system for producing a functionalized hydrocarbon,
comprising: a vessel including A.sub.aX.sub.n, an iodine-based
compound, and a source of functionalization to form a first mixture
and a hydrocarbon, wherein A is selected from the group consisting
of: hydrogen, lithium, sodium, potassium, beryllium, magnesium,
calcium, strontium, barium, transition metals, aluminum, gallium,
thallium, indium, tin, sulfur, ammonium (NH.sub.4.sup.+),
alkylammonium. phosphonium (PH.sub.4.sup.+), alkylphosphonium,
arylphosphonium, or trimethyl sulfonium ([S(CH.sub.3).sub.3].sup.+)
and a combination thereof, wherein X is chlorine or bromine,
wherein "a" is the oxidation state of X and "n" is the oxidation
state of A; wherein the vessel includes a pressure system to
pressurize the vessel to about 15 to 1500 psi and a heating system
to heat the vessel to about 25 to 300.degree. C.; and wherein the
vessel includes a system to mix the contents of the vessel.
17. The method of claim 1, wherein A is selected from the group
consisting of: hydrogen, lithium, sodium, potassium, beryllium,
magnesium, calcium, strontium, barium, aluminum, gallium, thallium,
indium, tin, sulfur, ammonium (NH.sub.4.sup.+), alkylammonium.
phosphonium (PH.sub.4.sup.+), alkylphosphonium, arylphosphonium, or
trimethyl sulfonium ([S(CH.sub.3).sub.3].sup.+) and a combination
thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of, and claims priority
to, co-pending U.S. application entitled "COMPOSITIONS AND METHODS
FOR HYDROCARBON FUNCTIONALIZATION," having Ser. No. 14/900,621 and
filed in the United States on Dec. 22, 2015, which is entirely
incorporated herein by reference. U.S. Patent application, having
Ser. No. 14/900,621, is the 35 U.S.C. .sctn.371 national stage
application of PCT Application No. PCT/US2014/044272, filed Jun.
26, 2014, which is entirely incorporated herein by reference.
PCT/US2014/044272 claims priority to U.S. provisional application
entitled "COMPOSITIONS AND METHODS FOR HYDROCARBON
FUNCTIONALIZATION," having Ser. No. 61/839,415, filed on Jun. 26,
2013, which is entirely incorporated herein by reference.
PCT/US2014/044272 also claims priority to U.S. provisional
application entitled "COMPOSITIONS AND METHODS FOR HYDROCARBON
FUNCTIONALIZATION," having Ser. No. 61/993,713, filed on May 15,
2014, which is entirely incorporated herein by reference.
BACKGROUND
[0003] Hydrocarbons, molecules composed entirely of carbon and
hydrogen, are the predominant components of fossil resources
including coal, petroleum, and natural gas. The conversion of raw
hydrocarbons derived from fossil resources is fundamental to the
energy sector as well as the petrochemical sector. One of the more
challenging classes of hydrocarbons to convert to higher value
compounds and fuels is derived from natural gas, which is composed
predominately of alkanes, mostly methane (CH.sub.4) but also ethane
(C.sub.2H.sub.6), propane (C.sub.3H.sub.8), and butane
(C.sub.4H.sub.10). Current methods to convert the alkanes from
natural gas into higher value compounds (including olefins and
liquid fuel such as methanol) involve processes that are energy
intensive. For example, the conversion of methane to methanol (a
liquid fuel and useful chemical precursor) provides a viable route
to transition natural gas into liquid fuel and high value
chemicals, but the transformation of methane into methanol by
current technologies requires methane reforming to generate carbon
monoxide and dihydrogen (known as "synthesis" or syn gas) followed
by Fischer-Tropsch catalysis. For the formation of olefins, high
temperature "cracking" is required. These processes require high
temperature and pressure, and the infrastructure (including the
chemical plants and infrastructure to deliver natural gas) for them
is very expensive.
[0004] Despite the recent increase in natural gas availability and
reduction in expense, scaled use of natural gas as a fuel for the
transportation sector or a feedstock for the petrochemical industry
has been limited by the expense of the infrastructure for the
processing plants and for movement of natural gas. Thus, there is a
need to overcome these challenges.
SUMMARY
[0005] Embodiments of the present disclosure provide for methods of
hydrocarbon functionalization, methods and systems for converting a
hydrocarbon into a compound including at least one group (e.g.,
hydroxyl group) (e.g., methane to methanol), functionalized
hydrocarbons, and the like.
[0006] An exemplary embodiment of the method includes, among
others, includes: mixing A.sub.aX.sub.n, an iodine-based compound,
and a source of functionalization to form a first mixture, wherein
A is selected from the group consisting of: hydrogen, lithium,
sodium, potassium, beryllium, magnesium, calcium, strontium,
barium, transition metals, aluminum, gallium, thallium, indium,
tin, sulfur, ammonium (NH.sub.4.sup.+), alkylammonium, phosphonium
(PH.sub.4.sup.+), alkylphosphonium, arylphosphonium, or trimethyl
sulfonium ([S(CH.sub.3).sub.3].sup.+) and a combination thereof,
wherein X is a halide (e.g., chlorine), wherein subscript "a" is
the oxidation state of X and subscript "n" is the oxidation state
of A; and mixing the first mixture with a hydrocarbon in the gas
phase to make a functionalized hydrocarbon. In an embodiment, the
method can include converting the functionalized hydrocarbon to a
compound including at least one group selected from the group
consisting of: hydroxyl, halide, carbonyl, ester and a combination
thereof.
[0007] An exemplary embodiment of the system for producing a
functionalized hydrocarbon includes, among others, includes: a
vessel including A.sub.aX.sub.n, an iodine-based compound, and a
source of functionalization to form a first mixture and a
hydrocarbon, wherein A is selected from the group consisting of:
hydrogen, lithium, sodium, potassium, beryllium, magnesium,
calcium, strontium, barium, transition metals, aluminum, gallium,
thallium, indium, tin, sulfur, ammonium (NH.sub.4.sup.+),
alkylammonium, phosphonium (PH.sub.4.sup.+), alkylphosphonium,
arylphosphonium, or trimethyl sulfonium ([S(CH.sub.3).sub.3].sup.+)
and a combination thereof, wherein X is a halide (e.g., chlorine),
wherein "a" is the oxidation state of X and "n" is the oxidation
state of A; wherein the vessel includes a pressure system to
pressurize the vessel to about 15 to 1500 psi and a heating system
to heat the vessel to about 25 to 300.degree. C.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Further aspects of the present disclosure will be more
readily appreciated upon review of the detailed description of its
various embodiments, described below, when taken in conjunction
with the accompanying drawings.
[0009] FIG. 1.1 illustrates a .sup.1H NMR spectrum
(HTFA--C.sub.6D.sub.6 insert; 600 MHz) from the reaction in example
1 with a cyclopentane standard added and C.sub.6D.sub.6 insert.
11.07 ppm--trifluoroacetic acid, 7.16 ppm--benzene-d.sub.6 insert,
4.40 ppm--methyl trifluoroacetic ester, 1.87 ppm--cyclopentane
standard.
[0010] FIG. 1.2 illustrates a .sup.13C NMR spectrum
(HTFA--C.sub.6D.sub.6 insert; 200 MHz) from the reaction of example
1 with a cyclopentane standard added. MeTFA .delta. (ppm): 160.9
(q, .sup.2J.sub.CF=43 Hz, C.dbd.O), 115.0 (overlap with HTFA, q,
.sup.1J.sub.CF=283 Hz, CF.sub.3), 54.8 (q, .sup.3J.sub.CF=8.9 Hz,
CH.sub.3).
[0011] FIG. 1.3 illustrates a GC-MS plot of a reaction from example
1: (A) Mass count response. Elution time of MeTFA=5.43. (B) Mass
spectrum (with subtracted background) at t=5.43. (C) Mass spectrum
of methyl trifluoromethylacetate ester from 2008 NIST library.
[0012] FIG. 2.1 illustrates .sup.1H NMR spectra resulting from the
partial oxidation of methane when .sup.13C-MeTFA was added to the
initial reaction mixture (bottom spectrum B). At least 85% of
.sup.13C-MeTFA was retained over 1 h (top spectrum A). Conditions:
0.90 mmol .sup.13C-MeTFA; 0.676 mmol KCl; 7.7 mmol
NH.sub.4IO.sub.3; 8.0 mL HTFA; p.sub.CH4/Ne=3450 kPa (8.4 mmol
CH.sub.4); 800 rpm; 180.degree. C.; 1 h.
[0013] FIG. 2.2 illustrates .sup.1H NMR and .sup.13C NMR spectra of
a reaction mixture starting with .sup.13CH.sub.4. Conditions: 0.17
mM KCl; 1.13 mM KIO.sub.3; 2.0 mL HTFA; p.sub.CH4=240 kPa; total
pressure filled to 5520 kPa with Ar; 180.degree. C.; 2 h; 600
rpm.
[0014] FIG. 2.3 illustrates the production of MeTFA as a function
of initial methane pressure. Conditions: 0.338 mmol KCl; 2.26 mmol
KIO.sub.3; 2.0 mL HTFA; 180.degree. C.; 2 h; 600 rpm.
[0015] FIG. 2.4 illustrates MeTFA production as a function of
temperature. Conditions: 0.676 mmol KCl; 7.7 mmol NH.sub.4IO.sub.3;
8.0 mL HTFA; p.sub.CH4/Ne=3450 kPa (8.4 mmol CH.sub.4); 800 rpm; 20
min.
[0016] FIG. 2.5 illustrates a comparison of halides, chloride
sources and iodate sources for the partial oxidation of methane.
Conditions: 0.338 mmol X.sup.-; 2.26 mmol IO.sub.3.sup.-; 2.0 mL
HTFA; p.sub.CH4/Ne=5520 kPa; 180.degree. C.; 2 h; 600 rpm.
NH.sub.4IO.sub.3 was used as the oxidant for the reactions
involving M.sup.n+Cl.sub.n and KX. KCl was used in the reactions
involving M.sup.n+(IO.sub.3).sub.n.
[0017] FIG. 2.6 illustrates a .sup.1H NMR spectrum from reaction of
C.sub.2H.sub.6 with HTFA in the presence of NH.sub.4IO.sub.3 and
KCl. Conditions: 0.676 mmol KCl; 7.7 mmol NH.sub.4IO.sub.3; 8.0 mL
HTFA; p.sub.C2H6=2070 kPa; 180.degree. C.; 1 h; 800 rpm.
[0018] FIG. 3.1 illustrates a .sup.1H NMR spectrum of a reaction
mixture, measured in trifluoroacetic acid with capillary containing
benzene-D.sub.6. 5.2 ppm: dichloromethane, 4.8 ppm:
methyltrifluoroacetate.
[0019] FIG. 4.1 is a scheme that illustrates the oxidation of
norbornane using H.sub.5IO.sub.6 as the oxidant with catalytic KCl.
Note that yields presented are relative to the amount of
iodine(VII) and are the average of the reaction run at least 3
times.
[0020] FIG. 5.1 is a scheme that illustrates the oxidation of
adamantane using ammonium periodate and catalytic potassium
chloride. The yields presented are relative to the amount of
adamantane in solution.
DETAILED DESCRIPTION
[0021] Before the present disclosure is described in greater
detail, it is to be understood that this disclosure is not limited
to particular embodiments described, as such may, of course, vary.
It is also to be understood that the terminology used herein is for
the purpose of describing particular embodiments only, and is not
intended to be limiting, since the scope of the present disclosure
will be limited only by the appended claims.
[0022] Where a range of values is provided, it is understood that
each intervening value, to the tenth of the unit of the lower limit
(unless the context clearly dictates otherwise), between the upper
and lower limit of that range, and any other stated or intervening
value in that stated range, is encompassed within the disclosure.
The upper and lower limits of these smaller ranges may
independently be included in the smaller ranges and are also
encompassed within the disclosure, subject to any specifically
excluded limit in the stated range. Where the stated range includes
one or both of the limits, ranges excluding either or both of those
included limits are also included in the disclosure.
[0023] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this disclosure belongs.
Although any methods and materials similar or equivalent to those
described herein can also be used in the practice or testing of the
present disclosure, the preferred methods and materials are now
described.
[0024] All publications and patents cited in this specification are
herein incorporated by reference as if each individual publication
or patent were specifically and individually indicated to be
incorporated by reference and are incorporated herein by reference
to disclose and describe the methods and/or materials in connection
with which the publications are cited. The citation of any
publication is for its disclosure prior to the filing date and
should not be construed as an admission that the present disclosure
is not entitled to antedate such publication by virtue of prior
disclosure. Further, the dates of publication provided could be
different from the actual publication dates that may need to be
independently confirmed.
[0025] As will be apparent to those of skill in the art upon
reading this disclosure, each of the individual embodiments
described and illustrated herein has discrete components and
features which may be readily separated from or combined with the
features of any of the other several embodiments without departing
from the scope or spirit of the present disclosure. Any recited
method can be carried out in the order of events recited or in any
other order that is logically possible.
[0026] Embodiments of the present disclosure will employ, unless
otherwise indicated, techniques of chemistry, synthetic organic
chemistry, and the like, which are within the skill of the art.
Such techniques are explained fully in the literature.
[0027] The following examples are put forth so as to provide those
of ordinary skill in the art with a complete disclosure and
description of how to perform the methods and use the compositions
and compounds disclosed and claimed herein. Efforts have been made
to ensure accuracy with respect to numbers (e.g., amounts,
temperature, etc.), but some errors and deviations should be
accounted for. Unless indicated otherwise, parts are parts by
weight, temperature is in .degree. C., and pressure is in bar.
Standard temperature and pressure are defined as 0.degree. C. and 1
bar.
[0028] Before the embodiments of the present disclosure are
described in detail, it is to be understood that, unless otherwise
indicated, the present disclosure is not limited to particular
materials, reagents, reaction materials, manufacturing processes,
or the like, as such can vary. It is also to be understood that the
terminology used herein is for purposes of describing particular
embodiments only, and is not intended to be limiting. It is also
possible in the present disclosure that steps can be executed in
different sequence where this is logically possible. Different
stereochemistry is also possible, such as products of syn or anti
addition could be both possible even if only one is drawn in an
embodiment.
[0029] It must be noted that, as used in the specification and the
appended claims, the singular forms "a," "an," and "the" include
plural referents unless the context clearly dictates otherwise.
Thus, for example, reference to "a support" includes a plurality of
supports. In this specification and in the claims that follow,
reference will be made to a number of terms that shall be defined
to have the following meanings unless a contrary intention is
apparent.
DEFINITIONS
[0030] By "chemically feasible" is meant a bonding arrangement or a
compound where the generally understood rules of organic structure
are not violated. The structures disclosed herein, in all of their
embodiments are intended to include only "chemically feasible"
structures, and any recited structures that are not chemically
feasible, for example in a structure shown with variable atoms or
groups, are not intended to be disclosed or claimed herein.
[0031] The term "substituted" refers to any one or more hydrogen
atoms on the designated atom (e.g., a carbon atom) that can be
replaced with a selection from the indicated group (e.g., halide,
hydroxyl, alkyl, and the like), provided that the designated atom's
normal valence is not exceeded.
[0032] As used herein, an "analog", or "analogue" of a chemical
compound is a compound that, by way of example, resembles another
in structure but is not necessarily an isomer (e.g., 5-fluorouracil
is an analog of thymine).
[0033] As used herein, a "derivative" of a compound refers to a
chemical compound that may be produced from another compound of
similar structure in one or more steps, as in replacement of H by
an alkyl, acyl, or amino group.
[0034] As used herein, "aliphatic" or "aliphatic group" refers to a
saturated or unsaturated, linear or branched, cyclic (non-aromatic)
or heterocyclic (non-aromatic), hydrocarbon or hydrocarbon group
and encompasses alkyl, alkenyl, and alkynyl groups, and alkanes,
alkene, and alkynes, for example.
[0035] As used herein, "alkane" refers to a saturated aliphatic
hydrocarbon which can be straight or branched, having 1 to 40, 1 to
20, 1 to 10, or 1 to 5 carbon atoms, where the stated range of
carbon atoms includes each intervening integer individually, as
well as sub-ranges. Examples of alkane include, but are not limited
to methane, ethane, propane, butane, pentane, and the like.
Reference to "alkane" includes unsubstituted and substituted forms
of the hydrocarbon.
[0036] As used herein, "alkyl" or "alkyl group" refers to a
saturated aliphatic hydrocarbon radical which can be straight or
branched, having 1 to 40, 1 to 20, 1 to 10, or 1 to 5 carbon atoms,
where the stated range of carbon atoms includes each intervening
integer individually, as well as sub-ranges. Examples of alkanes
include, but are not limited to methyl, ethyl, n-propyl, i-propyl,
n-butyl, s-butyl, t-butyl, n-pentyl, and s-pentyl. Reference to
"alkyl" or "alkyl group" includes unsubstituted and substituted
forms of the hydrocarbon group.
[0037] As used herein, "alkene" refers to an aliphatic hydrocarbon
which can be straight or branched, containing at least one
carbon-carbon double bond, having 2 to 40, 2 to 20, 2 to 10, or 2
to 5 carbon atoms, where the stated range of carbon atoms includes
each intervening integer individually, as well as sub-ranges.
Examples of alkene groups include, but are not limited to, ethene,
propene, and the like. Reference to "alkene" includes unsubstituted
and substituted forms of the hydrocarbon.
[0038] As used herein, "alkenyl" or "alkenyl group" refers to an
aliphatic hydrocarbon radical which can be straight or branched,
containing at least one carbon-carbon double bond, having 2 to 40,
2 to 20, 2 to 10, or 2 to 5 carbon atoms, where the stated range of
carbon atoms includes each intervening integer individually, as
well as sub-ranges. Examples of alkenyl groups include, but are not
limited to, ethenyl, propenyl, n-butenyl, i-butenyl,
3-methylbut-2-enyl, n-pentenyl, heptenyl, octenyl, decenyl, and the
like. Reference to "alkyl" or "alkyl group" includes unsubstituted
and substituted forms of the hydrocarbon group.
[0039] As used herein, "alkyne" refers to straight or branched
chain hydrocarbon groups having 2 to 40, 2 to 20, 2 to 10, or 2 to
5 carbon atoms and at least one triple carbon to carbon bond.
Reference to "alkyne" includes unsubstituted and substituted forms
of the hydrocarbon.
[0040] As used herein, "alkynyl" or "alkynyl group" refers to
straight or branched chain hydrocarbon groups having 2 to 40, 2 to
20, 2 to 10, or 2 to 5 carbon atoms and at least one triple carbon
to carbon bond, such as ethynyl. Reference to "alkynyl" or "alkynyl
group" includes unsubstituted and substituted forms of the
hydrocarbon group.
[0041] As used herein, "aromatic" refers to a monocyclic or
multicyclic ring system of 6 to 20 or 6 to 10 carbon atoms having
alternating double and single bonds between carbon atoms. Exemplary
aromatic groups include benzene, naphthalene, and the like.
Reference to "aromatic" includes unsubstituted and substituted
forms of the hydrocarbon.
[0042] As used herein, "aryl" or "aryl group" refers to an aromatic
monocyclic or multicyclic ring system of 6 to 20 or 6 to 10 carbon
atoms. The aryl is optionally substituted with one or more
C.sub.1-C.sub.20 alkyl, alkylene, alkoxy, or haloalkyl groups.
Exemplary aryl groups include phenyl or naphthyl, or substituted
phenyl or substituted naphthyl. Reference to "aryl" or "aryl group"
includes unsubstituted and substituted forms of the hydrocarbon
group.
[0043] The term "substituted," as in "substituted alkyl",
"substituted aryl," "substituted heteroaryl" and the like, means
that the substituted group may contain in place of one or more
hydrogens a group such as alkyl, hydroxy, amino, halo,
trifluoromethyl, cyano, alkoxy, alkylthio, or carboxy.
[0044] As used herein, "halo", "halogen", "halide", or "halogen
radical" refers to a fluorine, chlorine, bromine, iodine, and
astatine, and radicals thereof. Further, when used in compound
words, such as "haloalkyl" or "haloalkenyl", "halo" refers to an
alkyl or alkenyl radical in which one or more hydrogens are
substituted by halogen radicals. Examples of haloalkyl include, but
are not limited to, trifluoromethyl, trichloromethyl,
pentafluoroethyl, and pentachloroethyl.
[0045] As used herein, "cyclic" hydrocarbon refers to any stable 4,
5, 6, 7, 8, 9, 10, 11, or 12 membered, (unless the number of
members is otherwise recited), monocyclic, bicyclic, or tricyclic
cyclic ring.
[0046] As used herein, "heterocycle" refers to any stable 4, 5, 6,
7, 8, 9, 10, 11, or 12 membered, (unless the number of members is
otherwise recited), monocyclic, bicyclic, or tricyclic heterocyclic
ring that is saturated or partially unsaturated, and which includes
carbon atoms and 1, 2, 3, or 4 heteroatoms independently selected
from the group consisting of N, O, and S. If the heterocycle is
defined by the number of carbons atoms, then from 1, 2, 3, or 4 of
the listed carbon atoms are replaced by a heteroatom. If the
heterocycle is bicyclic or tricyclic, then at least one of the two
or three rings must contain a heteroatom, though both or all three
may each contain one or more heteroatoms. The N group may be N, NH,
or N-substituent, depending on the chosen ring and if substituents
are recited. The nitrogen and sulfur heteroatoms optionally may be
oxidized (e.g., S, S(O), S(O).sub.2, and N--O). The heterocycle may
be attached to its pendant group at any heteroatom or carbon atom
that results in a stable structure. The heterocycles described
herein may be substituted on carbon or on a heteroatom if the
resulting compound is stable.
[0047] "Heteroaryl" refers to any stable 5, 6, 7, 8, 9, 10, 11, or
12 membered, (unless the number of members is otherwise recited),
monocyclic, bicyclic, or tricyclic heterocyclic ring that is
aromatic, and which consists of carbon atoms and 1, 2, 3, or 4
heteroatoms independently selected from the group consisting of N,
O, and S. If the heteroaryl is defined by the number of carbons
atoms, then 1, 2, 3, or 4 of the listed carbon atoms are replaced
by a heteroatom. If the heteroaryl group is bicyclic or tricyclic,
then at least one of the two or three rings must contain a
heteroatom, though both or all three may each contain one or more
heteroatoms. If the heteroaryl group is bicyclic or tricyclic, then
only one of the rings must be aromatic. The N group may be N, NH,
or N-substituent, depending on the chosen ring and if substituents
are recited. The nitrogen and sulfur heteroatoms may optionally be
oxidized (e.g., S, S(O), S(O).sub.2, and N--O). The heteroaryl ring
may be attached to its pendant group at any heteroatom or carbon
atom that results in a stable structure. The heteroaryl rings
described herein may be substituted on carbon or on a nitrogen atom
if the resulting compound is stable.
[0048] The term "heteroatom" means for example oxygen, sulfur,
nitrogen, phosphorus, or silicon (including, any oxidized form of
nitrogen, sulfur, phosphorus, or silicon; the quaternized form of
any basic nitrogen or; a substitutable nitrogen of a heterocyclic
ring).
[0049] The term "bicyclic" represents either an unsaturated or
saturated stable 7- to 12-membered bridged or fused bicyclic carbon
ring. The bicyclic ring may be attached at any carbon atom which
affords a stable structure. The term includes, but is not limited
to, naphthyl, dicyclohexyl, dicyclohexenyl, and the like.
[0050] As used herein, the term "purified" and like terms relate to
an enrichment of a molecule or compound relative to other
components normally associated with the molecule or compound in a
native environment. The term "purified" does not necessarily
indicate that complete purity of the particular molecule has been
achieved during the process. A "highly purified" compound as used
herein refers to a compound that is greater than 90% pure.
General Discussion
[0051] Embodiments of the present disclosure provide for methods of
hydrocarbon functionalization, methods and systems for converting a
hydrocarbon into a compound including at least one group ((e.g.,
hydroxyl group) (e.g., methane to methanol)), functionalized
hydrocarbons, and the like.
[0052] Advantages of embodiments of the present disclosure can
include: 1) the use of a simple and inexpensive catalyst (e.g.,
A.sub.aX.sub.n such as sodium chloride (table salt)), 2)
iodine-based compound oxidants that can be thermally regenerated
using oxygen in air (e.g., iodate, periodate, I(III) reagents), 3)
fast conversion of alkanes, 4) low temperatures (e.g., about 100 to
250.degree. C.), 5) selectivity toward mono-functionalized product,
and 6) the use of sources of functionalization (e.g., acids) that
are more weakly acidic than oleum (e.g., trifluoroacetic acid,
acetic acid, water) or halogens.
[0053] In an embodiment, alkanes can be converted to
mono-functionalized esters in good yields with the use of salts
(e.g., chloride salts (in catalytic amounts)) and with iodine-based
compound as the sole oxidant in source of functionalization (e.g.,
iodate or periodate). In one aspect, the system operates over a
large range of pressures (e.g., about 240-6900 kPa) and
temperatures (e.g., about 100-235.degree. C.) and at short reaction
times (often about 2 hours or less) and exhibits excellent
selectivity for monofunctionalized products. Embodiments of the
present disclosure can provide for conversions of methane to
MeTFA>20% (TFA=trifluoroacetate), conversion of ethane can be
even more efficient with about 30% yield of EtTFA, and propane
conversion can occur>20% yield. The values for alkane conversion
disclosed herein meet many of the established benchmarks for
efficient alkane functionalization. In addition, the distinct
reactivity imparted by chloride (compared with I.sub.2,
IO.sub.3.sup.-, I(TFA).sub.3, etc. with no chloride) disclosed
herein is unique and without precedent, resulting in substantial
increases in efficiency for production of mono-functionalized
alkanes. An additional benefit of the present disclosure is that
iodine (e.g., the byproduct of KCl/IO.sub.3.sup.- oxidation
reactions) can be reoxidized to iodate in basic aqueous solution
with molecular oxygen.
[0054] An embodiment of the present disclosure includes methods of
making a compound including at least one group such as, but not
limited to, hydroxyl, halide, carbonyl and a combination thereof
(e.g., glycols, carboxylic acids), using hydrocarbons, such as
those present in natural gas. In an embodiment, the compound
including at least one group can include a combination of groups
selected from hydroxyl, halide, or carbonyl. In an embodiment, the
method can include mixing a salt (A.sub.aX.sub.n), an iodine-based
compound, and a source of functionalization to form a first mixture
and then mixing the first mixture with a hydrocarbon in the gas
phase to make a functionalized hydrocarbon. Subsequently, the
functionalized hydrocarbon can be converted to an alcohol, glycol,
amine or a combination thereof and the source of functionalization,
where the source of functionalization can be recycled.
[0055] In an embodiment, the salt, the iodine-based compound, and
the source of functionalization can be added (e.g., separately,
mixed prior to introduction and then added, or simultaneously
added) to a reaction vessel to form a first mixture and then the
hydrocarbon can be added to the reaction vessel. In an embodiment,
the reaction vessel can be pressurized with a gas sufficient to
provide an internal pressure of about 103 kPa (15 psi) to 10343 kPa
(1500 psi) or about 240 kPa (35 psi) to 5516 kPa (800 psi) using a
pressure system. In an embodiment, the gas used to obtain this
pressure are methane, ethane, propane, butane, carbon dioxide,
nitrogen, helium, argon, neon, carbon monoxide, hydrogen, oxygen,
air, the hydrocarbon itself, or mixtures thereof. In an embodiment,
the pressure system can include pumps, valves, metering gauges,
computer system, and the like to accomplish flowing gas into and
out of the vessel.
[0056] In an embodiment, the reaction vessel can be heated to a
temperature of about 25 to 300.degree. C. or about 130 to
230.degree. C. using a temperature system. In an embodiment, the
temperature system can include heating elements and a computer
system to control the heat within the vessel. The temperature can
be maintained over a period of about 10 minutes to 5 days or 20
minutes to 5 hours in order to contact the hydrocarbon with the
salt, the iodine-based compound, the source of functionalization
and pressurization gas to generate a mixture including the
functionalized hydrocarbon formed from the hydrocarbon and an
adduct of the source of functionalization. In an embodiment, the
vessel can include a system to mix the contents of the vessel.
[0057] In an embodiment, the hydrocarbon can be aliphatic or
aromatic, substituted or unsubstituted, having 1 to 40 carbon
atoms. In an embodiment, the aliphatic hydrocarbon can be saturated
or unsaturated, linear, branched, or cyclic. In an embodiment, the
hydrocarbon can be a hydrocarbon that is in the gas phase at room
temperature. In an embodiment, the hydrocarbon can be in a purified
form or a mixture of multiple hydrocarbons (e.g., natural gas). An
embodiment of the hydrocarbon can include methane, ethane, propane,
butane, benzene, toluene, naphthalene, norbornane, adamantane and a
mixture thereof.
[0058] In an embodiment, the compound including at least one
hydroxyl group can be an alcohol or glycol of the hydrocarbons
noted herein. For example, the compound can be methanol, ethanol,
propanol, butanol, ethylene glycol, propylene glycol, and the
like.
[0059] In an embodiment, the compound including at least one
halide, can be chloromethane, iodomethane, chloroethane,
1,2-dichloroethane, iodoethane, 1,2-diiodoethane, chloropropane,
1,2-dichloropropane, 1,3-dichloropropane, iodopropane,
1,2-iodopropane, 1,3-diiodopropane and the like.
[0060] In an embodiment, the compound including at least one
carbonyl group, can be a methyl ester, ethyl ester, propyl ester
and the like.
[0061] In an embodiment, the alkane conversion can be about 15% to
30% with selectivity of up to about 98%, in a 1 or 2 hour reaction.
For example, ethane can be converted to monofunctionalized ethyl
product in about 30% conversion with about 98% selectivity. In
another example, functionalized methyl product can be formed from
methane with about 10% to 25% conversion with up to about 90%
selectivity.
[0062] As noted above, the salt can be represented by
A.sub.aX.sub.n. In an embodiment, "A" can represent an element or
combination of elements capable of maintaining a formal positive
charge. In an embodiment A.sub.aX.sub.n, can be a salt such as a
halide salt. In an embodiment, "A" can be: hydrogen, lithium,
sodium, potassium, beryllium, magnesium, calcium, strontium,
barium, transition metals, aluminum, gallium, thallium, indium,
tin, sulfur, ammonium (NH.sub.4.sup.+), alkylammonium. phosphonium
(PH.sub.4.sup.+), alkylphosphonium, arylphosphonium, or trimethyl
sulfonium ([S(CH.sub.3).sub.3].sup.+). In an embodiment, X can be
chloride. In an embodiment, subscript "a" can represent the
oxidation state of "X" and subscript "n" can represent the
oxidation state of "A". In an embodiment A.sub.aX.sub.n, can be:
HCl, NaCl, KCl, CaCl.sub.2, LiCl, ZnCl.sub.2, BeCl.sub.2,
MgCl.sub.2, PCl.sub.3, NH.sub.4Cl, CCl.sub.4, CHCl.sub.3,
transition metal chlorides, main group metal chlorides or
organochlorides. These compounds are available for purchase from
commercial suppliers, can be prepared from reported procedures, can
be prepared in situ by reaction elements with halogen sources and
from natural saline solutions.
[0063] In an embodiment, the iodine-based compound can include an
iodate, periodate, iodine oxide (such as diiodine tetroxide, iodine
monoxide, diiodine pentoxide, iodine monoxide or tetraiodine
nonoxide), iodosyl (IO.sup.+), trivalent iodine compound such
I(TFA).sub.3, and a combination thereof. In an embodiment, the
iodate can be represented by Q(IO.sub.3).sub.p. In an embodiment
"Q" can be: hydrogen, lithium, sodium, potassium, beryllium,
magnesium, calcium, strontium, barium, transition metals, aluminum,
gallium, thallium, indium, tin, sulfur, ammonium (NH.sub.4.sup.+),
alkylammonium. phosphonium (PH.sub.4.sup.+), alkylphosphonium,
arylphosphonium, or trimethyl sulfonium
([S(CH.sub.3).sub.3].sup.+). Subscript "p" can be 1 to 5.
[0064] In an embodiment, the iodine-based compound can include
Q.sub.o(IO.sub.4).sub.p. In an embodiment "Q" can behydrogen,
lithium, sodium, potassium, beryllium, magnesium, calcium,
strontium, barium, transition metals, aluminum, gallium, thallium,
indium, tin, sulfur, ammonium (NH.sub.4.sup.+), alkylammonium.
phosphonium (PH.sub.4.sup.+), alkylphosphonium, arylphosphonium, or
trimethyl sulfonium ([S(CH.sub.3).sub.3].sup.+). Subscript "o" can
be 1 and subscript "p" can be 1 to 5.
[0065] In an embodiment, the iodine-based compound can include
H.sub.5(IO.sub.6).
[0066] In particular, the iodine-based compound can be: KIO.sub.3,
Ca(IO.sub.3).sub.2, Ba(IO.sub.3).sub.2, Cu(IO.sub.3).sub.2,
NH.sub.4IO.sub.3, KIO.sub.4, NaIO.sub.4 and NH.sub.4IO.sub.4,
I(TFA).sub.3, I.sub.2O.sub.5, [IO].sup.+, [IO.sub.2].sup.+, and a
combination thereof. The iodine-based compound, such as iodates,
can be purchased commercially, prepared through reported procedures
or generated in situ by means which include but are not limited to
chemically, thermally, electrochemically, or though photolysis.
[0067] In an embodiment, the source of functionalization can
include a solvent that can be used to functionalize the
hydrocarbon. In an embodiment, the source of functionalization can
be: trifluoroacetic acid, trifluoroacetic anhydride,
hexafluorobutyric acid, water, sulfuric acid, supercritical carbon
dioxide, acetic acid, and a combination thereof.
[0068] In an embodiment, the functionalized hydrocarbon can include
methyl trifluoroacetate ester, methyl acetate, methanol,
chloromethane, iodomethane, dimethylcarbonate, 1,2-dichloroethane,
1,2-diiodoethane, 1,2-dichloropropane, 1,3-dichloropropane,
1,2-iodopropane, 1,3-diiodopropane ethyl trifluoroacetate ester,
ethyl acetate, ethanol, ethyl chloride, ethyl iodide, ethylene
glycol, ethylene esters, propyl trifluoroacetate ester, propyl
acetate, propanol, propyl chloride, propyl iodide, propylene
glycol, propylene esters, or a combination thereof.
[0069] In an embodiment, the amount of A.sub.aX.sub.n and
iodine-based compound that are combined with the source of
functionalization can vary and can be about 0.001% to 100% as
compared to the mass of the source of functionalization. In
particular, the mass of the A.sub.aX.sub.n can be about 0.14% to
10% as compared to the mass of the source of functionalization and
the mass for the oxidant can be about 17%-26% as compared to the
mass of the source of functionalization.
[0070] In an embodiment, A.sub.aX.sub.n can be about 0.2 to 25
weight % or about 0.3 to 5 weight % of the first mixture. In an
embodiment, the iodine-based compound can be about 2 to 40 weight %
or about 5 to 25 weight % of the first mixture. In an embodiment,
the source of functionalization can be about 30 to 95 weight % or
about 60 to 90 weight % of the first mixture. In an embodiment, the
amount of the hydrocarbon relative to the first mixture can be
about 0.01 to 20 weight % or about 0.1 to 5 weight %.
[0071] In a particular embodiment, the salt (A.sub.aX.sub.n), the
iodine-based compound, and the source of functionalization are
disposed into a vessel to which is added a volume of methane. The
purity of methane may be varied from 100% to mixtures such as that
found in natural gas, crude oil, shale, and sources formed from
known reported processes. The ratio of hydrocarbon relative to
A.sub.aX.sub.n can be about 1 to 1.times.10.sup.6. The vessel is
then pressurized with a gas sufficient to produce a pressure of
about 35 to 1500 psi. The vessel is then heated to a temperature of
about 100 to 235.degree. C. for about 1 to 3 hours. Additional
components of the reaction can be added intermittently to maintain
production of the functionalized hydrocarbon. In addition, the
mixture can be stirred during a portion or all of the time of the
reaction.
[0072] In an embodiment, a combination of potassium chloride,
potassium iodate, methane (800 psi) and trifluoroacetic acid are
heated to about 180.degree. C. for about three hours. The product
methyl trifluoroacetate (.about.0.5 M) is the exclusive product
with nearly 10% methane conversion. Other embodiments are described
in the Examples.
[0073] In the case of utilizing water as the functionalization
source, the alcohol is separated from the reaction mixture by a
suitable means such as distillation. In other cases such as when
the functionalization source is trifluoroacetic acid, the
functionalized hydrocarbon methyl trifluoroacetate, can be
separated from the reaction mixture by a suitable means such as
distillation. The functionalized product, e.g., methyl
trifluoroacetate is hydrolyzed to produce free alcohol and
regenerate the functionalization source. Although it is understood
that the process is not limited to methyl trifluoroacetate, the
methyl trifluoroacetate is introduced to the hydrolysis reaction
along with water in at least a stoichiometric amount to fully
convert the functionalized product.
[0074] A large number of acidic and basic sources are known to
promote hydrolysis. Suitable basic sources can include sodium
hydroxide, potassium hydroxide, basic alumina and any combinations
thereof. The preferred method of hydrolysis is acidic means as this
allows for easy separation of the alcohol. Examples of acid sources
can include hydrochloric acid, iodic acid, sulfuric acid, acidic
alumina.
[0075] Separation of the alcohol can be accomplished though
distillation, adsorption, extraction and diffusion through a
membrane. Separation of the source of functionalization can be
achieved by similar methods. The source of functionalization can
then be recycled.
[0076] In addition to batch mode the process can be conducted in a
continuous mode as follows. The hydrocarbon, salt, iodine-based
compound, functionalization source, and/or pressurization gas are
introduced via a liquid phase pump, compressor or solid addition
mechanism to a stirred high-pressure reactor. Gas and liquids can
be removed from the reactor continuously at a rate to maintain the
liquid level and total pressure of the reactor. The removed
gas/liquid stream can be transferred to a vessel where the gas and
liquid are separated and one or both streams may be subjected to
further separation or returned to the high-pressure reactor.
EXAMPLES
[0077] Now having described the embodiments of the disclosure, in
general, the examples describe some additional embodiments. While
embodiments of the present disclosure are described in connection
with the example and the corresponding text and figures, there is
no intent to limit embodiments of the disclosure to these
descriptions. On the contrary, the intent is to cover all
alternatives, modifications, and equivalents included within the
spirit and scope of embodiments of the present disclosure.
Example 1
[0078] Potassium iodate (483 mg, 2.26 mmol), potassium chloride
(25.2 mg, 0.338 mmol), trifluoroacetic acid (2.0 mL, 26.1 mmol),
and a magnetic stir bar were loaded into a glass 7 mL glass liner.
The liner was placed into a custom-built 7 cm.sup.3 high-pressure
reactor. The reactor was assembled and pressurized with methane to
500 psi (9.78 mmol) and then with argon to a total pressure of 800
psi. The reactor was heated to 180.degree. C. for 3 hours with
stirring at 10 Hz. After the reactor was cooled to room temperature
the gas was discharged and an internal standard of cyclopentane was
added to the reaction. The liquid was analyzed by .sup.1H nuclear
magnetic resonance (NMR) spectroscopy (FIG. 1.1), .sup.13C NMR
spectroscopy (FIG. 1.2), and gas chromatography-mass spectrometry
(GC-MS) (FIG. 1.3). The percent yield was based on methyl
trifluoroacetate ester product isolated divided by oxidant and
methane substrate introduced into the system. The reaction yielded
97% yield based on oxidant and 24% yield based on methane.
Calculation of % Yield for Example 1:
[0079] If the integral of cyclopentane is equal to 10 then it
follows that:
mmol MeTFA = integral of MeTFA 3 .times. mmol cyclopentane
##EQU00001## 10 L cyclopentane = 0.107 mmol cyclopentane
##EQU00001.2## therefore ##EQU00001.3## 61.15 3 .times. 0.107 mmol
cyclopentane = 2.18 mmol MeTFA ##EQU00001.4## and ##EQU00001.5##
2.26 mmoles KIO 3 and 9.78 mmol CH 4 used in reaction
##EQU00001.6## and ##EQU00001.7## 2.18 mmol MeTFA 2.26 mmol KIO 3
.times. 100 = 97 % yield based on oxidant ##EQU00001.8## and
##EQU00001.9## 2.18 mmol MeTFA 9.78 mmol CH 4 .times. 100 = 24 %
yield based on methane ##EQU00001.10##
Example 2
[0080] Calcium iodate (441 mg, 1.13 mmol), potassium iodide (56.1
mg, 0.338 mmol), trifluoroacetic acid (2.0 mL, 26.1 mmol), and a
magnetic stir bar were loaded into a glass 7 mL glass liner. The
liner was placed into a custom-built 7 cm.sup.3 high-pressure
reactor. The reactor was assembled and pressurized with methane to
500 psi (9.78 mmol) and then with argon to a total pressure of 800
psi. The reactor was heated to 180.degree. C. for 3 hours with
stirring at 10 Hz. After the reactor was cooled to room temperature
the gas was discharged and an internal standard of cyclopentane was
added to the reaction. The liquid was analyzed by .sup.1H nuclear
magnetic resonance (NMR) spectroscopy, .sup.13C NMR spectroscopy,
and gas chromatography-mass spectrometry (GC-MS). The percent yield
was based on methyl trifluoroacetate ester product isolated divided
by oxidant and methane substrate introduced into the system. The
reaction yielded 6% yield based on oxidant and 1% yield based on
methane.
Example 3
[0081] Ammonium iodate (436 mg, 2.26 mmol), lithium bromide (29.4
mg, 0.338 mmol), trifluoroacetic acid (2.0 mL, 26.1 mmol), and a
magnetic stir bar were loaded into a glass 7 mL glass liner. The
liner was placed into a custom-built 7 cm.sup.3 high-pressure
reactor. The reactor was assembled and pressurized with methane to
500 psi (9.78 mmol) and then with argon to a total pressure of 800
psi. The reactor was heated to 180.degree. C. for 3 hours with
stirring at 10 Hz. After the reactor was cooled to room temperature
the gas was discharged and an internal standard of cyclopentane was
added to the reaction. The liquid was analyzed by .sup.1H nuclear
magnetic resonance (NMR) spectroscopy, .sup.13C NMR spectroscopy,
and gas chromatography-mass spectrometry (GC-MS). The percent yield
was based on methyl trifluoroacetate ester product isolated divided
by oxidant and methane substrate introduced into the system. The
reaction yielded 3% yield based on oxidant and 1% yield based on
methane.
Example 4
[0082] Silver iodate (639 mg, 2.26 mmol), zinc chloride (46.1 mg,
0.338 mmol), trifluoroacetic acid (2.0 mL, 26.1 mmol), and a
magnetic stir bar were loaded into a glass 7 mL glass liner. The
liner was placed into a custom-built 7 cm.sup.3 high-pressure
reactor. The reactor was assembled and pressurized with methane to
500 psi (9.78 mmol) and then with argon to a total pressure of 800
psi. The reactor was heated to 180.degree. C. for 3 hours with
stirring at 10 Hz. After the reactor was cooled to room temperature
the gas was discharged and an internal standard of cyclopentane was
added to the reaction. The liquid was analyzed by .sup.1H nuclear
magnetic resonance (NMR) spectroscopy, .sup.13C NMR spectroscopy,
and gas chromatography-mass spectrometry (GC-MS). The percent yield
was based on methyl trifluoroacetate ester product isolated divided
by oxidant and methane substrate introduced into the system. The
reaction yielded 22% yield based on oxidant and 1.5% yield based on
methane.
Example 5
[0083] Copper (II) iodate (467 mg, 1.13 mmol), sodium chloride (4.0
mg, 0.069 mmol), trifluoroacetic acid (2.0 mL, 26.1 mmol), and a
magnetic stir bar were loaded into a glass 7 mL glass liner. The
liner was placed into a custom-built 7 cm.sup.3 high-pressure
reactor. The reactor was assembled and pressurized with methane to
800 psi (15.6 mmol). The reactor was heated to 180.degree. C. for 3
hours with stirring at 10 Hz. After the reactor was cooled to room
temperature the gas was discharged and an internal standard of
cyclopentane was added to the reaction. The liquid was analyzed by
.sup.1H nuclear magnetic resonance (NMR) and .sup.13C NMR
spectroscopy. The percent yield was based on methyl
trifluoroacetate ester product isolated divided by oxidant and
methane substrate introduced into the system. The reaction yielded
45% yield based on oxidant and 3.3% yield based on methane.
Example 6
[0084] Barium iodate (571 mg, 2.26 mmol), carbon tetrachloride
(21.9 .mu.L, 0.338 mmol), trifluoroacetic acid (2.0 mL, 26.1 mmol),
and a magnetic stir bar were loaded into a glass 7 mL glass liner.
The liner was placed into a custom-built 7 cm.sup.3 high-pressure
reactor. The reactor was assembled and pressurized with methane to
500 psi (9.78 mmol) and then with argon to a total pressure of 800
psi. The reactor was heated to 180.degree. C. for 3 hours with
stirring at 10 Hz. After the reactor was cooled to room temperature
the gas was discharged and an internal standard of cyclopentane was
added to the reaction. The liquid was analyzed by .sup.1H nuclear
magnetic resonance (NMR) spectroscopy, .sup.13C NMR spectroscopy,
and gas chromatography-mass spectrometry (GC-MS). The percent yield
was based on methyl trifluoroacetate ester product isolated divided
by oxidant and methane substrate introduced into the system. The
reaction yielded 45% yield based on oxidant and 5% yield based on
methane.
Example 7
[0085] Potassium iodate (483 mg, 2.26 mmol), potassium chloride
(25.2 mg, 0.338 mmol), trifluoroacetic acid (2.0 mL, 26.1 mmol),
and a magnetic stir bar were loaded into a glass 7 mL glass liner.
The liner was placed into a custom-built 7 cm.sup.3 high-pressure
reactor. The reactor was assembled and pressurized with methane to
500 psi (9.78 mmol) and then with argon to a total pressure of 800
psi. The reactor was heated to 180.degree. C. for 3 hours with
stirring at 10 Hz. After the reactor was cooled to room temperature
the gas was discharged and an internal standard of cyclopentane was
added to the reaction. The liquid was analyzed by .sup.1H nuclear
magnetic resonance (NMR) spectroscopy, .sup.13C NMR spectroscopy,
and gas chromatography-mass spectrometry (GC-MS). The percent yield
was based on methyl trifluoroacetate ester product isolated divided
by oxidant and methane substrate introduced into the system. The
reaction yielded 80% yield based on oxidant and 5.8% yield based on
methane.
Example 8
[0086] Sodium iodate (223 mg, 1.13 mmol), sodium chloride (4.0 mg,
0.069 mmol), trifluoroacetic acid (2.0 mL, 26.1 mmol), and a
magnetic stir bar were loaded into a glass 7 mL glass liner. The
liner was placed into a custom-built 7 cm.sup.3 high-pressure
reactor. The reactor was assembled and pressurized with methane to
800 psi (15.6 mmol). The reactor was heated to 180.degree. C. for 3
hours with stirring at 10 Hz. After the reactor was cooled to room
temperature the gas was discharged and an internal standard of
cyclopentane was added to the reaction. The liquid was analyzed by
.sup.1H NMR and .sup.13C NMR spectroscopy. The percent yield was
based on methyl trifluoroacetate ester product isolated divided by
oxidant and methane substrate introduced into the system. The
reaction yielded 59% yield based on oxidant and 4.2% yield based on
methane.
Example 9
[0087] Potassium iodate (726 mg, 3.39 mmol), potassium chloride
(25.2 mg, 0.338 mmol), water (2.0 mL, 111.1 mmol), and a magnetic
stir bar were loaded into a glass 7 mL glass liner. The liner was
placed into a custom-built 7 cm.sup.3 high-pressure reactor. The
reactor was assembled and pressurized with methane to 500 psi (9.78
mmol) methane and then with argon to a total pressure of 800 psi.
The reactor was heated to 180.degree. C. for 3 hours with stirring
at 10 Hz. After the reactor was cooled to room temperature the gas
was discharged and an internal standard of cyclopentane was added
to the reaction. The liquid was analyzed by .sup.1H NMR and
.sup.13C NMR spectroscopy. The percent yield was based on methyl
trifluoroacetate ester product isolated divided by oxidant and
methane substrate introduced into the system. The reaction yielded
1% yield based on oxidant and 0.2% yield based on methane.
Example 10
[0088] Potassium iodate (483 mg, 3.39 mmol), potassium chloride
(25.2 mg, 0.338 mmol), trifluoroacetic acid (2.0 mL, 26.1 mmol),
and a magnetic stir bar were loaded into a glass 7 mL glass liner.
The liner was placed into a custom-built 7 cm.sup.3 high-pressure
reactor. The reactor was assembled and pressurized with ethane to
340 psi (9.74 mmol) and then with argon to a total pressure of 800
psi. The reactor was heated to 180.degree. C. for 3 hours with
stirring at 10 Hz. After the reactor was cooled to room temperature
the gas was discharged and an internal standard of cyclopentane was
added to the reaction. The liquid was analyzed by .sup.1H NMR and
.sup.13C NMR spectroscopy. The percent yield was based on methyl
trifluoroacetate ester product isolated divide by oxidant and
methane substrate introduced into the system. The reaction yielded
26% yield based on oxidant and 6% yield based on ethane.
Example 11
[0089] KCl (0.676 mmol), 7.7 mmol NH.sub.4IO.sub.3 and 8.0 mL of
trifluoroacetic acid were loaded into the reactor. After the
reactor was sealed, it was purged 3 times with ethane and then
charged with 2070 kPa of ethane (6.7 mmol ethane). The reactor was
weighed and subsequently heated and stirred for 1 hour. The reactor
was removed from the heating block and cooled to room temp for 30
min. The resultant gas was collected in a gas bag and analyzed by
GC-TCD. A standard of 30 mL of HOAc or methylene chloride was added
to the reaction liquid. The mixture was stirred, then a sample was
removed for analysis. The products were analyzed by .sup.1H NMR and
GC-MS. 2.03 mmol EtTFA; 0.13 mmol EtCl and 0.06 mmol
1,2-bis(trifluoroacetyl)ethane (glycol) were formed in the
reaction.
Example 12
[0090] KCl (0.676 mmol), 7.7 mmol NH.sub.4IO.sub.3 and 8.0 mL of
trifluoroacetic acid were loaded into the reactor. After the
reactor was sealed, it was purged 3 times with propane and finally
charged with 830 kPa propane (3.0 mmol propane). The reactor was
weighed and subsequently heated and stirred for 2 h. The reactor
was removed from the heating block, cooled to room temp. The
resultant gas was collected in a gas bag and analyzed by GC-TCD. A
standard of 30 mL of HOAc was added to the reaction liquid. The
mixture was stirred, after which a sample was removed for analysis.
The products were analyzed identified by .sup.1H NMR and GC-MS. 121
mmol of 1-trifluoroacetopropane, 404 mmol of
2-trifluoroacetopropane and 236 mmol of
bis(1,2-trifluoroaceto)propane were formed in the reaction.
Example 13
[0091] Methane, a stir bar, 0.676 mmol KCl, 7.7 mmol
NH.sub.4(IO.sub.3) and 8.0 mL of trifluoroacetic acid were loaded
into the 16.1 mL VCO reactor that contained a tight fitting Teflon
liner. After the reactor was sealed and weighed, it was purged
three times with CH.sub.4/Ne. The reaction was pressurized to 340
kPa O.sub.2 (0.8 mmol O.sub.2) and finally pressurized to 3450 kPa
of 90 mol % CH.sub.4/10 mol % Ne (7.6 mmol CH.sub.4). The reactor
was subsequently heated and stirred (800 rpm) for 1 hour. The
reactor was removed from the heating block, placed in front of a
fan and cooled to room temp for 30 min. The resultant gas was
collected in a gas bag and analyzed by GC-TCD. A standard of 30 mL
of HOAc and/or 30 mL of methylene chloride was added to the
reaction liquid. The mixture was stirred, then a sample was removed
for analysis. The products were analyzed by .sup.1H NMR, .sup.13C
NMR and GC-MS. 1.73 mmol MeTFA and 0.06 mmol of MeCl were formed.
The reaction with ethane and oxygen were charged first with 255 kPa
O.sub.2 then filled to a final pressure of 2070 kPa with ethane.
The reaction was then carried out as described above.
Example 14
[0092] Potassium periodate (1.77 g, 7.7 mmol), potassium chloride
(50 mg, 0.67 mmol), trifluoroacetic acid (8.0 mL, 104.4 mmol), and
a magnetic stir bar were loaded into a 12 mL teflon liner. The
liner was placed into a custom-built 16 cm.sup.3 high-pressure
reactor. The reactor was assembled and three times purged with
CH.sub.4/Ne (9:1) to 500 psi, then filled with a total pressure of
500 psi. The reactor was heated to 200.degree. C. for 1 hour with
stirring at 10 Hz. After the reactor was cooled to room
temperature, the gas was discharged and an internal standard of
1,2-dichloroethane or dichloromethane was added to the reaction.
The liquid was analyzed by .sup.1H nuclear magnetic resonance (NMR)
spectroscopy (FIG. 3.1) and gas chromatography (with flame
ionization detector) spectrometry (GC-FID). The reaction yielded
1.7 mmol of methyl trifluoroacetate.
Example 15
[0093] Potassium periodate (115 mg, 0.5 mmol), potassium chloride
(6 mg, 0.08 mmol), trifluoroacetic acid (2.5 mL, 32.6 mmol), and a
magnetic stir bar were loaded into a custom-built 7 cm.sup.3
high-pressure reactor. The reactor was assembled and three times
purged with CH.sub.4/Ne (9:1) to 500 psi, then filled with a total
pressure of 500 psi. The reactor was heated to 150.degree. C. for 2
hours with stirring at 10 Hz. After the reactor was cooled to room
temperature the gas was discharged and an internal standard of
1,2-dichloroethane was added to the reaction. The liquid was
analyzed by .sup.1H nuclear magnetic resonance (NMR) spectroscopy
and gas chromatography (with flame ionization detector)
spectrometry (GC-FID). The reaction yielded 0.18 mmol of methyl
trifluoroacetate.
Example 16
[0094] An 8 mL microwave vial equipped with a stirbar was charged
with norbornane (2.5 mmol), orthoperiodic acid (0.25 mmol), TFA (4
mL), and trifluoroacetic anhydride (4.2 mmol). The vial was then
crimped shut and heated to 60.degree. C. for 18 h with vigorous
stirring. The entire reaction is added to 4 mL of chloroform.
Dodecane (0.25 mmol) was added as an internal standard. The
reaction was then extracted with water (3.times.5 mL) and the
organic washings dried over MgSO.sub.4. The reaction was analyzed
via GC-MS relative to the internal standard yielding norbornyl
trifluoroacetate in 208.+-.4% yield (n=3) relative to the amount of
iodine(VII). Addition of potassium chloride in a separate run gave
similar yields (.about.200%) yet required much shorter reaction
times (3 h). FIG. 4.1 is a scheme illustrating the oxidation of
norbornane using H.sub.5IO.sub.6 as the oxidant with catalytic
KCl.
Example 17
[0095] An 8 mL microwave vial equipped with a stirbar was charged
with adamantane (1.0 mmol), ammonium periodate (1.0 mmol), and KCl
(0.15 mmol). TFA (4 mL) was added and the vial sealed with a crimp
cap. The mixture was then stirred at 60 C for 1 hour at which point
the vial was allowed to cool. The entire reaction was added to 4 mL
of chloroform. Dodecane (1.0 mmol) was added as an internal
standard. The reaction was then extracted with water (3.times.5 mL)
and the organic washings dried over MgSO.sub.4. The reaction was
analyzed via GC-MS relative to the internal standard yielding
1-adamantyl trifluoroacetate in 58.+-.2% yield, based on starting
adamantane, as the only product. The control reaction without
chloride showed only trace amounts of product. FIG. 5.1 is a scheme
that illustrates the oxidation of adamantane using ammonium
periodate and catalytic potassium chloride.
Introduction:
[0096] Natural gas is a chemical feedstock and a primary fuel that
accounts for nearly 25% of the world's energy..sup.1 A significant
amount of natural gas is "stranded". However, the expense of
infrastructure associated with pipelines or liquefaction often make
transportation uneconomical..sup.2 The Global Gas Flaring Reduction
Partnership estimates that 140 billion cubic meters of natural gas
are flared or vented annually..sup.3 New gas to liquid (GTL)
technologies that efficiently convert alkanes from natural gas into
easily transportable liquids would allow utilization of this vast
hydrocarbon resource.
[0097] New chemistry is needed for the direct conversion of gaseous
alkanes to liquid alcohols..sup.4 The conversion of alkanes and
oxygen to alcohols is thermodynamically favorable (by .about.30
kcal/mol for methane/1/2O.sub.2 to methanol), but the large
activation barriers associated with breaking strong (.about.100-105
kcal/mol).sup.5 non-polar C--H bonds of alkanes and relatively
lower barriers for reaction of the alcohol products make direct
conversion difficult..sup.6 As a result, even modern methods for
alkane functionalization involve indirect and energy-intensive
processes. For example, the conversion of methane to methanol by
current technologies requires methane reforming to generate a
mixture of carbon monoxide and dihydrogen (syngas) followed by
conversion of syngas to methanol. The ethane, propane and butane
portions of natural gas can be converted to olefins by high
temperature (.about.850.degree. C.) cracking. Reactions that could
enable the direct conversion of alkanes from natural gas to
partially oxidized products under more moderate conditions have
been highly sought..sup.6-11 In particular, the preparation of
mono-functionalized species (RX) at temperatures.ltoreq.250.degree.
C. and pressures.ltoreq.3500 kPa would allow less energy intensive
and capital intensive GTL conversions. Radical-based chemistry
provides a platform to cleave strong alkane C--H bonds; however,
the oxidized products are typically more reactive than the starting
alkane..sup.6 Accordingly, over oxidation has been an issue for
catalytic oxychlorination reactions,.sup.12-16 which involve
passing mixtures of CH.sub.4, HCl and O.sub.2 over a catalyst bed
at temperatures>350.degree. C..sup.17,18 The direct use of
halogens to produce MeX has also been developed..sup.19-22
[0098] Another option for direct alkane partial oxidation is based
on the use of transition metals. Biomimetic approaches for C--H
functionalization using high valent oxo complexes have been
reported..sup.23-30 Another method is the use of transition metals
that directly coordinate and activate C--H bonds..sup.7,8,31-36
This strategy has been used to functionalize alkanes by
metal-mediated alkane dehydrogenation..sup.37-42 Also,
electrophilic late transition metal complexes (e.g., Pt, Pd, Hg and
Au) have been shown to catalyze methane functionalization in super
acidic media..sup.43-47 Product inhibition and product separation
turned out to be significant challenges for these processes. The
use of main group metals for alkane functionalization that do not
require super acids has been reported recently..sup.48
Metal-mediated transformations that likely involve radicals have
also been reported..sup.49-51 In an alternative approach, Ag
complexes catalyze conversions of alkanes to esters using ethyl
diazoacetate..sup.52,53
[0099] Hypervalent iodine species.sup.54-56 are also capable of
functionalizing non-polar C--H bonds through electrophilic,
non-radical pathways..sup.21,22,57-60 I.sub.2.sup.61-64 and
KIO.sub.3.sup.64 convert methane to MeOSO.sub.3H in the super
acidic medium H.sub.2SO.sub.4 and SO.sub.3 (oleum)..sup.63 Other
halogen-based systems (e.g., I(TFA).sub.3).sup.44 have been
demonstrated to functionalize hydrocarbons with low selectivity to
esters..sup.17,45,46,63 An efficient process for alkane C--H
oxygenation has remained an elusive goal. We describe here a
selective reaction of methane and higher alkanes with hypervalent
iodine species mediated by catalytic quantities of chloride in
weaker acid media such as HTFA, aqueous HTFA, acetic acid and
water.
Results and Discussion:
[0100] We have identified a hypervalent iodine-based system that
effectively and selectively oxidizes methane, ethane and propane in
non-super acid media to the corresponding alcohol esters (eq 1).
The reactions occur with selectivity for mono-functionalized
product. Methane is converted over a broad range of pressures
(240-6900 kPa) and at temperatures.ltoreq.235.degree. C.
Significantly, the system requires sub-stoichiometric amounts of
chloride to generate the active species that reacts with the
alkanes. In the absence of chloride the reaction is inefficient
and/or unselective. The iodate/chloride system is much more
efficient than the hypervalent iodine systems without chloride such
as I.sub.2, iodate or I(TFA).sub.3. This suggests that the
iodate/chloride process functions via a different mechanism than
these systems (see below).
##STR00001##
[0101] Pressurizing a mixture of KCl (0.676 mmol) and
NH.sub.4IO.sub.3 (7.70 mmol) in HTFA to 3450 kPa with methane (8.4
mmol) and heating at 180.degree. C. for 1 h, results in the
formation of 1.81 mmol of MeX (X=TFA or Cl) in about 20% yield (eq
2). Yields are based on total methane present as determined by
weighing reactors before and after methane addition. The presence
of chloride is essential to the reaction (see below), and the use
of sub-stoichiometric quantities (based on iodate or methane
converted) suggests that chloride might play a catalytic role.
##STR00002##
[0102] MeTFA was found to be relatively stable under the reaction
conditions. In reactions where 0.90 mmol .sup.13C-MeTFA, 0.676 mmol
KCl and 7.70 mmol NH.sub.4IO.sub.3 were added to 8.0 mL of HTFA
with 3450 kPa of methane and heated for 1 h at 180.degree. C., only
0.14 mmol (15% of starting material) of .sup.13C-MeTFA was consumed
(FIG. 2.1). GC-MS data showed that the .sup.13MeTFA was transformed
to .sup.13CO.sub.2. No evidence of .sup.13CH.sub.2X.sub.2 or
.sup.13CHX.sub.3 intermediates was observed by .sup.1H NMR. In
contrast, 1.81 mmol of MeTFA were produced from CH.sub.4 during
this same time period. This result highlights the "protecting"
ability of the electron-withdrawing TFA moiety towards over
oxidation. A detailed kinetic comparison of the reactivity of
CH.sub.4 and MeTFA is not possible since the concentration of
CH.sub.4 under these conditions is not known.
[0103] Carbon dioxide (observed by GC-TCD) is formed during the
course of the reaction. To determine the source of carbon dioxide
(methane or HTFA) the functionalization of .sup.13CH.sub.4 was
carried out. Reactions charged with 240 kPa (0.652
mmol).sup.13CH.sub.4 converted .about.15% of the .sup.13CH.sub.4
with 91% selectivity for .sup.13CH.sub.3X (X.dbd.CO.sub.2CF.sub.3,
Cl) (eq 3). Products were confirmed through analysis of the
resulting liquid and headspace by .sup.1H NMR and .sup.13C NMR
spectroscopy (see FIG. 2.2) and GC-MS (see Supporting Information).
GC-MS of the products from the .sup.13C labeled methane reaction
demonstrated that <2% of the methane was over oxidized to
CO.sub.2 (presumably, the remaining CO.sub.2 originates from
decarboxylation of HTFA as this is the only other carbon source in
the reaction). Mass balance of the resultant mixture of methane,
MeTFA, CH.sub.3Cl, CH.sub.2Cl.sub.2 and CO.sub.2 accounted for
.about.99% of the initial methane (see Supporting Information).
##STR00003##
[0104] The influence of methane pressure on conversion efficiency
was probed. Although the iodate/chloride system is effective at
lower pressures (<3450 kPa), yields of MeTFA after 2 h are
higher at elevated pressures (.gtoreq.3450 kPa) of methane.
Analyzing reactions between 240 and 5520 kPa after 2 h of reaction
at 180.degree. C. revealed that increasing methane pressure
provides increased production of the methyl ester (FIG. 2.3).
Although conditions of the reaction make a rigorous kinetic
analysis difficult, the data in FIG. 2.3 are consistent with a
reaction that is first order in methane assuming that Henry's Law
is followed. At 6900 kPa after 2 h of reaction, the production of
MeTFA was observed to reach a maximum value of .about.0.5 M MeTFA
with 130:1 ratio of MeTFA:CH.sub.3Cl. For each reaction, sampling
of the reactor headspace and analysis by GC-TCD reveals negligible
or no CH.sub.3Cl.
[0105] The partial oxidation of methane can also be achieved over a
wide temperature range, between 100-235.degree. C. (FIG. 2.4).
Reactions at 235.degree. C. with 3450 kPa of methane, 0.676 mmol of
KCl, 7.70 mmol of NH.sub.4IO.sub.3 are rapid with .about.24%
conversion of methane to MeTFA in 20 min.
[0106] Both chloride and iodate were observed to play a crucial
role in the methane conversion (see Supporting Information). MeTFA
is not formed in substantial amounts in the absence of a chloride
source (<1% conversion for "background" reactions that use
iodate in the absence of chloride), and use of other halogens
(F.sup.-, Br.sup.- or I.sup.-) gives only background reactions.
[0107] Exclusion of iodate results in no reaction. The use of
KBrO.sub.3 gives only small amounts of MeTFA while a complex
mixture of intractable products was observed for reactions using
KClO.sub.3 as an oxidant. Methane conversions varied with the
choice of chloride and iodate sources (FIG. 2.5). Potassium
chloride was found to be the optimal source of chloride. Other
chloride sources, including metallic and non-metallic sources, were
found to successfully convert methane to methyl trifluoroacetate
(FIG. 2.5). Of the iodate sources tested, only iodic acid and
silver iodate showed poor activity. Ammonium iodate surpassed other
iodates by a factor of nearly two. .sup.1H NMR spectroscopy
indicated that the ammonium ion is not consumed during the course
of the methane functionalization reaction. The effect of the
potassium chloride concentration was examined (Table 1). Only 0.02
mmol of MeTFA formed without the addition of KCl due to the
background reaction. As the amount of KCl is increased, the yield
of MeTFA increases. High yields of MeTFA were determined for the
addition of 451 mmol, 676 mmol and 901 mmol of KCl. Also, the
amount of MeCl increases with increased amount of KCl.
TABLE-US-00001 TABLE 1 Impact of KCl concentration on methane
conversion to MeX. KCl MeTFA MeCl (.mu.mol) (mmol) (mmol) 0 0.02
Not observed 225 0.11 Not observed 451 1.26 0.03 676 1.75 0.06 901
2.00 0.06
Conditions: 7.7 mmol NH.sub.4IO.sub.3; 8.0 mL HTFA;
p.sub.CH4/Ne=3450 kPa; 180.degree. C.; 1 h; 600 rpm.
[0108] The results of acid screening are shown in Table 2.
Trifluoroacetic acid was observed to give the highest yields of the
methyl ester. In contrast to chemistry that was developed around
elemental iodine,.sup.61-64 only trace amounts of functionalized
products were observed in sulfuric acid when using
IO.sub.3.sup.-/Cl.sup.-. Electrophilic functionalization of alkanes
in acids weaker than H.sub.2SO.sub.4 and HTFA can be a challenge,
but the IO.sub.3.sup.-/Cl.sup.- system can be performed in aqueous
HTFA or even acetic acid. For example, reaction in acetic acid led
to the formation of 0.20 mmol of methyl acetate (MeOAc) after 2 h
at 180.degree. C. Furthermore, reactions using 6.5 mL of a 1:3 mol
% H.sub.2O:HTFA mixture containing 0.676 mmol KCl, 7.7 mmol
NH.sub.4IO.sub.3 and 3450 kPa (8.4 mmol) of methane heated at
180.degree. C. for 1 h resulted in the formation of 1.21 mmol
MeTFA, 0.03 mmol MeCl and 0.004 .mu.mol of MeOH.
[0109] Ethane was found to react with even greater conversion and
selectivity than methane (eq 4). Solutions of KCl (0.676 mmol) with
NH.sub.4IO.sub.3 (7.7 mmol) in 8.0 mL HTFA placed under 2070 kPa
C.sub.2H.sub.6(6.7 mmol) lead to the formation of 2.03 mmol of
mono-functionalized EtTFA (30% yield based on ethane) with a small
amount of 1,2-di-functionalized product (0.06 mmol) in 1 h at
180.degree. C. The resulting .sup.1H NMR spectrum is shown in FIG.
2.6. The selectivity for EtX (X=TFA, Cl) products was found to be
.about.97%. In an independent reaction, ethylene was converted in
.about.50% yield to ethylene glycol bistrifluoroacetate under the
catalytic conditions with no observed 1,1-bis-TFA product. Under
identical conditions in the absence of KCl only 1% of the ethane
was functionalized to EtTFA. The reaction of propane (830 kPa, 3.0
mmol) with 0.676 mmol KCl and 7.7 mmol NH.sub.4IO.sub.3 in HTFA at
180.degree. C. resulted in the production of 1-propyl (0.121 mmol),
2-propyl (0.202 mmol) and 1,2-propyl (0.236 mmol) trifluoroacetate
products as shown in eq 5 corresponding to 19% conversion based on
propane. The reaction is 58% selective for mono-functionalized
products that were formed in a nearly 1:2 ratio of terminal to
internal oxidation. The production of any terminal functionalized
propane is rare. For example, I(III)-mediated oxidation of hexane
has been reported to oxidize only the internal methylene
groups..sup.57,58
TABLE-US-00002 TABLE 2 Comparison of solvents for methane
conversion to MeX. Yield Entry Solvent Product (mmol) 1
CF.sub.3CO.sub.2H MeO.sub.2CCF.sub.3 0.42 2
CF.sub.3(CF.sub.2).sub.2CO.sub.2H
MeO.sub.2C(CF.sub.2).sub.2CF.sub.3 0.38 3 CH.sub.3CO.sub.2H
MeO.sub.2CCH.sub.3 0.20 4 H.sub.2SO.sub.4 MeOSO.sub.3H trace 5
H.sub.2O MeOH trace Conditions: 0.338 mmol [Cl.sup.-]; 2.26 mmol
NH.sub.4IO.sub.3; 2.0 mL solvent; p.sub.CH4/Ne = 5520 kPa;
180.degree. C.; 2 h; 600 rpm.
##STR00004##
[0110] Other iodine reagents proved feasible for alkane conversion
(Table 3). Species of interest include ICl, ICl.sub.3,
I(TFA).sub.3, IO.sup.+ and IO.sub.2.sup.+.
TABLE-US-00003 TABLE 3 Stoichiometric partial oxidation of methane
using various iodine sources. % Yield.sup.a Entry Species Additive
MeTFA 1 I.sub.2 -- -- 2 I.sub.2 KCl -- 3 I.sub.2 NH.sub.4IO.sub.3 2
4 ICl -- -- 5 ICl.sub.3 -- 5 (43).sup.b 6 I(TFA).sub.3 -- 7 7
I(TFA).sub.3 KCl 43 8 I.sub.2O.sub.4 -- 2 (15).sup.c 9
I.sub.2O.sub.4 KCl 30 (17).sup.c 10 I.sub.2O.sub.5 -- 1 (2).sup.b
11 I.sub.2O.sub.5 KCl 4.1 12 (IO.sub.2).sub.2S.sub.2O.sub.7 --
<1 13 (IO.sub.2).sub.2S.sub.2O.sub.7 KCl 48 14
(IO).sub.2SO.sub.4 -- 5.3 15 (IO).sub.2SO.sub.4 KCl 31 .sup.a%
yield based on moles iodine reagent. .sup.b% yield MeCl given in
parenthesis. .sup.c% yield Mel given in parenthesis. Conditions:
0.4 mmol iodine reagent; 0.1 mmol KCl if added; p.sub.CH4/Ne = 3450
kPa; 180.degree. C.; 800 rpm; 1 h.
[0111] The reaction of CH.sub.4 in HTFA at 180.degree. C. with 0.4
mmol I(TFA).sub.3, I.sub.2O.sub.4,.sup.69I.sub.2O.sub.5,.sup.41
[(IO.sub.2).sub.2S.sub.2O.sub.7].sup.70 or
[(IO).sub.2SO.sub.4].sup.71 in the absence of chloride results in
minimal conversion (.ltoreq.7% yield) to MeTFA (Table 3). But, for
all these iodine-based reagents except I.sub.2O.sub.5, the addition
of 0.1 mmol KCl results in a dramatic increase in the yield of
MeTFA (Table 3). Similar to the iodate/chloride reactions, KCl is
effective in a sub-stoichiometric quantity. The highest percent
yield of MeTFA was achieved using [(IO.sub.2).sub.2S.sub.2O.sub.7],
which gave a nearly 50% yield. I(TFA).sub.3 with KCl also gave a
high yield (43%) of MeTFA, and the combined yield of MeTFA and MeI
(47%) was high for I.sub.2O.sub.4 and KCl.
Summary
[0112] Alkanes are converted to mono-functionalized esters in good
yields with the use of simple chloride salts (in catalytic amounts)
and with iodate as the sole oxidant in acidic media such as
trifluoroacetic acid, acetic acid or even aqueous trifluoroacetic
acid. The system operates over a large range of pressures (240-6900
kPa) and temperatures (100-235.degree. C.) and exhibits excellent
selectivity for monofunctionalized products. Conversions of methane
to MeTFA>20% have been achieved, and conversion of ethane is
even more efficient with .about.30% yield of EtTFA. Although
propane conversion is less efficient, the ability to form
mono-functionalized products selectively with some terminal
activation is notable. These values for alkane conversion meet many
of the established benchmarks for efficient alkane
functionalization..sup.72 A potential benefit of the
iodate/chloride system is that iodine (the byproduct of
KCl/IO.sub.3.sup.- oxidation reactions) can be reoxidized to iodate
in basic aqueous solution with molecular oxygen. Also, iodates have
been generated from iodide sources electrochemically..sup.73 The
distinct reactivity imparted by chloride (compared with I.sub.2,
IO.sub.3.sup.-, I(TFA).sub.3, etc. with no chloride or these
species with other halides) is unique and without precedent,
resulting in substantial increases in efficiency for production of
mono-functionalized alkanes. The exact role of chloride is unknown
at this point and will be the subject of future studies, but the
chloride enhancement is observed for several iodine-based reagents
(Table 3). Given the differences between classic oxychlorination
and the iodate/chloride process (e.g., reaction temperature,
product selectivity and efficacy for ethane and propane), it seems
unlikely that the formation of chlorine radical is the key role of
chloride. It is possible that chloride bonds with the active
iodine-based reagent to provide an electronic modulation for the
C--H bond breaking step and/or the C--O bond-forming step. Iodosyl
chloride and iodyl chloride have been observed
experimentally..sup.74 The presence of iodine-oxo bonds suggests a
possible similarity to C--H bond breaking by metal oxo or imide
complexes..sup.23,75-77 But, the enhancement observed when adding
chloride to the I(TFA).sub.3 reaction suggests that the chloride
enhancement is not limited to iodine oxides. Although challenges
remain, the reported iodate/chloride process functionalizes alkanes
rapidly (in 20 min under some conditions), with good conversion and
selectivity, under a broad range of temperatures and pressures and
with an oxidant that in theory can be thermally recycled using
dioxygen.
Experimental Section
General Considerations:
[0113] Unless stated otherwise, all reactions were prepared in air.
Trifluoroacetic acid (HTFA), trifluoroacetic anhydride (TFAA),
methyl trifluoroacetate ester (MeTFA), acetic acid (HOAc), iodic
acid, formic acid, sulfuric acid, iodine trichloride, iodine
monocloride, I.sub.2O.sub.5, iodomethane, chloromethane, iodine as
well as all iodates and chlorides were purchased from VWR and used
as received. Methane/neon (9:1 mol), ethane and propane were
purchased from GTS Welco. Trifluoroacetic acid-d.sub.1 (DTFA),
.sup.13C-methane and .sup.13C-methanol were purchased from
Cambridge Isotopes and used as received. Iodyl pyrosulfate,.sup.70
iodosyl sulfate,.sup.71 diiodine tetraoxide.sup.69 and
tris-(trifluoroaceto) iodine.sup.80 were prepared according to
literature procedures. H and .sup.13C NMR spectra were recorded on
either a Bruker 600, 500 or 300 MHz NMR spectrometer. NMR spectra
taken in HTFA or DTFA included a capillary tube filled with
C.sub.6D.sub.6 that was used as an internal lock reference.
Chemical shifts in HTFA are reported relative to standards of HOAc
(.sup.1H NMR d=2.04) or dichloromethane (DCM; .sup.1H NMR d=5.03).
This shift was chosen so that the products would remain at the same
chemical shifts when using different standards. At least one
reaction was spiked with the alternative internal standard to
ensure the integrity of the standards and to ensure that the
standard was not a product of the reaction (i.e., DCM was used to
determine if HOAc was a product of the reaction). GC-MS were
obtained on a Shimadzu GC-2010 equipped with a Restek RT.RTM.-Qbond
30 m.times.8 mm fused silica PLOT column. GC-TCD were obtained with
a Shimadzu GC-2014 equipped with a 500 mL injection loop in which
the sample passed through 3 columns in series (Hayesep.RTM. T
80/100 mesh 0.5 m.times.2.0 mm, Supelco.RTM. 60/80 Mesh 5 .ANG.
molecular sieve 2.0 m.times.2.1 mm and Hayesep.RTM. Q 80/100 mesh
1.5 m.times.2.0 mm). UV-Vis spectra were recorded on Varian Carey
300 Bio UV-Vis spectrophotometer. Reactions of
Cl.sup.-/IO.sub.3.sup.- in acid with alkanes:
[0114] Reactions were carried out in two separate types of
high-pressure reactors. Reactions consisting of a solvent volume of
>2.0 mL used in-house built high-pressure reactors constructed
primarily of stainless steel Swagelok.RTM. parts. The reactors were
equipped with Teflon liners. With liners inserted, the average
reactor volume is 16.1 mL. Heating was accomplished through
inductive heat transfer from tight fitting custom aluminum blocks.
Screening of reagents and conditions were typically carried out in
a custom built Asynt Ltd. high-pressure carousel. The carousel is
constructed of Hastelloy.RTM.C-276 and contains 9.times.7 mL
reaction chambers. Reactions were carried out in glass liners
within the reaction chambers. Reaction temperatures were maintained
through direct heat from a RTC-basic hotplate equipped with
temperature control. The carousel was insulated by wrapping in
fiberglass fabric. The amounts reported for products formed for all
functionalization reactions are the average of at least 3
independent reactions.
Methane Functionalization:
[0115] In a typical reaction with methane, a stir bar, 0.676 mmol
KCl, 7.7 mmol NH.sub.4(IO.sub.3) and 8.0 mL of HTFA were loaded
into the 16.1 mL VCO reactor that contained a tight fitting Teflon
liner. After the reactor was sealed and weighed, it was purged
three times with CH.sub.4/Ne and finally charged with 3450 kPa of
90 mol % CH.sub.4/10 mol % Ne (8.4 mmol CH.sub.4). The reactor was
weighed to quantify the amount of gas added, then subsequently
heated and stirred (800 rpm) for 1 h. The reactor was removed from
the heating block, placed in front of a fan and cooled to room temp
for 30 min. The reactor was reweighed to ensure no leakage occurred
over the course of the reaction. The resultant gas was collected in
a gas bag and analyzed by GC-TCD. A standard of 30 mL of HOAc
and/or 30 mL of DCM was added to the reaction liquid. The mixture
was stirred, then a sample was removed for centrifugation. The
products were analyzed by .sup.1H NMR, .sup.13C NMR and GC-MS. 1.75
mmol MeTFA and 0.06 mmol of MeCl were formed. .sup.1H NMR (d)=3.85
(3H, H.sub.3C--O.sub.2CCF.sub.3, s); .sup.13C NMR (d)=50.8
(H.sub.3C--O.sub.2CCF.sub.3, q, .sup.4J.sub.C-F=17 Hz), carbonyl
carbon and CF.sub.3 carbon overlap with HTFA resonances.
[0116] In a typical reaction with methane in the carousel, a stir
bar, 0.338 mmol KCl, 2.26 mmol NH.sub.4(IO.sub.3) and 2.0 mL of
HTFA were loaded into individual glass vials. The vials were
transferred into the reactor. After the reactor was sealed, it was
purged 3 times with CH.sub.4/Ne and finally charged with 5515 kPa
of 90 mol % CH.sub.4/10 mol % Ne. The reactor was subsequently
heated and stirred (600 rpm) for 2 h. The reactor was removed from
the heating block, placed in front of a fan and cooled to room temp
for 30 min. The resultant gas was collected in a calibrated gas
burette to obtain the final amount of gas contained in the reactor.
This gas was analyzed by GC-TCD. A standard of 10 mL of HOAc and/or
10 mL of DCM was added to the reaction liquid. The mixture was
stirred, then a sample was removed for centrifugation. The products
were analyzed by .sup.1H NMR spectroscopy, .sup.13C NMR
spectroscopy and GC-MS. The amount of MeTFA formed (minus
background; 0.04 mmol) was determined to be 0.86 mmol MeTFA.
.sup.13C-Methane Functionalization
[0117] Four carousel chambers were individually charged with a stir
bar, 0.338 mmol KCl, 2.26 mmol KIO.sub.3 and 2.0 mL of HTFA. After
the reactor was sealed, it was purged 2 times with argon, once with
.sup.13CH.sub.4 and finally charged with 240 kPa of .sup.13CH.sub.4
(0.652 mmol). The reaction was heated for 2 h and stirred at 600
rpm. The reactor was cooled to room temperature over 30 min. The
resultant gas was collected in a gas bag. A portion was evaluated
by GC-MS to determine the amount of .sup.13CO.sub.2 produced (0.011
mmol), and the remaining was vented directly into the sample loop
of the GC-TCD and final gas concentrations were determined through
independently determined calibration curves. A standard of 10 mL of
HOAc was added to the reaction liquid. The mixture was stirred, and
a sample was removed for centrifugation. The products were analyzed
by .sup.1H NMR spectroscopy, .sup.13C NMR spectroscopy and GC-MS.
From the reaction 80 mmol of .sup.13CH.sub.3TFA, 6 mmol of
.sup.13CH.sub.3Cl and 5 mmol of .sup.13CH.sub.2Cl.sub.2 were
formed. .sup.1H NMR (d)=3.85 (3H, .sup.13CH.sub.3TFA, d,
.sup.1J.sub.C-H=151 Hz), 2.78 (3H, .sup.13CH.sub.3Cl, d,
.sup.1J.sub.C-H=150 Hz), 5.03 (2H, .sup.13CH.sub.2Cl.sub.2, d,
.sup.1J.sub.C-H=178 Hz). .sup.13C NMR (d)=50.8
(.sup.13CH.sub.3TFA), 25.1 (.sup.13CH.sub.3Cl), 53.0
(.sup.13CH.sub.2Cl.sub.2).
Retention of MeTFA:
[0118] In a vial, 1.0 g of .sup.13CH.sub.3OH was added slowly to an
equimolar amount of TFAA during continuous stirring to produce
.sup.13CH.sub.3-TFA and HTFA. A known volume was sampled and
diluted into HTFA. The sample was spiked with HOAc and .sup.1H NMR
was used to determine the concentration of .sup.13CH.sub.3-TFA. A
reaction was then set up analogous to the methane functionalization
reaction in the 16.1 mL VCO reactor described above (0.667 mmol
KCl; 7.7 mmol NH.sub.4IO.sub.3; 8.0 mL HTFA). This mixture was then
spiked with 0.9 mmol of the .sup.13CH.sub.3-TFA stock solution. The
reactor was sealed, purged with CH.sub.4 3.times. times and
pressurized to 3450 kPa of CH.sub.4/Ne (9:1). The reaction was
heated (180.degree. C.) and stirred (800 rpm) for 1 h, and cooled
to room temperature. The over pressure was vented into a gas bag
and this gas was analyzed by GC-MS. 30 mL of HOAc was added as a
standard and the reaction was stirred and sampled as detailed
above. .sup.1H NMR of the liquid revealed that .about.85% of the
.sup.13CH.sub.3-TFA was retained and that 1.7 mmol MeTFA was formed
during the reaction. The presence of methane was found to not be
crucial to the reaction as a similar reaction run without the
overpressure of methane resulted in the same amount of
.sup.13CH.sub.3-TFA retained.
Functionalization Reactions of CH.sub.4 and C.sub.2H.sub.6 with
Added O.sub.2:
[0119] In a typical reaction with methane, a stir bar, 0.676 mmol
KCl, 7.7 mmol NH.sub.4(IO.sub.3) and 8.0 mL of HTFA were loaded
into the 16.1 mL VCO reactor that contained a tight fitting Teflon
liner. After the reactor was sealed and weighed, it was purged
three times with CH.sub.4/Ne. The reaction was pressurized to 340
kPa O.sub.2 (0.8 mmol O.sub.2) and finally pressurized to 3450 kPa
of 90 mol % CH.sub.4/10 mol % Ne (7.6 mmol CH.sub.4). The reactor
was subsequently heated and stirred (800 rpm) for 1 h. The reactor
was removed from the heating block, placed in front of a fan and
cooled to room temp for 30 min. The resultant gas was collected in
a gas bag and analyzed by GC-TCD. A standard of 30 mL of HOAc
and/or 30 mL of DCM was added to the reaction liquid. The mixture
was stirred, then a sample was removed for centrifugation. The
products were analyzed by .sup.1H NMR, .sup.13C NMR and GC-MS. 1.73
mmol MeTFA and 0.06 mmol of MeCl were formed. The reaction with
ethane and oxygen were charged first with 255 kPa O.sub.2 then
filled to a final pressure of 2070 kPa with ethane. The reaction
was then carried out as described above.
Methane Functionalization with Various Sources of Iodine:
[0120] Reactions in this case were carried out with various sources
of iodine in different oxidation states. These reactions were
carried out with and without added potassium chloride. The
reactions using ICl and ICl.sub.3 were prepared inside a glovebox.
A typical reaction is as follows: A stir bar, 0.4 mmol
I.sub.2O.sub.4, 0.1 mmol KCl and 6.0 mL of HTFA were loaded into
the 16.1 mL VCO reactor which contained a tight fitting Teflon
liner. The reactors were sealed and weighed. The reactor was
attached to a high-pressure line and flushed 3.times. with
CH.sub.4/Ne (9:1). The reactor was then charged to 3450 kPa (8.4
mmol CH.sub.4) with the same gas mixture and weighed again to
obtain the amount of gas added. The reactor was weighed and
subsequently heated and stirred (800 rpm) for 1 h. The reactor was
removed from the heating block, placed in front of a fan and cooled
to room temp for 30 min. The resultant gas was collected in a gas
bag and analyzed by GC-TCD. A standard of 30 mL of HOAc and/or 30
mL of DCM was added to the reaction liquid. The mixture was
stirred, then a sample was removed for centrifugation. The products
were analyzed by .sup.1H NMR, GC-MS. 0.238 mmol MeTFA and 0.137
mmol of MeCl were formed. Yields for these reactions are given in
terms of moles of iodine reagent. For this reaction the yield for
MeTFA is given as 30% and for MeCl as 17%.
Methane Functionalization with SO.sub.2Cl.sub.2 or
N-Chlorosuccinimide:
[0121] The reactions were performed according to the methane
functionalization procedure above, except SO.sub.2Cl.sub.2 or
N-chlorosuccinimide (NCS) was used instead of KCl. For the
reactions, 0.676 mmol NCS or 0.338 mmol SO.sub.2Cl.sub.2 were
combined with 7.7 mmol NH.sub.4IO.sub.3 in 8 mL of HTFA and
pressurized with 3450 kPa CH.sub.4. The reactors were heated at
180.degree. C. for 1 h, then cooled and analyzed.
Ethane Functionalization:
[0122] In a typical reaction with ethane a stir bar, 0.676 mmol
KCl, 7.7 mmol NH.sub.4IO.sub.3 and 8.0 mL of HTFA were loaded into
the reactor. After the reactor was sealed, it was purged 3 times
with ethane and finally charged with 2070 kPa of ethane (6.7 mmol
ethane). The reactor was weighed and subsequently heated and
stirred (800 rpm) for 1 h. The reactor was removed from the heating
block and cooled to room temp for 30 min. The resultant gas was
collected in a gas bag and analyzed by GC-TCD. A standard of 30 mL
of HOAc or DCM was added to the reaction liquid. The mixture was
stirred, then a sample was removed for centrifugation. The products
were analyzed by .sup.1H NMR and GC-MS. 2.03 mmol EtTFA; 0.13 mmol
EtCl and 0.06 mmol 1,2-bis(trifluoroacetyl)ethane (glycol) were
formed in the reaction. .sup.1H NMR
(d)=1,2-bis(trifluoroacetyl)ethane -4.49 (4H, 4.25,
H.sub.2C--O.sub.2CCF.sub.3). ethyl trifluoroacetate: 4.27 (2H,
CH.sub.3H.sub.2C--O.sub.2CCF.sub.3, q, .sup.3J.sub.H-H=7 Hz), 1.18
(3H, CH.sub.3H.sub.2C--O.sub.2CCF.sub.3, t, .sup.3J.sub.H-H=7 Hz).
ethyl chloride -4.19 (CH.sub.3CH.sub.2Cl, br), 2.08
(CH.sub.3CH.sub.2Cl, overlap with HOAc standard).
Ethylene Functionalization:
[0123] In a typical reaction with ethylene a stir bar, 0.676 mmol
KCl, 7.7 mmol NH.sub.4IO.sub.3 and 8.0 mL of HTFA were loaded into
the reactor. After the reactor was sealed, it was purged three
times with ethylene and finally charged with 1379 kPa ethylene (4.3
mmol ethylene). The reactor was weighed and subsequently heated and
stirred (800 rpm) for 1 h. The reactor was removed from the heating
block and cooled to room temp for 30 min. The resultant gas was
collected in a gas bag and analyzed by GC-TCD. A standard of 30 mL
of DCM was added to the reaction liquid. The mixture was stirred,
then a sample was removed for centrifugation. The products were
analyzed by .sup.1H NMR spectroscopy and GC-MS. 2.20 mmol of
1,2-bis(trifluoroacetyl)ethane was formed. .sup.1H NMR (d)=ethylene
glycol: 4.49 (4H, H.sub.2C--O.sub.2CCF.sub.3). Reactions without
added chloride also lead to similar reactivity. Under the same
conditions these reactions yielded 11% glycol and 21% of what is
tentatively assigned as 1-trifluoroacetyl-2-iodoethane. .sup.1H NMR
(d)=1-trifluoroacetyl-2-iodoethane: 4.44 (2H,
H.sub.2C--O.sub.2CCF.sub.3, t, .sup.3J.sub.H-H=6.8 Hz); 3.17 (2H,
H.sub.2C--I, t, .sup.3J.sub.H-H=6.8 Hz)
Propane Functionalization:
[0124] In a typical reaction with propane a stir bar, 0.676 mmol
KCl, 7.7 mmol NH.sub.4IO.sub.3 and 8.0 mL of HTFA were loaded into
the reactor. After the reactor was sealed, it was purged 3 times
with propane and finally charged with 830 kPa propane (3.0 mmol
propane). The reactor was weighed and subsequently heated and
stirred (800 rpm) for 2 h. The reactor was removed from the heating
block, cooled to room temp. The resultant gas was collected in a
gas bag and analyzed by GC-TCD. A standard of 30 mL of HOAc was
added to the reaction liquid. The mixture was stirred, after which
a sample was removed for centrifugation. The products were analyzed
identified by .sup.1H NMR and GC-MS. 121 mmol of
1-trifluoroacetopropane, 404 mmol of 2-trifluoroacetopropane and
236 mmol of bis(1,2-trifluoroaceto)propane were formed in the
reaction. .sup.1H NMR (d)=1-trifluoroacetopropane 4.17 (2H,
H.sub.2C--O.sub.2CCF.sub.3, t, .sup.3J.sub.H-H=7 Hz), 1.59 (2H,
CH.sub.2CH.sub.3, m) 0.79 (3H, CH.sub.3, t, .sup.3J.sub.H-H=7 Hz);
2-trifluoroacetopropane 4.17 (1H, HC--O.sub.2CCF.sub.3, h,
.sup.3J.sub.H-H=6 Hz), 1.18 (6H, CH.sub.3, d, .sup.3J.sub.H-H=6
Hz); bis-(1,2-trifluoroaceto)propane. 5.27 (1H,
HC--O.sub.2CCF.sub.3, m), 4.38 (1H, H.sub.2C--O.sub.2CCF.sub.3, dd,
.sup.2J.sub.H-H=12 Hz, .sup.3J.sub.H-H=3 Hz), 4.27 (1H,
H.sub.2C--O.sub.2CCF.sub.3, dd, .sup.2J.sub.H-H=12 Hz,
.sup.3J.sub.H-H=7 Hz), 1.26 (3H, CH.sub.3, d, .sup.3J.sub.H-H=7
Hz).
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[0205] It should be noted that ratios, concentrations, amounts, and
other numerical data may be expressed herein in a range format. It
is to be understood that such a range format is used for
convenience and brevity, and thus, should be interpreted in a
flexible manner to include not only the numerical values explicitly
recited as the limits of the range, but also to include all the
individual numerical values or sub-ranges encompassed within that
range as if each numerical value and sub-range is explicitly
recited. To illustrate, a concentration range of "about 0.1% to
about 5%" should be interpreted to include not only the explicitly
recited concentration of about 0.1 wt % to about 5 wt %, but also
include individual concentrations (e.g., 1%, 2%, 3%, and 4%) and
the sub-ranges (e.g., 0.5%, 1.1%, 2.2%, 3.3%, and 4.4%) within the
indicated range. In an embodiment, the term "about" can include
traditional rounding according to significant figures of the
numerical value. In addition, the phrase "about `x` to `y`"
includes "about `x` to about `y`".
[0206] It should be emphasized that the above-described embodiments
of the present disclosure are merely possible examples of
implementations, and are set forth only for a clear understanding
of the principles of the disclosure. Many variations and
modifications may be made to the above-described embodiments of the
disclosure without departing substantially from the spirit and
principles of the disclosure. All such modifications and variations
are intended to be included herein within the scope of this
disclosure.
* * * * *
References