Organic compounds -- part of the class 532-570 series – Organic compounds – Unsubstituted hydrocarbyl chain between the ring and the -c-...
Reexamination Certificate
2000-06-08
2003-01-28
Coleman, Brenda (Department: 1624)
Organic compounds -- part of the class 532-570 series
Organic compounds
Unsubstituted hydrocarbyl chain between the ring and the -c-...
C149S092000
Reexamination Certificate
active
06512113
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process of making the low sensitivity, high energy density solid oxidizer 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo[5.5.0.0
5,9
0
3,11
]-dodecane, also known as “TEX”. The process provides several advantages over known processes, including faster reaction times with excellent yields and product purity.
2. Description of the Related Art
A synthesis route for preparing TEX is disclosed in U.S. Pat. No. 5,498,711, the complete disclosure of which is incorporated herein by reference. According to the '711 patent, TEX is synthesized by reacting 1,4-diformyl-2,3,5,6-tetrahydroxypiperazine and derivatives thereof with a strong acid and a nitrate source at temperatures greater than ambient temperature, such as temperatures in a range of 50° C. to 70° C. The strong acid and nitrate source of preference are sulfuric acid and nitric acid, respectively. The reaction is exothermic and is allowed to continue for two to three hours. The mixture is then poured onto ice, and a solid precipitate is isolated and washed to give a mixture which contains the TEX. The reaction is shown below:
Purification can then be accomplished by heating the reaction product in nitric acid, washing with methanol, and/or washing with a base to neutralize excess acid. The pure product may be obtained by recrystallization according to standard procedures.
The synthesis route reported in the '711 patent produces TEX in yields and purities that constitute improvements over the known art. However, as is evident from the relatively long reaction times of 2 to 3 hours and the use of NO
x
scavengers, the '711 patent teaches not terminating the reaction until after TEX is precipitated out and NO
x
by-product gases are generated. The generation of NO
x
gases, such as NO
2
, is an autocatalyzing reaction that becomes rapid within a relatively brief period of time, with the actual period depending on various factors, such as piperazine derivative concentration and make-up of the acid bath. Rapid generation of NO
x
causes fume off of reactants and product, which lowers product yield and makes the process less conducive to applications in large-scale TEX production operations.
SUMMARY OF THE INVENTION
It is, therefore, an object of this invention to address a need in the art by providing a method by which 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo[5.5.0.0
5,9
0
3,11
]-dodecane (herein referred to as TEX) can be synthesized at a sufficiently high purity and yield to permit its large scale production in an economically feasible manner.
In accordance with the objects of this invention, these and other objects are accomplished by the provision of process in which TEX is prepared by reacting at least one suitable hexa-substituted piperazine derivative (preferably 1,4-diformyl-2,3,5,6-tetrahydroxypiperazine and/or a derivative thereof) in a medium comprising at least one nitrate source and optionally at least one strong acid at temperatures equal to or greater than ambient temperature, with the reaction temperature preferably being in the range of from about 50° C. to about 80° C. During the initial stages of the reaction, which are highly exothermic, the temperature of the medium is maintained in a range of from about 50° C. to about 80° C. using cooling techniques. Subsequently, the initial exotherm ceases or substantially abates, at which point cooling can be terminated while still maintaining the reaction temperature in the range of from about 50° C. to about 80° C. Eventually, NO
x
generation commences via an exothermic autocatalytic reaction. Although the inventors do not wish to be bound by any theory, it is believed that the autocatalytic reaction is dependent upon there being a predetermined amount of water present in the medium. The reaction is stopped by cooling the medium to a temperature sufficiently low either to prevent onset of the NO
x
autocatalytic stage or, if the NO
x
autocatalytic stage has already commenced prior to the final cooling step, to terminate the autocatalytic generation of NO
x
. Preferably, the autocatalytic generation of NO
x
is terminated before a sufficient exotherm has been released to permit the medium (while not being cooled) to be raised in temperature by more than 5° C. The reaction product is precipitated in a conventional manner, preferably by cooling at room temperature, and purified to yield TEX.
Advantageously, because the heat source is removed prior to or just after the formation of NO
x
, the rapid release and fume off of NO
2
is avoided. Furthermore, unlike many conventional processes, a NO
x
scavenger, such as urea, may be omitted from the reaction to reduce the likelihood of by-product forming reactions. Moreover, unlike conventional processes, in a preferred embodiment the present invention is conducted in a medium which is free or substantially free of a strong acid other than nitric acid. Counter-intuitively, it has been found that the elimination of a strong acid, such as sulfuric acid, increases the TEX formation rate.
The present process can be conducted on a large manufacturing scale in which the exothermic reaction process is controllable, while directly yielding greater amounts of TEX in a high purity sufficient for use in formulating explosive compositions. These advantages are obtainable without requiring the heretofore extensive further purification or recrystallization steps.
Other objects, aspects and advantages of the invention will be apparent to those skilled in the art upon reading the specification and appended claims, which explain the principles of this invention.
DETAILED DESCRIPTION OF THE INVENTION
In the present process, TEX is prepared by addition of a predried mixture of a hexa-substituted piperazine derivative to a heated acid medium comprising at least one nitrate source and, optionally, at least one strong acid.
Hexa-substituted piperazine derivatives suitable for use in the present process are represented by the following general formula (1):
wherein —OR is a good leaving group and R is H, R″, —CR″O, —COR″, —COOR″, —SO
3
R″, —NO, —NO
2
, acetal (including aliphatic (e.g., formal), cycloaliphatic (e.g., cyclohexanal), and branched acetals (e.g., dimethylketal)), and cycloacetals; R′ is a nitrolyzable group such as —CR″O, —COR″, —SO
2
R″, —SO
3
M, —NO
2
, —NO, —COOR″, t-butyl, cyclohexyl, and isopropyl; M is an alkali metal, preferably lithium, sodium, or potassium; R″ is H, C
1
to C
10
alkyl, branched alkyl, cycloalkyl, and aryl (such as phenyl and substituted phenyl) and monocyclic heterocyclic moieties, and wherein each R, R′, or R″ can independently be the same or different. As used herein, phenyl substituents include, but are not limited to, C
1
to C
10
alkyl, branched alkyl, halogen, nitro, amino, substituted amino, alkoxy, acyl, and carbonyl containing moieties such as carboxyl, ester, ketone, etc. Exemplary, suitable monocyclic heterocyclic moieties contain one or more heteroatoms such as nitrogen, sulfur, and/or oxygen (e.g., triazinethiophenefuran). Representative hexa-substituted piperazine derivatives include, for example,1,4-bis(methylsulphonyl)-2,3,5,6-tetrahydroxypiperazine, disodium-2,3,5,6-tetrahydroxypiperazine-1,4-disulphonate, 1,4-diformyl-2,3,5,6-tetraacetoxypiperazine, and, 1,4-diformyl-2,3,5,6-tetrahydroxypiperazine (THDFP). Of the above hexa-substituted piperazine derivatives, THDFP is the preferred starting material. THDFP is illustrated below by the following formula (2):
Typical hexa-substituted piperazine derivatives which may be used to synthesize TEX can be prepared by reacting glyoxal with an amide, sulfonamide, or sulfonate salt in known methods. Other hexa-substituted piperazine derivatives which may be used in the present invention are reported in Currie, A. C., et al., “Base-catalysed Reactions of Glyoxal. Part I. 1,4-Diformyl- and 1,4-Bismethylsulphonyl-Derivatives of 2,3,5,6-tetrahydroxypi
Hajik Robert M.
Highsmith Thomas K.
Johnston Harold E.
Sanderson Andrew J.
Alliant Techsystems Inc.
Coleman Brenda
Sullivan Law Group
LandOfFree
Synthesis for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Synthesis for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Synthesis for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3000771