U.S. patent application number 09/768604 was filed with the patent office on 2002-03-14 for organic base hydrogenofluorosulphonates, their use in releasing organic bases from their fluorohydrate, method of preparation thereof, compound containing them.
Invention is credited to Morel, Marcel, Saint-Jalmes, Laurent.
Application Number | 20020031466 09/768604 |
Document ID | / |
Family ID | 9491817 |
Filed Date | 2002-03-14 |
United States Patent
Application |
20020031466 |
Kind Code |
A1 |
Saint-Jalmes, Laurent ; et
al. |
March 14, 2002 |
Organic base hydrogenofluorosulphonates, their use in releasing
organic bases from their fluorohydrate, method of preparation
thereof, compound containing them
Abstract
The invention features the use of fluorosulphonates to release
the organic bases from their fluorohydrate. This use is
characterized in that a hydrogenofluorosulphonate of an organic
base is formed and in that the hydrofluoric acid which is
associated with the said base or with one of its precursors is
separated therefrom. The invention is useful in organic synthesis
applications.
Inventors: |
Saint-Jalmes, Laurent;
(Meyzieu, FR) ; Morel, Marcel; (Brignais,
FR) |
Correspondence
Address: |
Norman H. Stepno
BURNS, DOANE, SWECKER & MATHIS, L.L.P.
P.O. Box 1404
Alexandria
VA
22313-1404
US
|
Family ID: |
9491817 |
Appl. No.: |
09/768604 |
Filed: |
January 25, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09768604 |
Jan 25, 2001 |
|
|
|
09171990 |
Jan 19, 1999 |
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Current U.S.
Class: |
423/467 |
Current CPC
Class: |
C07C 209/62 20130101;
Y02P 20/582 20151101; C01B 7/195 20130101; C07C 209/84 20130101;
C01B 7/191 20130101 |
Class at
Publication: |
423/467 |
International
Class: |
C01B 017/45; C01B
017/46 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 30, 1996 |
FR |
96/05573 |
Claims
1. Use of the hydrogen fluorosulphonate form of an organic base to
separate from it the hydrofluoric acid which is combined with the
said base or which is combined with one of its precursors.
2. Use according to claim 1, characterized in that the said base is
a nitrogen base.
3. Use according to claims 1 and 2, characterized in that the said
base is chosen from amines (including cyclic amines) and imines
(including aromatic heterocycles).
4. Use according to claims 1 to 3, characterized in that the said
base is chosen from phosphines (including cyclic phosphines) and
aromatic heterocycles containing a phosphorus as hetero atom.
5. Use according to claims 1 to 4, characterized in that the said
base is chosen from those whose pKa in combined form is not more
than 8, advantageously not more than 7.
6. Use according to claims 1 to 5, characterized in that the said
base is chosen from those capable of forming complexes with
hydrofluoric acid in which the ratio between the hydrofluoric acid
and the basic functions is at least equal to 5.
7. Use according to claims 1 to 6, characterized in that the said
base is combined with hydrofluoric acid in the form of a
precursor.
8. Use according to claims 1 to 7, characterized in that the said
precursor is a precursor which releases the said base by consuming
a molecule of water.
9. Use according to claims 1 to 8, characterized in that the said
precursor is a function which releases carbon dioxide.
10. Use according to claims 1 to 9, characterized in that the said
base is an amine (including an aniline) and the said precursor is a
function which releases carbon dioxide.
11. Use according to claims 1 to 10, characterized in that the said
base is an amine and the precursor function is an isocyanate
function or a function derived therefrom (carbamoyl urea [halide,
usually fluoride] or carbamate).
12. Use according to claims 1 to 11, characterized in that the said
hydrogen fluorosulphonate is formed in situ.
13. Process for treating a composition containing an organic base
or its precursor and anhydrous hydrofluoric acid, characterized in
that it includes a step a) in which the hydrogen fluorosulphonate
of the said organic base is formed.
14. Process according to claim 13, characterized in that it
includes, after step a), a step b) in which the hydrofluoric acid
is recovered from the composition thus modified.
15. Process according to claims 13 and 14, characterized in that
the fluorosulphonic acid is manufactured in situ by the action of
sulphuric acid or sulphur trioxide (SO.sub.3) on the said
composition.
16. Process according to claims 14 and 15, characterized in that
the fluorosulphonic acid is manufactured in situ by the action of
sulphuric acid on the hydrofluoric acid from the composition in the
presence of a dehydrating agent.
17. Process according to claim 16, characterized in that the said
dehydrating agent is the precursor of the said base.
18. Process according to claim 17, characterized in that the said
organic base is an amine and the said precursor of the said base is
an isocyanate function or a function which is derived therefrom
(for example carbamoyl urea [halide, usually fluoride] or
carbamate).
19. Process according to claim 18, characterized in that the
reaction is carried out at a temperature of between 0.degree. C.
and 100.degree. C.
20. Process according to claim 19, characterized in that the said
recovery of the hydrofluoric acid in step b) is a distillation.
21. Process according to claims 1 to 20, characterized in that the
said recovery of the hydrofluoric acid in step b) is an
extraction.
22. Hydrogen fluorosulphonate of an organic base, which is useful
as a synthetic intermediate, characterized in that the said organic
base contains at least one fluorophoric atom chosen from
sp.sup.3-hybridized carbons and chalcogens from a row at least
equal to that of sulphur.
23. Hydrogen fluorosulphonate according to claim-22, characterized
in that the said organic base contains at least one fluorophoric
carbon or sulphur.
24. Hydrogen fluorosulphonate according to claims 22 and 23,
characterized in that the said organic base contains at least one
sp.sup.3-hybridized carbon or an SF.sub.5.
25. Hydrogen fluorosulphonate according to claims 22 to 24,
characterized in that the said organic base contains, as basic
function, a nitrogen or a trivalent phosphorus.
26. Composition containing both hydrofluoric acid and a hydrogen
sulphonate according to claims 22 to 25, characterized in that the
molar ratio between the hydrofluoric acid and the basic functions
of the said organic base (HF/basic functions of the said organic
base) is at least equal to 2, advantageously equal to 3, preferably
equal to 4.
27. Composition according to claim 26, characterized in that the
water content in the said composition is such that the number of
molecules of water in the composition is not more than half
(advantageously a quarter, preferably a tenth) of the number of
basic functions present in the composition.
28. Composition according to claims 26 and 27, characterized in
that the composition also contains sulphuric acid.
Description
[0001] The present invention relates to the use of
fluorosulphonates to release organic bases from their
hydrofluoride, to hydrogen fluorosulphonates of an organic base, to
processes for the preparation of fluorosulphonate(s) and to
compositions of organic base fluorosulphonate(s) and of
hydrofluoric acid. The invention relates more particularly to a
technique for separating hydrofluoric acid from organic bases
capable of forming combinations, usually constituting defined
compounds, with several, at least three, molecules of unitary
hydrofluoric acid (i.e. HF).
[0002] The process according to the present invention is
particularly suitable for bases which constitute, with hydrofluoric
acid, combinations containing more than two, advantageously three,
hydrofluoric acid units.
[0003] It is well known to those skilled in the art that organic
bases form, with hydrofluoric acid, complexes containing at least
three hydrofluoric acid units. Generally, the weaker and softer the
bases, the greater the number of hydrofluoric acid units per basic
function.
[0004] Now, on account of their specific properties, fluoro
compounds are in ever-increasing demand and used in applications
such as agriculture and health.
[0005] Fluoro derivatives are often difficult to synthesize and
often involve exchanges of various substituents with fluorine. Now,
the reagent most commonly used and the cheapest for carrying out
the exchange is undeniably hydrofluoric acid.
[0006] In addition, this acid is increasingly being used as a
reaction medium. Certain precursors of organic bases present
problems of stability, thus, carbamoyl fluorides show thermal
instability which leads to the formation of isocyanate or to the
formation of fluorophosgene (Hoechst, EP 639,556) which is very
difficult to handle on account of its toxicity. Moreover,
fluorophosgene leads to the loss of two fluorine atoms.
[0007] Accordingly, one of the aims of the present invention is to
provide a form of organic bases whose use allows appreciable
recovery of the hydrofluoric acid.
[0008] Another aim of the present invention is to provide a form of
the above type whose use allows the hydrolysis of carbamoyl
fluorides without releasing phosgenes and in particular
fluorophosgenes.
[0009] Another aim of the present invention is to provide a process
for preparing a form of the above type.
[0010] Another aim of the present invention is to provide a process
for preparing a form of the above type which allows the release of
the base from carbamoyl.
[0011] Another aim of the present invention is to provide a
composition containing the said organic base and at least two
equivalents of hydrofluoric acid per basic function, from which
composition recovery of the hydrofluoric acid is easy.
[0012] These aims and others which will emerge later are achieved
by means of using the hydrogen fluorosulphonate form of an organic
base in order to separate it from the hydrofluoric acid which is
combined with the said base or which is combined with one of its
precursors.
[0013] Thus, in the course of the study which led to the present
invention, it has been shown that fluorosulphonic acid (HFSO.sub.3)
is capable of displacing complexes between organic bases and
hydrofluoric acid, thus allowing the hydrofluoric acid to be
recovered.
[0014] The present invention is especially of interest for certain
bases, in particular phosphorus bases and especially nitrogen
bases.
[0015] Thus, when the said base is a nitrogen base, it is
advantageously chosen from amines (including cyclic amines) and
imines (including aromatic heterocycles).
[0016] When the said base is a phosphorus base, it is
advantageously chosen from phosphines (including cyclic
phosphines), and aromatic heterocycles containing a phosphorus as
hetero atom.
[0017] The greater the capacity of the said organic base to combine
with hydrofluoric acid and the greater the number of hydrofluoric
acid units-with which it can combine, the greater the advantage of
the present invention.
[0018] Thus, it is advantageous for the said organic base to be
chosen from those whose pKa in combined form is not more than 8,
advantageously not more than 7.
[0019] The said base is chosen from those capable of forming
complexes with hydrofluoric acid in which the ratio between the
hydrofluoric acid and the basic function (or at least one of the
basic functions when the molecule treated contains several basic
functions) is at least equal to 5.
[0020] As has been outlined above, the said base is combined with
hydrofluoric acid in the form of one of its precursors.
[0021] According to one particularly advantageous embodiment of the
present invention, the said precursor is a precursor which releases
the said base by consuming a molecule of water. This characteristic
has an advantage during the in-situ preparation of the
fluorosulphonate anion, as will be seen later.
[0022] According to an advantageous variant of the present
invention, in the said precursor, the function which-will be
converted into a basic function is a function which releases a gas
such as, for example, carbon dioxide.
[0023] When the said base is an amine (including an aniline), a
good example of a function which releases a gas (carbon dioxide)
can be found in carbamic acid derivatives, such as urea, carbamoyl
[often in the form of halide, usually fluoride] or carbamate
functions. These functions are derived from isocyanate
functions.
[0024] Given its cost, its relative instability and its
corrosiveness, it is advantageous for the said hydrogen
fluorosulphonate to be formed in situ.
[0025] Accordingly, one of the aims of the present invention is to
provide a process which makes it possible to release a base from
one of its complexes with-hydrofluoric acid.
[0026] This aim and others which will become apparent later are
achieved by means of a process which includes a step a) in which
the hydrogen fluorosulphonate of the said organic base is
formed.
[0027] Advantageously, this process includes, after step a), a step
b) in which the hydrofluoric acid is recovered from the composition
thus modified.
[0028] It is possible to form the hydrogen fluorosulphonate by a
simple action of fluorosulphonic acid on the complex between the
hydrofluoric acid and the said organic base. This is undoubtedly a
satisfactory route when an inexpensive source of such an acid is
available on site.
[0029] However, it is advantageous, and this is another aim of the
present invention, to be able to prepare fluorosulphonate in situ,
in particular from a composition containing hydrofluoric acid,
optionally combined with an organic base.
[0030] Thus, in the course of the study which led to the present
invention, it has been shown that fluorosulphonic acid can readily
be manufactured in situ by the action of sulphuric acid or sulphur
trioxide (sulphuric anhydride or SO.sub.3) on more or less
anhydrous organic compositions containing hydrofluoric acid.
[0031] When the said composition is wet and/or contains no
dehydrating agent, it is then advisable to use sulphur trioxide,
SO.sub.3, in its native form or in the form of oleum.
[0032] If the said composition contains a dehydrating agent, it may
then be advantageous to use sulphuric acid, optionally containing a
small amount of water (sulphuric acid at a concentration at least
equal to 80%, advantageously to 90%, often to 95). Thus, in this
embodiment of the present invention, the fluorosulphonic acid is
manufactured in situ by the action of sulphuric acid on the
hydrofluoric acid from the composition in the presence of a
dehydrating agent.
[0033] Advantageously, the said dehydrating agent is a precursor of
the said base.
[0034] The said organic base is an amine and the said precursor of
the said base is an isocyanate function or a function which is
derived therefrom (for example carbamoyl urea [halide, usually
fluoride] or carbamate).
[0035] The reaction for the synthesis of the fluorosulphonic anion
is carried out at a temperature of between 0.degree. C. and
100.degree. C., distillation temperature of HF, advantageously
between 0.degree. C. and 50.degree. C., preferably between
0.degree. C. and 20.degree. C.
[0036] Although it is possible to envisage carrying out the said
recovery of the hydrofluoric acid in a different manner, and in
particular by liquid extraction, it is generally preferred for step
b) of hydrofluoric acid recovery to be a distillation.
[0037] The present process is particularly advantageous for
recycling the base acid reagents which are increasingly being
developed, in particular reagents consisting of aromatic
heterocycle(s), and of hydrofluoric acid, for which family of
reagents the compound [pyridine, 10HF] can be considered a prime
example.
[0038] It can also be especially advantageous for the release of
those so-called organic bases (particularly advantageous also for
the corresponding fluorosulphonates) which contain at least one
fluorophoric carbon or sulphur.
[0039] Advantageously, the said organic base contains at least one
sp.sup.3-hybridized carbon or an SF.sub.5 as fluorophoric carbon or
sulphur, respectively.
[0040] Advantageously, the said organic base contains at least one
trivalent phosphorus or nitrogen atom as basic function, this atom,
it goes without saying, containing a proton-accepting lone
pair.
[0041] In order for the process to be particularly advantageous,
the said base needs to be stable in very acidic and/or very
dehydrating medium (medium similar to olea [also referred to by
some as oleums]).
[0042] Another aim of the present invention is to provide compounds
which allow the organic bases to be released from their complexes
with several units of hydrofluoric acid, and in particular using
compositions containing a high proportion of hydrofluoric acid - in
general at least two units of hydrofluoric acid, advantageously at
least 3 and preferably at least 4 units of hydrofluoric acid.
[0043] These aims and others which will become apparent later are
achieved by means of the hydrogen fluorosulphonate of an organic
base; it is desirable for the said organic base, including the
combined acid, to have at least one basic function whose pKa is
(measured or brought into aqueous phase) not more than 10,
advantageously not more than 8, preferably not more than 6. It is
desirable for this pKa to be positive and advantageously at least
equal to 1, preferably at least equal to 2. Thus, organic bases
whose pKa is between 1 and 8, preferably 2 and 6 (limits included)
are preferred.
[0044] Organic bases whose hydrogen fluorosulphonate is targeted by
the present invention, and which contain at least one fluorine
atom, advantageously at least two fluorine atoms, are of special
industrial interest. This or at least one of these fluorines is
advantageously borne by an atom which has no aromatic nature (i.e.
by an atom which is not a member of an aromatic ring) this
fluorophoric atom (i.e. fluorine-bearing atom), when it is carbon,
is preferably sp.sup.3-hybridized; besides the fluorine atom which
gives this fluorophoric atom its title, the latter atom
advantageously bears one or two (identical or different) halogen
atoms [preferably chosen from light halogens, i.e. chlorine or
fluorine].
[0045] In other words, the said organic base whose hydrogen
fluorosulphonate is targeted by the present invention,
advantageously contains at least one, preferably at least two,
fluorine atoms. It is also preferable for it to contain at least
one fluorine on an sp.sup.3-hybridized carbon, which advantageously
bears one or two (identical or different) halogen atoms [preferably
chosen from light halogens, i.e. chlorine or fluorine]. It is thus
desirable for the organic base, whose hydrogen fluorosulphonate is
targeted by the present invention, to contain as fluorophoric atom
at least one carbon or at least one chalcogen from an atomic row at
least equal to that of sulphur; organic bases which contain as
fluorophoric atom(s) at least one sp.sup.3-hybridized carbon or a
hexavalent chalcogen (which, of course, cannot be oxygen),
preferably sulphur (for example SF.sub.5), are more particularly
targeted.
[0046] Advantageously, the said fluorophoric atom (for example
sp.sup.3-hybridized carbon or hexavalent sulphur) bears at least
two fluorine atoms.
[0047] The said organic base advantageously contains, as atom
bearing the (or one of the) basic function(s) (i.e. proton
accepter), a nitrogen or a trivalent phosphorus.
[0048] Among the advantageous bases, mention may be made of
aromatic heterocycles such as pyridines, including quinolines,
which are optionally substituted, including substitution with
halogens (chlorine, fluorine, bromine, etc.) and optionally
bearing, indirectly or, more advantageously, directly, at least one
fluorophoric atom as defined above.
[0049] These bases advantageously correspond to the following
formula:
Ar-L-'A-F.sub.q(R).sub.(v-q)
[0050] with Ar representing a base of-aromatic nature in which the
hetero atom bearing the (or one of the) basic function(s) (i.e.
proton accepter) is either endocyclic (as in the case of pyridine
or quinoline) or exocyclic (as in anilines);
[0051] with L representing a bond between Ar and 'A;
[0052] with 'A representing the fluorophoric atom as defined
above;
[0053] q represents the number of fluorine atoms borne by the said
fluorophoric atom and is at least equal to one and not more than
v;
[0054] v represents the residual valency (i.e. valency available
after the bond between L and 'A has been taken into account) of the
fluorophoric atom;
[0055] the groups R, which may be identical or different, (of
course when v>q) represent halogens, hydrogen atoms, a
carbon-based chain or can contain one or more other fluorophoric
atoms.
[0056] R can attach to a position of Ar to form a ring (this ring
advantageously being 4- to 8-membered, preferably 5- to
7-membered); in this case, R can advantageously take the values of
L and in particular can simply be a chalcogen (in particular oxygen
or sulphur) or a single bond.
[0057] L is advantageously chosen from a single bond, a chalcogen
atom and a divalent carbon-based radical which can contain one or
more fluorophoric atoms. In the case of a divalent carbon-based
radical, the bond between L and Ar can be an sp.sup.2
carbon-chalcogen bond; moreover, it may be advantageous for the
bond between L and the fluorophoric atom to be a
chalcogen-fluorophoric atom bond.
[0058] Ar can optionally be substituted on its available ring
members, including substitution with halogens (chlorine, fluorine,
bromine, etc.) and/or with other substituents corresponding to the
formula: -L-'A-F.sub.q(R).sub.(v-q) detailed above: thus, Ar
represents a base of aromatic nature in which the hetero atom
bearing the (or one of the) basic function(s)-(i.e. a proton
accepter) is either endocyclic (as in the case of pyridine or
quinoline) or exocyclic (as in anilines).
[0059] Ar advantageously contains not more than about 40 carbon
atoms, preferably not more than about 30, each R advantageously
containing not more than about 10 carbon atoms, preferably not more
than 8. L advantageously contains not more than about 10 carbon
atoms, preferably not more than 8.
[0060] The total number of carbon atoms in the base is
advantageously not more than about 50 carbon atoms, preferably not
more than 30 carbon atoms.
[0061] Mention should be made of a base sub-family in which
'A-F.sub.q(R).sub.(v-q) represents a perfluoro radical (i.e.
Rf=C.sub.nF.sub.2n+1).
[0062] Mention should be made of a base sub-family in which L
represents a single bond or a chalcogen atom.
[0063] The intersection between these two sub-families is
particularly advantageous.
[0064] The present invention thus relates to a composition
containing both hydrofluoric acid and a hydrogen sulphonate, in
which composition the molar ratio between the hydrofluoric acid and
the basic functions of the said organic base (HF/basic functions of
the said organic base) is at least equal to 2, advantageously equal
to 3, preferably equal to 4.
[0065] The water content in the said composition is advantageously
such that the number of molecules of water in the composition is
not more than half (advantageously a quarter, preferably a tenth)
of the number (expressed as equivalents) of basic functions present
in the composition.
[0066] In addition, the composition can also contain sulphuric
acid.
[0067] Needless to say, it can also contain any product used in the
previous steps of the synthesis of the said organic base.
[0068] The non-limiting examples which follow illustrate the
invention.
[0069] General Conditions and General Procedure
[0070] The crude reaction products were analysed by gas
chromatography.
[0071] Principle
[0072] As indicated in the above description, it is economically
important and was technically conceivable to recover the excess HF
used to fluorinate the last but one precursor of the pTFMA by
distillation after the step of lysis of the carbamoyl fluoride into
pTFMA hydrofluoride: 1
[0073] After unsuccessfully attempting to recover the "free" HF by
distilling the pTFMA hydrofluoride/HF mixture, the lysis technique
was tested according to a particularly advantageous embodiment of
the present invention, by addition of 98%sulphuric acid to the
pTFMA hydrofluoride/HF mixture.
Example 1 (COMPARATIVE)
Distillation of HF Using a pTFMA Hydrofluoride/HF Mixture
[0074] The assay for this sample (neutralization, PTFMA assay by
HPLC, assay of the fluorides by ion chromatography) gives the
following proportions:
[0075] pTFMA/HF=59/41
[0076] i.e. 5.6 equivalents of HF relative to the PTFMA.
[0077] Distillation Procedure
[0078] Experimentally, the pTFMA hydrofluoride/HF mixture was
heated in a 500 ml Teflon PFA reactor under a stream of nitrogen.
The HF distilled off was trapped out in bubblers with potassium
hydroxide, the fluorides being assayed by ion chromatography.
[0079] The distillation vessel was heated until an HF distillation
plateau was reached without degradation of the
trifluoromethylaniline.
[0080] The results are collated below:
1 Test Initial pTFMA Dura- pTFMA* No. hydrofluoride HF T.degree.
tion HF distilled off found a pTFMA: 60.degree. C. 1 h 30 0.078
mol, i.e. 96% 0.198 mol 8.5% of the HF.sub.free: 0.911 mol initial
"free" HF b crude product 90.degree. C. 1 h 00 0.162 mol, i.e. 100%
from a) 19.5% of the remaining "free" HF Total 26% of the 98%
initial "free" HF *assay by HPLC after neutralization.
[0081] It appears that heating the PTFMA hydrofluoride/HF mixture
allows only 26% of the "free" HF (HF not in hydrofluoride form)
initially present to be distilled off.
[0082] The remaining HF associated with the PTFMA would appear to
correspond to a complex of approximate formula:
pTFMA.multidot.4HF
[0083] These HF-base complexes are known to be difficult to
decompose by simple heating.
[0084] In conclusion, heating of the pTFMA hydrofluoride/HF crude
reaction product does not allow all of the HF initially present to
be recycled.
EXAMPLE 2
Tests of Recovery of HF from Carbamoyl Fluoride-6HF
[0085] It was possible to observe that simple addition of 98%
sulphuric acid to carbamoyl fluoride led to a considerable and
immediate evolution of gas.
[0086] Infrared analysis of the gas formed demonstrates that it is
essentially carbon dioxide. It appeared that the result of the
above case was found. However, analyses on the crude reaction
product and further studies made it possible to explain the
formation of CO.sub.2 by reaction between carbamoyl fluoride and
H.sub.2SO.sub.4: the sulphuric acid (even at 100%) reacts with it
to form pTFMA fluorosulphonate and CO.sub.2. 2
2TABLE II Treatment of the pTFMA.nHF mixture with H.sub.2SO.sub.4 3
H.sub.2SO.sub.4: quality and No. of equiv. relative to the pTFMA
T.degree., duration HF evolved pTFMA RY HF not distille d off
pTFMA; HF: 100% H.sub.2SO.sub.4 60.degree. C., 2 h 0.517 98% 1.1
0.098 mol; mol, equiv. HF: 0.629 mol i.e. of HF % i.e. 5.4 5.3 i.e.
= equiv. 2.1 equiv. 90.degree. C., 1 h equiv. 0.1 equiv. of free HF
pTFMA; HF: 98% H.sub.2SO.sub.4 60-65.degree. C., 0.65 97% HF: 1.16
0.097 mol; 2 h mol, equiv., HF: 0.709 mol i.e. i.e. i.e. 6.3 6.7
0.16 equiv. 2.08 equiv. 90.degree. C., 1 h equiv. equiv. free HF
pTFMA; HF: 98% H.sub.2SO.sub.4 65.degree. C., 2 h 0.537 96.5% HF:
1.85 0.098 mol; mol, equiv., HF: 0.715 mol i.e. i.e. i.e. 6.3 5.48
0.85 equiv. 4 equiv. 90.degree. C., 1 h equiv. equiv. of free HF
pTFMA; HF: 98% H.sub.2SO.sub.4 60-65.degree. C., HF: 1.47 6.6
equiv. HF 1 h 30 equiv., a) 1.13 i.e. equiv. 3 0.47 equiv. free HF
b) additional 90.degree. C., 1 h 98% HF: 1 1 equiv. equiv., i.e. 0
equiv. free HF
[0087] To the Applicant's knowledge, this water-free "lysis" of a
carbamoyl halide function with sulphuric acid has never been
described in the literature.
[0088] A 6-centre mechanism can be put forward to explain this
reaction, the CF.sub.3 group strongly activating the carbamoyl
fluoride function: 4
[0089] The pTFMA fluorosulphonate, characterized by .sup.19F NMR
and IR was also synthesized by the action of fluorosulphonic acid
HFSO.sub.3 on PTFMA.
[0090] pTFMA fluorosulphonate is a solid which is rapidly
hydrolysed by atmospheric moisture into pTFMA hydrogen sulphate:
5
[0091] Experimentally, the tests summarized in Table II were
carried out in the following way:
[0092] 98 or 100% sulphuric acid was added to the above solutions
at 20.degree. C., leading to an immediate evolution of
CO.sub.2.
[0093] After adding the H.sub.2SO.sub.4, the homogeneous reaction
mixture was heated, under a stream of nitrogen, to remove the HF,
which was trapped out in bubblers containing potassium hydroxide.
The fluorides obtained were assayed by ion chromatography.
[0094] After cooling to room temperature, the reaction media were
analysed. After anhydrous neutralization with pentylamine, the
pTFMA was assayed by HPLC.
[0095] From the results obtained, the following conclusions can
thus be drawn:
[0096] The action of about 2 equivalents of H.sub.2SO.sub.4 (98 or
100%) on a mixture, HF (5 to 6 equivalents of HF relative to the
carbamoyl fluoride), followed by heating to 90.degree. C. allows
virtually all of the initial "free" HF to be removed.
[0097] After removal of the HF, the medium obtained is homogeneous
and liquid, and corresponds to a solution of pTFMA fluorosulphonate
in H.sub.2SO.sub.4 containing a small amount of HF (0.1 to 0.2
equivalent of initial "free" HF).
[0098] The use of 4 equivalents of 98% H.sub.2SO.sub.4 limits the
number of equivalents of HF distilled off. This can be explained by
the water provided by the 98% H.sub.2SO.sub.4, which can hydrolyse
the carbamoyl fluoride into PTFMA hydrofluoride. In this case,
HF-base complexes can be formed between the base and the HF and
limit the distillation of the HF, as has already been observed.
[0099] This type of HF-base complex should not be formed between
pTFMA fluorosulphonate and HF.
[0100] After neutralization of the crude reaction product which has
been degassed in respect of HF, the pTFMA was obtained in a yield
of about 97-98% (HPLC assay).
[0101] In conclusion, the addition of 2 equivalents of 98 or 100%
H.sub.2SO.sub.4 to the crude product from the fluorination of pTCMI
2 makes it possible, by heating, to recycle virtually all of the
free HF initially present and to obtain a homogeneous liquid
solution of pTFMA fluorosulphonate 7 in about 1 equivalent of
H.sub.2SO.sub.4.
[0102] Using the solution of pTFMA fluorosulphonate in sulphuric
acid after distillation of the HF, the PTFMA can be obtained by
neutralization with aqueous sodium hydroxide and extraction with
methylene chloride. The yield for this neutralization and
extraction step is greater than 98%.
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