U.S. patent application number 10/213538 was filed with the patent office on 2009-06-04 for n-hydroxy-n'-nitrourea and related compounds as high energy density materials.
Invention is credited to Jeffrey C. Bottaro, Allen L. Dodge, Paul E. Penwell, Mark A. Petrie.
Application Number | 20090139618 10/213538 |
Document ID | / |
Family ID | 40674529 |
Filed Date | 2009-06-04 |
United States Patent
Application |
20090139618 |
Kind Code |
A1 |
Petrie; Mark A. ; et
al. |
June 4, 2009 |
N-hydroxy-N'-nitrourea and related compounds as high energy density
materials
Abstract
Novel compounds are provided in the form of a salt having the
structure of formula (I) or formula (II) ##STR00001## wherein:
R.sup.1 is selected from the group consisting of H,
C.sub.1-C.sub.24 alkyl, C.sub.2-C.sub.24 alkenyl, C.sub.2-C.sub.24
alkynyl, C.sub.5-C.sub.20 aryl, C.sub.6-C.sub.24 alkaryl, and
C.sub.6-C.sub.24 aralkyl; R.sup.2 is H, C.sub.1-C.sub.24 alkyl or
nitro; X is O or NR.sup.3 in which R.sup.3 is H, C.sub.1-C.sub.24
alkyl or nitro; Z.sup.m+ is a monovalent cation, a divalent cation,
or a trivalent cation; M.sup.+ is an alkali metal cation; and m and
n are 1, 2 or 3, with the proviso that the compound contains at
least one nitro group. Exemplary such compounds are the ammonium
salt of the N-hydroxyl-N'-nitrourea (NHNU) monoanion and the
disodium salt of the NHNU dianion. Also provided, as novel
compositions of matter, are N-hydroxyl-N'-nitrourea and
N-hydroxyl-N-nitroguanidine in electronically neutral form. The
compounds are useful in a variety of contexts, but are primarily
useful as high energy oxidizing agents in explosive compositions,
propellant formulations, gas-generating compositions, and the like.
Compositions containing the compounds are also provided, including
energetic compositions, as are methods for synthesizing the
compounds.
Inventors: |
Petrie; Mark A.; (Cupertino,
CA) ; Bottaro; Jeffrey C.; (Mountain View, CA)
; Penwell; Paul E.; (El Granada, CA) ; Dodge;
Allen L.; (Newark, CA) |
Correspondence
Address: |
MINTZ, LEVIN, COHN, FERRIS, GLOVSKY AND POPEO, P.C
5 Palo Alto Square - 6th Floor, 3000 El Camino Real
PALO ALTO
CA
94306-2155
US
|
Family ID: |
40674529 |
Appl. No.: |
10/213538 |
Filed: |
August 6, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60310707 |
Aug 6, 2001 |
|
|
|
Current U.S.
Class: |
149/19.1 |
Current CPC
Class: |
C07C 291/04 20130101;
C06B 25/34 20130101 |
Class at
Publication: |
149/19.1 |
International
Class: |
C06B 45/10 20060101
C06B045/10 |
Goverment Interests
REFERENCE TO GOVERNMENT SUPPORT
[0002] This invention was funded by the United States Air Force
Office of Scientific Research under Contract No. F49620-00-C-0033.
The United States Government has certain rights in this invention.
Claims
1. A compound in the form of a salt having the structure of formula
(I) ##STR00014## wherein: R.sup.1 is selected from the group
consisting of H, C.sub.1-C.sub.24 alkyl, C.sub.2-C.sub.24 alkenyl,
C.sub.2-C.sub.24 alkynyl, C.sub.5-C.sub.20 aryl, C.sub.6-C.sub.24
alkaryl, and C.sub.6-C.sub.24 aralkyl; R.sup.2 is H,
C.sub.1-C.sub.24 alkyl or nitro; X is O or NR.sup.3 in which
R.sup.3 is H, C.sub.1-C.sub.24 alkyl or nitro; Z.sup.m+ is a
monovalent cation, a divalent cation, or a trivalent cation; and m
and n are 1, 2 or 3, with the proviso that the compound contains at
least one nitro group.
2. The compound of claim 1, wherein R.sup.1 is H, R.sup.2 is nitro,
X is O, such that the compound is a salt of N-hydroxyl-N'-nitrourea
monoanion.
3. The compound of claim 2, wherein m and n are 1, and Z is
ammonium ion, such that the compound is N-hydroxyl-N'-nitrourea,
ammonium salt.
4. A compound in the form of a salt having the structure of formula
(II) ##STR00015## wherein: R.sup.1 is selected from the group
consisting of H, C.sub.1-C.sub.24 alkyl, C.sub.2-C.sub.24 alkenyl,
C.sub.2-C.sub.24 alkynyl, C.sub.5-C.sub.20 aryl, C.sub.6-C.sub.24
alkaryl, and C.sub.6-C.sub.24 aralkyl; R.sup.2 is H,
C.sub.1-C.sub.24 alkyl or nitro; X is O or NR.sup.3 in which
R.sup.3 is H, C.sub.1-C.sub.24 alkyl or nitro; and M is an alkali
metal, with the proviso that the compound contains at least one
nitro group.
5. The compound of claim 4, wherein R.sup.1 is H, R.sup.2 is nitro,
X is O, and M is potassium, such that the compound is
N-hydroxyl-N'-nitrourea, dipotassium salt.
6. N-hydroxyl-N'-nitrourea.
7. N-hydroxyl-N'-nitroguanidine.
8. An energetic composition comprising the compound of claim 2 and
a polymeric binder.
9. An energetic composition comprising the compound of claim 3 and
a polymeric binder.
10. An energetic composition comprising the compound of claim 5 and
a polymeric binder.
11. A propellant composition comprising the compound of claim 2, a
polymeric binder, a metallic fuel, and an igniter compound.
12. A propellant composition comprising the compound of claim 3, a
polymeric binder, a metallic fuel, and an igniter compound.
13. A propellant composition comprising the compound of claim 5, a
polymeric binder, a metallic fuel, and an igniter compound.
14. A gas-generating composition comprising the compound claim 2, a
polymeric binder, a nitrogenous fuel, and an igniter compound.
15. A gas-generating composition comprising the compound claim 3, a
polymeric binder, a nitrogenous fuel, and an igniter compound.
16. A gas-generating composition comprising the compound claim 5, a
polymeric binder, a nitrogenous fuel, and an igniter compound.
17. A method for synthesizing a salt of N-hydroxyl-N'-nitrourea,
comprising treating a basic salt of a lower alkyl nitrocarbamate
and a monovalent cation with a hydroxide-releasing base in the
presence of aqueous hydroxylamine until a salt of the monovalent
cation and di-anionic N-hydroxyl-N'-nitrourea precipitates.
18. A method for synthesizing N-hydroxyl-N'-nitrourea, comprising
carrying out the method of claim 17 and thereafter processing the
precipitate with a sulfuric acid solution to obtain
N-hydroxyl-N'-nitrourea in electronically neutral form.
19. A method for synthesizing the ammonium salt of
N-hydroxyl-N'-nitrourea, comprising: carrying out the method of
claim 18; and re-dissolving the N-hydroxyl-N'-nitrourea in a
solvent containing a stoichiometric amount of ammonia.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority under 35 U.S.C.
.sctn.119(e)(1) to Provisional U.S. Patent Application Ser. No.
60/310,707, filed Aug. 6, 2001, the disclosure of which is
incorporated by reference herein.
TECHNICAL FIELD
[0003] The present invention relates generally to energetic
materials, and more particularly relates to novel chemical
compounds useful, inter alia, as high energy oxidizing agents.
Energetic compositions containing the compounds are also provided,
as are methods for synthesizing the novel compounds.
BACKGROUND
[0004] In developing new energetic compounds, a number of factors
come into play. For example, heat of formation, density, melting
and decomposition temperatures, carbon content and, generally,
nitrogen content, are properties that must be considered. Energetic
compounds should display good thermal and shock properties and have
high heats of formation. It is generally preferred that an
energetic compound have a melting point above about 100.degree. C.,
an exothermic heat of combustion, a positive heat of formation
.DELTA.H.sub.f, and a high decomposition temperature. A relatively
large separation between melting point and decomposition
temperature is preferred, so that an energetic composition may be
melt cast from the selected compound. Finally, it is of course
preferred that an energetic compound be relatively simple and
straightforward to synthesize in high yield.
[0005] A number of energetic compounds are known to be useful as
oxidizers, explosives, and the like. Energetic compounds have also
been disclosed as useful to inflate automobile and aircraft
occupant restraint bags. Previously known materials, however, are
generally limited in one or more ways, e.g., they are overly
impact-sensitive, difficult to synthesize on a large scale, not
sufficiently energetic, excessively hygroscopic, or unstable at
basic or slightly acidic pH. In addition, energetic compositions
used to inflate occupant restraint bags in automobiles and aircraft
typically contain potentially toxic heavy metal igniter materials,
e.g., mercury compounds, Pb(N.sub.3).sub.2, or the like.
[0006] The present invention provides a new class of compounds that
overcomes the aforementioned limitations in the art. The energetic
compounds to which the invention pertains are commonly referred to
as "secondary" explosives, i.e., compounds whose energy is released
after activation by initiator compounds, also termed "primary"
explosives. The compounds now provided herein meet all of the
above-mentioned preferred criteria, and outperform conventional
energetic compounds in a number of ways. For example, higher
O.sub.2 density is provided than obtained with conventional
secondary explosives such as ammonium nitrate. In addition, the
novel compounds are highly energetic while not overly impact
sensitive, and are straightforward to synthesize in high yield.
SUMMARY OF THE INVENTION
[0007] It is accordingly an object of the invention to address the
above-mentioned need in the art by providing novel compounds that
are useful as energetic materials, e.g., as high energy oxidizing
agents.
[0008] It is still another object of the invention to provide
energetic compositions containing one or more of the novel
compounds.
[0009] It is yet another object of the invention to provide such
energetic compositions in the form of propellant formulations,
explosive compositions, and the like.
[0010] It is a further object of the invention to provide
gas-generating compositions containing one or more of the novel
compounds.
[0011] It is yet a further object of the invention to provide
methods for synthesizing the novel compounds.
[0012] Additional objects, advantages, and novel features of the
invention will be set forth in part in the description that
follows, and in part will become apparent to those skilled in the
art upon examination of the following, or may be learned by
practice of the invention.
[0013] In one embodiment, the invention provides a compound in the
form of a salt having the structure of formula (I)
##STR00002##
wherein: [0014] R.sup.1 is selected from the group consisting of H,
C.sub.1-C.sub.24 alkyl, C.sub.2-C.sub.24 alkenyl, C.sub.2-C.sub.24
alkynyl, C.sub.5-C.sub.20 aryl, C.sub.6-C.sub.24 alkaryl, and
C.sub.6-C.sub.24 aralkyl; [0015] R.sup.2 is H, C.sub.1-C.sub.24
alkyl or nitro; [0016] X is O or NR.sup.3 in which R.sup.3 is H,
C.sub.1-C.sub.24 alkyl or nitro; [0017] Z.sup.m+ is a monovalent
cation, a divalent cation, or a trivalent cation; and [0018] m and
n are 1, 2 or 3, [0019] with the proviso that the compound contains
at least one nitro group.
[0020] In another embodiment, the invention is directed to a
compound having the structure of formula (II)
##STR00003##
wherein: [0021] R.sup.1 is selected from the group consisting of H,
C.sub.1-C.sub.24 alkyl, C.sub.2-C.sub.24 alkenyl, C.sub.2-C.sub.24
alkynyl, C.sub.5-C.sub.20 aryl, C.sub.6-C.sub.24 alkaryl, and
C.sub.6-C.sub.24 aralkyl; [0022] R.sup.2 is H, C.sub.1-C.sub.24
alkyl or nitro; [0023] X is O or NR.sup.3 in which R.sup.3 is H,
C.sub.1-C.sub.24 alkyl or nitro; and [0024] M is an alkali metal,
[0025] with the proviso that the compound contains at least one
nitro group.
[0026] In another embodiment, the invention is directed to a
compound having the structure of formula (III)
##STR00004##
also referred to herein as N-hydroxyl-N'-nitrourea (NHNU), in
electronically neutral form.
[0027] In still another embodiment, the invention is directed to a
compound having the structure of formula (IV)
##STR00005##
also referred to herein as N-hydroxyl-N-nitroguanidine, in
electronically neutral form.
[0028] In another embodiment of the invention, energetic
compositions are provided containing one or more of the novel
compounds as energetic materials. These energetic compositions may
take any number of forms and have a variety of uses, such as in
rocket propellant formulations (including both solid and solution
propellants), liquid monopropellants, bipropellant and
tripropellant compositions, pyrotechnics, firearms, and the like.
In addition, the compounds of the invention are useful in
energetic, gas-generating compositions for inflating automotive or
aircraft occupant restraint devices. As will be appreciated by
those skilled in the art, the aforementioned uses are exemplary in
nature and not intended to represent a comprehensive list of
possibilities.
[0029] In a further embodiment, a method is provided for
synthesizing N-hydroxyl-N'-nitrourea and salts and analogs thereof,
by treating a basic salt of a lower alkyl nitrocarbamate and a
monovalent cation with a hydroxide-releasing base in the presence
of aqueous hydroxylamine until a salt of the cation and di-anionic
N-hydroxyl-N'-nitrourea precipitates. The salt may be, for example,
a sodium salt or a potassium salt. The electronically neutral form
of N-hydroxyl-N'-nitrourea may then be obtained by processing the
precipitate with an acid, preferably in the form of a sulfuric acid
solution. The precipitate may or may not be isolated prior to
processing with the sulfuric acid solution. The method may also
include filtering the N-hydroxyl-N'-nitrourea obtained, and may
further include crystallizing the filtered N-hydroxyl-N'-nitrourea.
The ammonium salt of N-hydroxyl-N'-nitrourea, one preferred
compound herein, may be prepared by redissolving the electronically
neutral N-hydroxyl-N'-nitrourea obtained after filtering and
crystallization in a solvent containing a stoichiometric amount of
ammonia.
[0030] The compounds of the invention, as alluded to above, are
advantageous in numerous ways. For example, the compounds: [0031]
are straightforward to synthesize and scale up, in high yield;
[0032] exhibit low impact sensitivity, on the order of 50% less
than that associated with RDX
(cyclo-1,3,5-tri-methylene-2,4,6-trinitramine; also referred to as
"cyclonite") and HMX
((1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane); [0033] are
powerful oxidizing agents, comparable to ammonium nitrate (AN) in
oxidizing power, while burning more readily than AN; [0034] are
substantially less hygroscopic than other high energy density
compounds, such as ammonium dinitramide (ADN), even at 90% relative
humidity; [0035] have a peak decomposition temperature (T.sub.d) as
determined by Differential Scanning Calorimetry (DSC), of from
about 140.degree. C. to about 160.degree. C.; and [0036] are stable
across a wide pH range and thus adaptable in a number of
applications.
[0037] It is particularly interesting to note that NHNU and salts
thereof exhibit long-term stability upon storage, in both light and
dark conditions, in contrast to both N-hydroxyurea (NHU) and
N-nitrourea (NNU), both of which readily decompose to give gaseous
products. Storage stability is of course of utmost importance in
any commercial application, and both NHU and NNU readily decompose
to give gaseous products.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 illustrates a molecule of N-hydroxyl-N'-nitrourea,
synthesized and characterized as described in Example 2, as
determined by x-ray crystallography.
[0039] FIG. 2 shows the crystal structure of
N-hydroxyl-N'-nitrourea, synthesized and characterized as described
in Example 2.
[0040] FIG. 3 illustrates a molecule of the ammonium salt of
N-hydroxyl-N'-nitrourea, synthesized and characterized as described
in Example 4, as determined by x-ray crystallography.
[0041] FIG. 4 illustrates the unit cell contents of
N-hydroxyl-N'-nitrourea, ammonium salt, syntheszied and
characterized as described in Example 4.
[0042] FIG. 5 illustrates a molecule of
N-hydroxyl-N'-nitroguanidine, synthesized and characterized as
described in Example 5, as determined by x-ray crystallography.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0043] Unless otherwise indicated, the invention is not limited to
specific molecular structures, analogs, composition components
(e.g., igniter materials, gas-generating fuels, binders, secondary
oxidizers), synthetic methods, methods of manufacture, or the like,
as such may 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.
[0044] 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 compound" includes a single compound as well as a
combination or mixture of two or more compounds, reference to "a
substituent" includes a single substituent as well as two or more
substituents that may be the same or different, and the like.
[0045] In this specification and in the claims that follow,
reference will be made to a number of terms, which shall be defined
to have the following meanings:
[0046] As used herein, the phrase "having the formula" or "having
the structure" is not intended to be limiting and is used in the
same way that the term "comprising" is commonly used.
[0047] The term "alkyl" as used herein refers to a branched or
unbranched saturated hydrocarbon group typically, although not
necessarily, containing 1 to about 24 carbon atoms, such as methyl,
ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, octyl,
decyl, and the like, as well as cycloalkyl groups such as
cyclopentyl, cyclohexyl and the like. Generally, although again not
necessarily, alkyl groups herein contain 1 to about 18 carbon
atoms, preferably 1 to about 12 carbon atoms. The term "lower
alkyl" intends an alkyl group of 1 to 6 carbon atoms. Preferred
substituents identified as "C.sub.1-C.sub.6 alkyl" or "lower alkyl"
contain 1 to 3 carbon atoms, and particularly preferred such
substituents contain 1 or 2 carbon atoms (i.e., methyl and ethyl).
"Substituted alkyl" refers to alkyl substituted with one or more
substituent groups, and the terms "heteroatom-containing alkyl" and
"heteroalkyl" refer to alkyl in which at least one carbon atom is
replaced with a heteroatom, as described in further detail infra.
If not otherwise indicated, the terms "alkyl" and "lower alkyl"
include linear, branched, cyclic, unsubstituted, substituted,
and/or heteroatom-containing alkyl or lower alkyl,
respectively.
[0048] The term "alkenyl" as used herein refers to a linear,
branched, or cyclic hydrocarbon group of 2 to about 24 carbon atoms
containing at least one double bond, such as ethenyl, n-propenyl,
isopropenyl, n-butenyl, isobutenyl, octenyl, decenyl, tetradecenyl,
hexadecenyl, eicosenyl, tetracosenyl, and the like. Generally,
although again not necessarily, alkenyl groups herein contain 2 to
about 18 carbon atoms, preferably 2 to 12 carbon atoms. The term
"lower alkenyl" intends an alkenyl group of 2 to 6 carbon atoms,
and the specific term "cycloalkenyl"intends a cyclic alkenyl group,
preferably having 5 to 8 carbon atoms. The term "substituted
alkenyl" refers to alkenyl substituted with one or more substituent
groups, and the terms "heteroatom-containing alkenyl" and
"heteroalkenyl" refer to alkenyl in which at least one carbon atom
is replaced with a heteroatom. If not otherwise indicated, the
terms "alkenyl" and "lower alkenyl" include linear, branched,
cyclic, unsubstituted, substituted, and/or heteroatom-containing
alkenyl and lower alkenyl, respectively.
[0049] The term "alkynyl" as used herein refers to a linear or
branched hydrocarbon group of 2 to 24 carbon atoms containing at
least one triple bond, such as ethynyl, n-propynyl, and the like.
Generally, although again not necessarily, alkynyl groups herein
contain 2 to about 18 carbon atoms, preferably 2 to 12 carbon
atoms. The term "lower alkynyl" intends an alkynyl group of 2 to 6
carbon atoms. The term "substituted alkynyl" refers to alkynyl
substituted with one or more substituent groups, and the terms
"heteroatom-containing alkynyl" and "heteroalkynyl" refer to
alkynyl in which at least one carbon atom is replaced with a
heteroatom. If not otherwise indicated, the terms "alkynyl" and
"lower alkynyl" include linear, branched, unsubstituted,
substituted, and/or heteroatom-containing alkynyl and lower
alkynyl, respectively.
[0050] The term "aryl" as used herein, and unless otherwise
specified, refers to an aromatic substituent containing a single
aromatic ring or multiple aromatic rings that are fused together,
directly linked, or indirectly linked (such that the different
aromatic rings are bound to a common group such as a methylene or
ethylene moiety). Preferred aryl groups contain 5 to 20 carbon
atoms, and particularly preferred aryl groups contain 5 to 14
carbon atoms. Exemplary aryl groups contain one aromatic ring or
two fused or linked aromatic rings, e.g., phenyl, naphthyl,
biphenyl, diphenylether, diphenylamine, benzophenone, and the like.
"Substituted aryl" refers to an aryl moiety substituted with one or
more substituent groups, and the terms "heteroatom-containing aryl"
and "heteroaryl" refer to aryl substituent in which at least one
carbon atom is replaced with a heteroatom, as will be described in
further detail infra. If not otherwise indicated, the term "aryl"
includes unsubstituted, substituted, and/or heteroatom-containing
aromatic substituents.
[0051] The term "alkaryl" refers to an aryl group with an alkyl
substituent, and the term "aralkyl" refers to an alkyl group with
an aryl substituent, wherein "aryl" and "alkyl" are as defined
above. Preferred aralkyl groups contain 6 to 24 carbon atoms, and
particularly preferred aralkyl groups contain 6 to 16 carbon atoms.
Examples of aralkyl groups include, without limitation, benzyl,
2-phenyl-ethyl, 3-phenyl-propyl, 4-phenyl-butyl, 5-phenyl-pentyl,
4-phenylcyclohexyl, 4-benzylcyclohexyl, 4-phenylcyclohexylmethyl,
4-benzylcyclohexylmethyl, and the like. Alkaryl groups include, for
example, p-methylphenyl, 2,4-dimethylphenyl, p-cyclohexylphenyl,
2,7-dimethylnaphthyl, 7-cyclooctylnaphthyl,
3-ethyl-cyclopenta-1,4-diene, and the like.
[0052] The terms "halo" and "halogen" are used in the conventional
sense to refer to a chloro, bromo, fluoro, or iodo substituent.
[0053] The term "heteroatom-containing" as in a
"heteroatom-containing alkyl group" (also termed a "heteroalkyl"
group) or a "heteroatom-containing aryl group" (also termed a
"heteroaryl" group) refers to a molecule, linkage, or substituent
in which one or more carbon atoms are replaced with an atom other
than carbon, e.g., nitrogen, oxygen, sulfur, phosphorus, or
silicon, typically nitrogen, oxygen, or sulfur. Similarly, the term
"heteroalkyl" refers to an alkyl substituent that is
heteroatom-containing, the term "heterocyclic" refers to a cyclic
substituent that is heteroatom-containing, the terms "heteroaryl"
and "heteroaromatic respectively refer to "aryl" and "aromatic"
substituents that are heteroatom-containing, and the like. Examples
of heteroalkyl groups include alkoxyaryl, alkylsulfanyl-substituted
alkyl, N-alkylated amino alkyl, and the like. Examples of
heteroaryl substituents include pyrrolyl, pyrrolidinyl, pyridinyl,
quinolinyl, indolyl, pyrimidinyl, imidazolyl, 1,2,4-triazolyl,
tetrazolyl, etc., and examples of heteroatom-containing alicyclic
groups are pyrrolidino, morpholino, piperazino, piperidino,
etc.
[0054] By "substituted," as in "substituted alkyl," "substituted
aryl," and the like, as alluded to in some of the aforementioned
definitions, is meant that in the alkyl, aryl, or other moiety, at
least one hydrogen atom bound to a carbon (or other) atom is
replaced with one or more non-hydrogen substituents. Examples of
such substituents include, without limitation: functional groups
such as halo, hydroxyl, sulfhydryl, C.sub.1-C.sub.24 alkoxy,
C.sub.2-C.sub.24 alkenyloxy, C.sub.2-C.sub.24 alkynyloxy,
C.sub.5-C.sub.20 aryloxy, acyl (including C.sub.2-C.sub.24
alkylcarbonyl (--CO-alkyl) and C.sub.6-C.sub.20 arylcarbonyl
(--CO-aryl)), acyloxy (--O-acyl), C.sub.2-C.sub.24 alkoxycarbonyl
(--(CO)-O-alkyl), C.sub.6-C.sub.20 aryloxycarbonyl (--(CO)-O-aryl),
halocarbonyl (--CO)-X where X is halo), C.sub.2-C.sub.24
alkylcarbonato (--O--(CO)--O-alkyl), C.sub.6-C.sub.20 arylcarbonato
(--O--(CO)--O-aryl), carboxy (--COOH), carboxylato (--COO.sup.-),
carbamoyl (--(CO)--NH.sub.2), mono-(C.sub.1-C.sub.24
alkyl)-substituted carbamoyl (--(CO)--NH(C.sub.1-C.sub.24 alkyl)),
di-(C.sub.1-C.sub.24 alkyl)-substituted carbamoyl
(--(CO)--N(C.sub.1-C.sub.24 alkyl).sub.2), mono-substituted
arylcarbamoyl (--(CO)--NH-aryl), thiocarbamoyl (--(CS)--NH.sub.2),
carbamido (--NH--(CO)--NH.sub.2), cyano(--C.ident.N), isocyano
(--N.sup.+.ident.C.sup.-), cyanato (--O--C.ident.N), isocyanato
(--O--N.sup.+.ident.C.sup.-), isothiocyanato (--S--C.ident.N),
azido (--N.dbd.N.sup.+.dbd.N.sup.-), formyl (--(CO)--H), thioformyl
(--(CS)--H), amino (--NH.sub.2), mono- and di-(C.sub.1-C.sub.24
alkyl)-substituted amino, mono- and di-(C.sub.5-C.sub.20
aryl)-substituted amino, C.sub.2-C.sub.24 alkylamido
(--NH--(CO)-alkyl), C.sub.6-C.sub.20 arylamido (--NH--(CO)-aryl),
imino (--CR.dbd.NH where R=hydrogen, C.sub.1-C.sub.24 alkyl,
C.sub.5-C.sub.20 aryl, C.sub.6-C.sub.24 alkaryl, C.sub.6-C.sub.24
aralkyl, etc.), alkylimino (--CR.dbd.N(alkyl), where R=hydrogen,
alkyl, aryl, alkaryl, etc.), arylimino (--CR.dbd.N(aryl), where
R=hydrogen, alkyl, aryl, alkaryl, etc.), nitro (--NO.sub.2),
nitroso (--NO), sulfo (--SO.sub.2--OH), sulfonato
(--SO.sub.2--O.sup.-), C.sub.1-C.sub.24 alkylsulfanyl (--S-alkyl;
also termed "alkylthio"), arylsulfanyl (--S-aryl; also termed
"arylthio"), C.sub.1-C.sub.24 alkylsulfinyl (--(SO)-alkyl),
C.sub.5-C.sub.20 arylsulfinyl (--(SO)-aryl), C.sub.1-C.sub.24
alkylsulfonyl (--SO.sub.2-alkyl), C.sub.5-C.sub.20 arylsulfonyl
(--SO.sub.2-aryl), phosphono (--P(O)(OH).sub.2), phosphonato
(--P(O)(O.sup.-).sub.2), phosphinato (--P(O)(O.sup.-)), phospho
(--PO.sub.2), and phosphino (--PH.sub.2); and the hydrocarbyl
moieties C.sub.1-C.sub.24 alkyl (preferably C.sub.1-C.sub.18 alkyl,
more preferably C.sub.1-C.sub.12 alkyl, most preferably
C.sub.1-C.sub.6 alkyl), C.sub.2-C.sub.24 alkenyl (preferably
C.sub.2-C.sub.18 alkenyl, more preferably C.sub.2-C.sub.12 alkenyl,
most preferably C.sub.2-C.sub.6 alkenyl), C.sub.2-C.sub.24 alkynyl
(preferably C.sub.2-C.sub.18 alkynyl, more preferably
C.sub.2-C.sub.12 alkynyl, most preferably C.sub.2-C.sub.6 alkynyl),
C.sub.5-C.sub.20 aryl (preferably C.sub.5-C.sub.14 aryl),
C.sub.6-C.sub.24 alkaryl (preferably C.sub.6-C.sub.18 alkaryl), and
C.sub.6-C.sub.24 aralkyl (preferably C.sub.6-C.sub.18 aralkyl).
[0055] In addition, the aforementioned functional groups may, if a
particular group permits, be further substituted with one or more
additional functional groups or with one or more hydrocarbyl
moieties such as those specifically enumerated above. Analogously,
the above-mentioned hydrocarbyl moieties may be further substituted
with one or more functional groups or additional hydrocarbyl
moieties such as those specifically enumerated.
[0056] In one embodiment, then, the compounds of the invention are
salts having the structure of formula (I)
##STR00006##
wherein the various substituents are as follows:
[0057] R.sup.1 is H, C.sub.1-C.sub.24 alkyl (preferably
C.sub.1-C.sub.12 alkyl, more preferably C.sub.1-C.sub.6 alkyl),
C.sub.2-C.sub.24 alkenyl (preferably C.sub.2-C.sub.12 alkenyl, more
preferably C.sub.2-C.sub.6 alkenyl), C.sub.2-C.sub.24 alkynyl
(preferably C.sub.2-C.sub.12 alkynyl, more preferably
C.sub.2-C.sub.6 alkynyl), C.sub.5-C.sub.20 aryl (preferably
C.sub.5-C.sub.14 aryl), C.sub.6-C.sub.24 alkaryl (preferably
C.sub.6-C.sub.16 alkaryl), or C.sub.6-C.sub.24 aralkyl (preferably
C.sub.6-C.sub.16 aralkyl), wherein any of the aforementioned
hydrocarbyl groups are optionally substituted and/or
heteroatom-containing. Most preferably, R is H.
[0058] R.sup.2 is H, C.sub.1-C.sub.24 alkyl (preferably
C.sub.1-C.sub.12 alkyl, more preferably C.sub.1-C.sub.6 alkyl), or
nitro. Most preferably, R.sup.2 is nitro.
[0059] X is O or NR.sup.3 in which R.sup.3 is H, C.sub.1-C.sub.24
alkyl (preferably C.sub.1-C.sub.12 alkyl, more preferably
C.sub.1-C.sub.6 alkyl) or nitro. Most preferably X is O or NR.sup.3
wherein R.sup.3 is nitro.
[0060] Z.sup.m+ is a cation selected from a monovalent cation, a
divalent cation, and a trivalent cation, wherein m and n are 1, 2,
or 3. In this embodiment, a particularly preferred compound is in
the form of an ammonium salt, wherein m is 1, n is 1, and Z is
NH.sub.4.
[0061] In addition, the compound of formula (I) contains at least
one nitro group.
[0062] In a preferred compound of formula (I), R.sup.1 is H, X is
O, and R.sup.2 is nitro, such that the compound is a salt of the
N-hydroxyl-N'-nitrourea monoanion and a cation Z.sup.m+, having the
structure of formula (Ia)
##STR00007##
[0063] In a particularly preferred embodiment, m and n are 1, and Z
is ammonium, such that the compound is the ammonium salt of the
N-hydroxyl-N'-nitrourea monoanion.
[0064] In another embodiment, the invention provides a salt having
the structure of formula (II)
##STR00008##
wherein R.sup.1, R.sup.2 and X are as defined for formula (I), and
M is an alkali metal such as sodium or potassium. Most preferably,
M is sodium.
[0065] In a preferred compound of formula (II), R.sup.1 is H, X is
O, and R.sup.2 is nitro, such that the compound is a salt of the
N-hydroxyl-N'-nitrourea dianion and a cation M.sup.+, having the
structure of formula (Ia)
##STR00009##
[0066] In a particularly preferred embodiment, M is sodium, and the
compound is the disodium salt of the N-hydroxyl-N'-nitrourea
dianion.
[0067] In another embodiment, the invention is directed to
N-hydroxyl-N'-nitrourea, as a new composition of matter, in
electronically neutral form. The compound has the structure of
formula (III)
##STR00010##
[0068] In another embodiment, the invention is directed to
N-hydroxyl-N-nitroguanidine, in electronically neutral form, also
as a new composition of matter. The compound has the structure of
formula (IV)
##STR00011##
[0069] Energetic compositions of the invention contain a compound
of the invention as provided herein, a binder, and, optionally, one
or more additional energetic materials. The binder will typically
be an organic polymeric material, and may be either inert or
energetic. Generally, the invention polymeric binder represents in
the range of approximately 5 wt. % to 50 wt. % of the composition,
preferably 10 wt. % to 30 wt. % of the composition, while the
energetic material(s) represent approximately 50 wt. to 95 wt. % of
the composition, preferably 70 wt. % to 90 wt. % of the
composition, with one or more compounds of the invention
representing 50 wt. % to 100 wt. %, preferably 75 wt. % to 100 wt.
%, of the total energetic materials in the composition.
[0070] Examples of inert binders include, without limitation:
poly(alkylene glycols) such as polyethylene glycol (PEG) and
poly(ethylene-co-propylene) glycol; polybutadienes such as
hydroxy-terminated polybutadiene (HTPB) and butadiene
acrylonitrile-acrylic acid terpolymer (PBAN); polyesters;
polyacrylates; polymethacrylates; polycarbonates; and
polyurethanes. Examples of energetic polymeric binder materials for
use in propellant applications include, but are not limited to:
polyoxetanes such as nitratomethyl-methyloxetane (poly-NMMO),
poly(bisazidomethyl-oxetane) (poly-BAMO),
poly(azidomethyl-methyloxetane)(poly-AMMO),
poly(nitraminomethyl-methyloxetane) (poly-NAMMO), poly
(BAMO-co-NMMO), and poly(BAMO-co-AMMO); polyglycidyl azide (GAP);
and polyglycidyl nitrate (PGN). Other suitable binder materials
will be known to those skilled in the art and are described in the
pertinent literature.
[0071] It will also be appreciated that the energetic compositions
may also include one or more plasticizers for the polymeric binder.
The plasticizer selected will depend on the particular binder
polymer(s) and on the desired or necessary properties of the
energetic composition. In general, however, plasticizers used in
conjunction with the above-mentioned binders include
dioctyladipate, isodecylperlargonate, dioctylphthalate,
dioctylmaleate, and dibutylphthalate, as well as the energetic
plasticizers
bis(2,2-dinitropropyl)acetal/bis(2,2-dinitropropyl)formal
(BDNPF/BDNPA), trimethylolethanetrinitrate (TMETN),
butanetrioltrinitrate (BTTN), nitroglycerine (NG),
diethyleneglycoldinitrate (DEGN), and triethyleneglycoldinitrate
(TEGDN). Some binders will also require curing agents, such as
isocyanates or the like (e.g., hexamethylene diisocyanate).
[0072] Additional energetic materials that may be incorporated into
the present energetic compositions include conventional explosive
materials such as TNT (2,4,6-trinitrotoluene), RDX
(cyclo-1,3,5-tri-methylene-2,4,6-trinitramine; also referred to as
cyclonite), HMX (1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane),
CL-20
(2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.0..sup.5,9-
.0.sup.3,11]-dodecane), TEX
(4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo[5.5.0.0..sup.5,9.0.s-
up.3,11]-dodecane), NTO (3-nitro-1,2,4-triazol-5-one), TATB
(1,3,5-triamino-2,4,6-trinitrobenzene), TNAZ
(1,3,3-trinitroazetidine), NQ (nitroguanidine), DADNE
(1,1-diamino-2,2-dinitroethane), and picric acid.
[0073] Depending on intended use, the energetic compositions of the
invention will contain additional components, such as a fuel, an
igniter compound (or "initiator"), additional oxidizers, and the
like.
[0074] For example, castable and extrudable explosive formulations
will contain a reactive metal as a fuel, e.g., e.g., aluminum,
beryllium, boron, magnesium, titanium, zirconium, or mixtures or
alloys thereof, and one or more oxidizers in addition to the
inventive compound.
[0075] Preferred igniter compounds for use herein are thermally
stable, typically up to a temperature of at least about 150.degree.
C.; the compounds should also have a relatively high heat of
formation, and be safe, economical, and straightforward to
synthesize in relatively high yield. Conventional igniters such as
lead azide and lead styphnate may be used, although preferred
igniters are the N,N'-azobis-nitroazoles described in commonly
assigned U.S. Pat. No. 5,889,161 to Bottaro et al. for
"N,N-Azobis-Nitroazoles and Analogs Thereof as Igniter Compounds
for Use in Energetic Compositions," assigned to SRI International
(Menlo Park, Calif.).
[0076] Examples of additional oxidizers that may be incorporated
into the energetic compositions include, but are not limited to,
ammonium nitrate (AN), phase-stabilized ammonium nitrate (PSAN),
ammonium dinitramide (ADN), potassium nitrate (KN), potassium
dinitramide (KDN), sodium peroxide (Na.sub.2O.sub.2), ammonium
perchlorate (AP), hydroxylammonium nitrate (HAN), and KDN-AN, a
cocrystallized form of potassium dinitramide and ammonium
nitrate.
[0077] A particular application of such energetic materials is in
the manufacture of propellants, e.g., rocket propellants, including
both solid and solution propellants. That is, such compositions
will contain, in addition to a secondary explosive comprising a
compound of the invention and an igniter material as described
above, an inert or energetic binder, and a metallic fuel. Other
components for incorporation into propellants include burn rate
modifiers, ballistic additives, and the like.
[0078] A compound of the invention may also be used as the liquid
oxidizer component of monopropellant, bipropellant and
tripropellant compositions, without need for additional oxidizing
agents. In addition, the compounds are useful in pyrotechnic
applications, in firearms, and the like.
[0079] Another application of the present compounds is in
gas-generating compositions for inflating airbags in automobiles,
planes, and the like. These gas-generating compositions contain a
compound of the invention, an igniter material as described above,
and, optionally, an additional oxidizer such as AN, PSAN, ADN, KN,
KDN, Na.sub.2O.sub.2, AP, HAN, or KDN-AN. Gas-generating
compositions may also, if desired, contain a gas-generating fuel
and a binder, either an inert or an energetic binder as described
previously. Suitable gas-generating fuels are nitrogenous
compounds, including, by way of example, triaminoguanidine nitrate
(TAGN), diaminoguanidine nitrate (DAGN), monoaminoguanidine nitrate
(MAGN), 3-nitro-1,2,4-triazole-5-one (NTO), salts of NTO, urazole,
triazoles, tetrazoles, guanidine nitrate, oxamide,
oxalyldihydrazide, melamine, various pyrimidines, semicarbazide
(H.sub.2N--(CO)--NHNH.sub.2), azodicarbonamide
(H.sub.2N--(CO)--N.dbd.N--(CO)--NH.sub.2), and mixtures
thereof.
[0080] The compounds of the invention may be readily synthesized in
a variety of ways using techniques that are straightforward and
readily scaled up. Compounds of formulae (I), (II) and (III) may
conveniently be synthesized from a lower alkyl carbamate such as
methyl carbamate, which is available from Aldrich (Milwaukee, Wis.)
and other commercial sources. The carbamate can be treated with
equivalent molar amounts of acetyl nitrate and acetic acid to form
a lower alkyl nitrocarbamate, e.g., methyl nitrocarbamate (for
example by using the procedure described in Example 1 below), or
ethyl nitrocarbamate (also known as nitrourethane). Ethyl
nitrocarbamate can also be obtained commercially, e.g., from
Aldrich. Compounds of formula (I) may then be synthesized by
treating the lower alkyl nitrocarbamate with a hydroxide-releasing
base (e.g., sodium hydroxide or potassium hydroxide) in the
presence of aqueous hydroxylamine until a salt of di-anionic
N-hydroxyl-N'-nitrourea or an analog thereof precipitates (e.g.,
the sodium or potassium salt). The salt may, if desired, be
converted to electronically neutral form (e.g., to provide a
compound of formula (III)), by processing the precipitate (which
may or may not be isolated) with a solution of a strong inorganic
acid, e.g., a sulfuric acid solution. The compound thus
obtained--i.e., NHNU or an analog thereof--may then be obtained by
filtration, and the isolated filtrate then dissolved in a solvent,
e.g. acetonitrile, and crystallized.
[0081] The ammonium salts of NHNU and NHNU analogs may be formed by
direct reaction of NHNU with ammonia, for example, by adding
ammonia to a methanol solution of NHNU in a sufficient amount to
neutralize the solution. The resulting precipitated ammonium salt
of the NHNU monoanion, a compound of formula (II), may then be
filtered and dried.
[0082] The compound of formula (IV), N-hydroxyl-N'-nitroguanidine,
may be synthesized by reacting thiourea with dimethyl sulfate to
provide the sulfate salt of 2-methyl-isothiourea, followed by
nitration with a mixture of nitric acid and sulfuric acid. The
resulting intermediate, N-nitro-2-methyl-isothiourea, is then
converted to N-hydroxyl-N'-nitroguanidine with hydroxylamine and
precipitated from ethanol. The reaction is illustrated in Scheme
1:
##STR00012##
[0083] Alternatively, the compound of formula (IV),
N-hydroxyl-N'-nitroguanidine, may be directly synthesized from
N-nitroguanidine as indicated in Scheme 2:
##STR00013##
[0084] Synthetic details not explicitly disclosed herein are within
the knowledge of or may be deduced by one skilled in the art of
synthetic organic chemistry, or may be found in, e.g.,
Kirk-Othmer's Encyclopedia of Chemical Technology, House's Modern
Synthetic Reactions, C. S. Marvel and G. S. Hiers' text, ORGANIC
SYNTHESIS, Collective Volume 1, or in T. L. Gilchrist, Heterocyclic
Chemistry, 2nd Ed. (New York: John Wiley & Sons, 1992), or the
like. Synthesis of representative compounds is exemplified
below
[0085] Manufacture of gas-generating compositions, propellants, and
other energetic compositions may be carried out using conventional
means, as will be appreciated by those skilled in the art. A
suitable method for preparing anhydrous gas-generating compositions
is disclosed, for example, in U.S. Pat. No. 5,473,647 to Blau et
al. and in international patent publication WO 95/00462 (Poole et
al.).
[0086] Of course, other methods for manufacture may be used as
well. Such methods are described in the pertinent literature or
will be known to those familiar with the preparation of energetic
compositions.
[0087] It is to be understood that while the invention has been
described in conjunction with the preferred specific embodiments
thereof, the description above as well as the examples that follow
are intended to illustrate and not limit the scope of the
invention. Other aspects, advantages, and modifications within the
scope of the invention will be apparent to those skilled in the art
to which the invention pertains.
[0088] All patents, patent applications, journal articles, and
other reference cited herein are incorporated by reference in their
entireties.
EXPERIMENTAL
[0089] 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 prepare and use the 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 degrees
Celsius (C), and pressure is at or near atmospheric.
Example 1
Synthesis of N-Hydroxyl-N'-Nitrourea, Dipotassium Salt
[0090] (a) Preparation of methyl nitrocarbamate: Methyl carbamate
(0.5 mole) (obtained from Aldrich) was dissolved in 500 mL of
CHCl.sub.3 and cooled to 0.degree. C. This mixture was treated with
a solution of 0.5 mole acetyl nitrate, 0.5 mole acetic acid, and
200 mL chloroform over 1 hour. The mixture was allowed to warm
overnight and was concentrated in vacuo, drying under high
vacuum.
[0091] (b) Methyl nitrocarbamate (100 mmol) was dissolved in 80 mL
of methanol and cooled to 0.degree. C. A solution of 100 mmol
potassium hydroxide in 20 mL of methanol was added with stirring
(forming potassium methyl nitrocarbamate). Next, a solution of 100
mmol of potassium hydroxide, 120 mmol of hydroxylamine, and 50 mL
of methanol was added, with stirring. A dense, yellow precipitate
appeared, which was the di-anion of N-hydroxyl-N'-nitrourea (NHNU),
as its potassium salt.
Example 2
Synthesis of N-Hydroxyl-N'-Nitrourea
[0092] The reaction mixture containing the NHNU dipotassium salt
obtained in part (b) of Example 1 was stirred for 3 hours at
0.degree. C., and then neutralized with 110 mmol of
H.sub.2SO.sub.4, mixed with 500 mL 2-propanol, filtered, and the
filtrate concentrated to dryness. The crude residue was
crystallized from 500 mL hot acetonitrile to give 8.0 g of NHNU in
the form of orthorhombic prisms. The crystals were found to
decompose at about 145.degree. C.
[0093] Differential scanning calorimetry (DSC) was performed on the
obtained NHNU using a TA Instruments DSC, scanned from 30.degree.
C. to 250.degree. C. at 10.degree. C. per minute on a sample
weighing 0.200 mg. A single, very strong exothermic peak was
produced, at about 156.5.degree. C. The area under this peak
indicated an energy content of about 2445 J/g.
[0094] The crystal structure of the obtained NHNU was determined by
x-ray crystallography at 293(2) K. A single crystal of NHNU, about
0.40.times.0.18.times.0.23 mm.sup.3, was used for the analysis. The
crystal was determined to be orthorhombic, space group
P2.sub.12.sub.12.sub.1 (no. 19), unit cell dimensions a=4.7116(4)
.ANG., b=6.9585(6) .ANG., c=12.8495(11) .ANG. (where the numbers in
parentheses are the estimated standard deviations for the least
significant digits). There are four formula units of
CH.sub.3N.sub.3O.sub.4 in the unit cell, leading to a calculated
density of about 1.91 g/cm.sup.3. The determined structure of the
NHNU molecule is shown in FIG. 1, and the crystal structure is
shown in FIG. 2. It is noted that different crystal structures may
be obtained under different conditions of crystal growth.
Example 3
Evaluation of N-Hydroxyl-N'-Nitrourea
[0095] Various properties of NHNU (in electronically neutral form)
were evaluated using standard equipment and procedures, and the
results are set forth in Table 1:
TABLE-US-00001 TABLE 1 PROPERTY EVALUATED RESULT Density 1.909 g/cc
(x-ray diffraction) ABL Impact 11 cm ABL Friction 50 lb @ 8 ft/sec
TC Impact 19.5 cm (H.sub.50) (1 kg drop weight test) TC ESD
Unconfined >8 Joules SBAT Onset 193.degree. F. exotherm Iso SBAT
@ 225.degree. F., immediate exotherm >30.degree. F.
Example 4
Synthesis of N-Hydroxyl-N'-Nitrourea, Ammonium Salt
[0096] The ammonium salt of NHNU was synthesized as follows:
N-hydroxyl-N'-nitrourea (16 mmol) was dissolved in 25 mL of
methanol at 20.degree. C. One equivalent of ammonia (0.5 M in
1,4-dioxane) was added, and a precipitate appeared immediately.
After 20 minutes of stirring the solid was isolated by filtration,
washed with 10 mL methanol, and air dried to give 2.0 g of ammonium
N-hydroxyl-N'-nitrourea. The salt was slightly soluble in hot
methanol (about 0.3 g in 100 mL of methanol).
[0097] Differential scanning calorimetry (DSC) was performed on the
obtained ammonium-NHNU using a TA Instruments DSC, scanned from
30.degree. C. to 220.degree. C. at 10.degree. C. per minute on a
sample weighing 0.200 mg. A single, very strong exothermic peak was
produced, at about 157.degree. C. The area under this peak
indicated an energy content of about 1541 J/g.
[0098] The crystal structure of the obtained ammonium salt of NHNU
was determined by x-ray crystallography at 293(2) K. A single
crystal of this salt, about 0.24.times.0.14.times.0.04 mm.sup.3,
was used for the analysis. The crystal was determined to be
triclinic, space group P-1 (no. 2), unit cell dimensions
a=5.3765(4) .ANG., b=6.7723(5) .ANG., c=7.9155(5) .ANG.,
.alpha.=109.873(4).degree., .beta.=100.217(4).degree.,
.gamma.=102.520(4).degree.. There are two formula units of
CH.sub.6N.sub.4O.sub.4 in the unit cell, leading to a calculated
density of about 1.80 g/cm.sup.3. The determined structure of the
ammonia salt of the NHNU molecule is shown in FIG. 3, and the unit
cell contents are shown in FIG. 4. It is noted that different
crystal structures may be obtained under different conditions of
crystal growth.
Example 5
Synthesis of N-Hydroxyl-N'-Nitroguanidine
[0099] The compound of formula (IV), N-hydroxyl-N'-nitroguanidine,
was synthesized by reacting thiourea with dimethyl sulfate to
provide the sulfate salt of 2-methyl-isothiourea, followed by
nitration with a mixture of nitric acid and sulfuric acid (as
described in the Journal of the American Chemical Society 76 :1877
(1954). The resulting intermediate, N-nitro-2-methyl-isothiourea
(37 mmol) was combined with 37 mmol of hydroxylamine in 75 mL of
ethanol. After stirring for 4 hours the precipitate was isolated by
filtration, washed with 20 mL of ethanol and air-dried to give
N-hydroxyl-N'-nitroguanidine in 85% yield.
[0100] Differential scanning calorimetry (DSC) was performed on the
obtained compound using a TA Instruments DSC, scanned from
30.degree. C. to 220.degree. C. at 10.degree. C. per minute on a
sample weighing 0.210 mg. A single, very strong exothermic peak was
produced, at about 114.degree. C. The area under this peak
indicated an energy content of about 1873 J/g.
[0101] The crystal structure of the compound was determined by
x-ray crystallography at 293(2) K. A single crystal of this salt,
about 0.08.times.0.08.times.0.24 mm.sup.3, was used for the
analysis. The crystal was determined to be monoclinic, space group
C2/c, unit cell dimensions a=17.9449(2) .ANG., b=4.22690(10) .ANG.,
c=11.89120(10) .ANG., .alpha.=90.degree.,
.beta.=99.9270(10).degree., .gamma.=90.degree.. Calculated density:
1.795 g/cm.sup.3. The determined structure of the compound is shown
in FIG. 5.
Example 6
Preparation and Testing of Propellant Compositions
[0102] NHNU was mixed with several combinations of propellant
components, as indicated in Table 1. Each of these mixtures was
placed in a differential scanning calorimeter (DSC) and held at
80.degree. C. for 24 h. The times and magnitudes of any resulting
exotherms or endotherms were recorded and shown in Table 2. Unless
otherwise indicated, the typical first exotherm was a somewhat
broad but large peak, taking about three hours to fully develop,
which was followed by a sharp spike about 15 minutes in duration.
The largest exotherms, representing the largest energy releases,
generally occurred when NHNU was mixed with ammonium nitrate
(AN).
[0103] NHNU was mixed with several combinations of potential
propellant components, as indicated in Table 1. Each of these
mixtures was placed in a differential scanning calorimeter (DSC)
and held at 80.degree. C. for 24 h. The times and magnitudes of any
resulting exotherms or endotherms were recorded, as shown in Table
2. Unless otherwise indicated, the typical first exotherm was a
somewhat broad but large peak, taking about three hours to fully
develop, which was followed by a sharp spike about 15 minutes in
duration. The largest exotherms, representing the largest energy
releases, generally occurred when NHNU was mixed with ammonium
nitrate (AN).
TABLE-US-00002 TABLE 2 Thermal behavior of NHNU in combination with
other materials at 80.degree. C.: MIXTURE TIME TO EXOTHERM(S) NHNU,
PGN, BTTN 16 h, 17 h NHNU, BTTN, AN 7 h, 9 h; endotherm at 5 h
NHNU, PGN, AN 4 h, 5.5 h, 7.25 h; endotherm at 4.25 h NHNU, PGN,
ADN Jagged base line; no definite exotherm NHNU, PGN, CL-20 15 h,
16 h NHNU, PGN, N-100 No exotherm; endotherm at 3.25 h NHNU, BTTN,
ADN Jagged base line; slow exotherm at 14 h NHNU, BTTN, CL-20
Slight at 2 h, 6 h NHNU, BTTN, N-100 Slow, slight at 7 h, 8.5 h
NHNU, AN, ADN 2 h, 5 h NHNU, AN, CL-20 5 h, 7 h; endotherm at 3.5 h
NHNU, AN, N-100 No exotherm; endotherms at 2.5 h, 9 h NHNU, ADN,
CL-20 Slow, mild at 14 h; mild at 16 h NHNU, ADN, N-100 No
exotherm; endotherms at 2 h, 9 h NHNU, CL-20, N-100 No exotherm;
endotherm at 8 h
[0104] In Table 2, the abbreviations used are as follows:
ADN=ammonium dinitramide; AN=ammonium nitrate;
BTTN=butanetrioltrinitrate;
CL-20=2,4,6,8,10,12-hexanitrohexaaza-isowurtzitane; N-100=aliphatic
polyisocyanate resin based on hexamethylene diisocyanate, available
from Bayer Corporation, Pittsburgh, Pa. as Desmodur.RTM. N100;
NHNU=N-hydroxyl-N'-nitrourea; PGN=polyglycidylnitrate.
* * * * *