US3390183A - Preparation of nitramines - Google Patents

Description

United States Patent Ofioce 3,390,183 Patented J une 25, 1968 3,390,183 PREPARATION OF NITRAMINES Milton B. Frankel, Menlo Park, and Karl Klager, Sacramento, Calif., assignors to Aerojet-General Corporation, Azusa, Calif., a corporation of Ohio No Drawing. Original application June 8, 1964, Ser. No. 374,235. Divided and this application Dec. 27, 1966, Ser. No. 620,200

6 Claims. (Cl. 260-583) This is a division of application Ser. No. 374,235, filed June 8, 1964.

This invention relates to novel nitramides and to the conversion of the nitramides to nitramines.

The primary nitramines are a class of compounds having a wide variety of uses, particularly in rocket propellants and explosives. The energy provided by these compounds in a propellant or explosive composition is dependent to a considerable extent on the nitramine being present in essentially pure form. If the nitramine component in the composition is contaminated or diluted with impurities or by-products from the synthesis reactions, the overall effectiveness of the propellant or explosive is reduced. Previously attempts have been made to prepare primary nitramines by direct nitration of the free amine, or by dehydration of the nitrate salt. However, it has been found that primary nitramines, such as 3,6-dinitraza- 1,8-octane dinitramine, cannot be prepared in good yield by direct nitration of the corresponding amine or by dehydration of the nitrate salts of the corresponding primary amine because both of these techniques involve the contacting of the primary nitramine, as it is formed, with strong acid which causes excessive decomposition of the desired product. This decomposition which occurs in the prior art processes yields the primary nitramine in very impure form, making the compounds generally unsuitable ,for direct use in propellants and explosives. Removal of these contaminants involves many involved and costly purification procedures.

It has now been found that primary nitramines can be prepared from novel nitramides in good yield and without the need for contacting the primary nitramine with a strong acid. The primary nitramines of our invention are directly obtained in high purity, thus avoiding elaborate after-treatment and purification. According to'our invention, the primary nitramines are obtained by preparing a nitramide by reaction of the corresponding amide with an ionic nitrating agent, followed by hydrolysis. This novel technique will be more fully understood, in both its broad and specific aspects, from the discussion which follows. It can be seen, however, that by the practice of our invention, the contact of the ionic nitrating agent with the free primary amine is altogether eliminated.

It is an object of this invention to prepare primary nitramines without contacting the primary nitramine with strong acid. It is still a further object of this invention to prepare nitramines by a method which will provide these compounds in better yield and greater purity than those methods previously known. Still another object of this invention is to prepare novel nitramides. These and other objects of this invention will be apparent from the description which follows.

One of the starting materials in the preparation of the primary nitramines, according to the method of this invention, are the nitramides having the following general formula:

wherein A and A are alkylene radicals, preferably lower radical wherein R is as has already been defined.

The nitramides of the above formula are prepared by reacting (Reaction I) an ionic nitratingagent with a compound of the formula:

wherein A, A, R, R and n are as defined above. In the above reaction, the choice of the ionic nitrating agent is not critical. Any of the common strong ionic nitrating agents such as nitric acid, mixtures of nitric acid and-sulfuric acid, mixtures of nitric acid and acetic anhydride, and mixtures of methyl nitrate and sulfuric acid may be used. Ionic nitrating agents containing nitric acid are preferred.

Generally speaking, a solvent is not required in order to prepare the novel amides of our invention, according to Reaction I. However, if desired, any essentially inert solvent can be used, although carbon tetrachloride is preferred. The proportions of the nitramine and ionic nitrating agent employed in the above reaction are not critical. Preferably the ionic nitrating agent is used in an amount stoichiometrically in excess to the amount of the nitramide employed so as to drive the reaction to completion within a reasonable length of time. The reaction temperature may be varied over a wide range. The preferred range is from about l5 C. to about +35 C.

The novel nitramides prepared in the above manner are converted to the nitramines by hydrolyzing the nitramides in accordance with the general reaction (Reaction II) set forth below.

amides undergo hydrolysis under basic conditions, such as by the addition of sodium hydroxide, potassium hydroxide, ammonium hydroxide, and the like, to the amide. Optimum results were obtained when the hydrolysis was conducted in an ammoniacal media. It is to be understood that hydrolysis of the amide with base yields the amine in the form of the basic salt. The free amine is then obtained by neutralizing the salt with a stoichiometn'c equivalent amount of an acid such as hydrochloric acid. In Reaction II, the reactants are ideally used in stoichiometrically equivalent amounts since this results in the most complete utilization of the reactants. However,

the proportions may be varied'over-a-wide range without adversely affecting the reaction.

The preparation of the nitramine is preferably carried "outbyfadditionfof the base'to the nitramide.-No solvents are ordinarilyneces'sary; However, if desired, a polar solvent-such aswater'may be -used."---:: Y f"- Itis desirable that'xth'e hydrolysis=-of the'nitramide be carried out at temperature between about 0 C. and ai io't'1t' 100"" (3., althou' h this reaction range is not critical to our 'invention. 11 Pressure '*n'otcritical in--the "preparation of the hitramid'e or the nitrami'ne'; Therefore thereactions may be run at any pressure, atmospheric pressure being most convenient.

The nitramides and nitramines of this invention are normally solids and may be isolated in conventional manner by filtration, evaporation and/ or crystallization.

To more clearly illustrate our invention, the following examples are: presentedlt is to be understood, however, that, these examples; are intended merely as illustrative embodiments of the. invention and should not be construed as being limitative of the scope of said invention in any way. In the examples percentages are by weight unless otherwise indicated.

Example I.--Prepar'ation of N,N'-dinitro-3,6-dinitrazaoctamethylene-bis-acetamide To a 500 ml. flask, fitted with a mechanical stirrer, thermometer and dropping funnel, was added 150 ml. of acetic anhydride. Keeping the temperature of the mixture at 0 C. to 5 C., 150ml. of 100 percent nitric acid was added dropwise, and then*17.5' grams of 3,6dinitrazaoctamethylene bis-acetamide was added: The reaction mixture was stirred for 45 minutes at 0 C. to 5 C. and poured mice. The white solid which formed was collected, washed with water and dried in vacuo over potassium hydroxide. Recrystallization from ethylene dichloride gave 12.5 grams' (55.8 percent) of N,N'-dinitro-3,6

dinitraza-octamethylene-bis-acetamide, having a melting -point of 127? C. to 128 C. The elemental analysis of the product is as follows: 1

Calcd for C H N O percent: C, 29.27; H, 4.42; N, 27.31. Found, percent: C,-29.00; H, 4.25; N, 27.21. The 3,6- dinitraza-octamethylene bis-acetamide employed in the above example is prepared by the reaction of sodium inethoxide and acetic anhydride with 3,6-di- 'nitr'aza-1,8-octane diamine hydrochloride, as is more fully disclosed in U.S. Patent No. 2,967,198, issued Jan. 3, 1961." i

- -Example II.- -Preparation of N,-N'-dinitro-4-nitrazaheptamethylene-bis-caproamide To a flask is added equal volumes of acetic anhydride and 100 percent nitric acid. The temperature is maintained at about 0-10" C. and 4-nitraza-heptamethylen'ebis-caproamide is added to the mixed acids in increments water, and dried,---2l .6 g. {44.5% -68-70 .-'-"Recrystallization from carbomtetrachloride raised the melting point to 7273.

Analysis.-Calcd for C H N O percent: C, 29.82;

H, 4.38. Found, percenttC, 29.93; H, 4.38.

V To 6.5 grams" f N,N'-dinitro 3,6-diriitraza-octamethyl eiie-bi's-acetamide (pi epaired ace'ordingtoExainple I) was added 25 ml. of 28"percent ammonium hydroxide' 'I'he solid dissolved with the evolutionofheat. The solution was cooled in an ice bath and acidified with dilute hydrochloric acid; The white solid which precipitated, was collected, washed with water, and dried in vacuo over potassium hydroxide. Recrystallization from. acetonechloroform gave- 5.1 grams (98.7%, based on the amide) of '3,6-,d initr aza-1,8-octane -dinitramine. in the form of .white needles, having amelting point of 177-1'7 8".C. The elemental analysis of the product is as follows:

.iCalcdfor C l-1 N 0 percent: .C, 22.09; -H, 4.33; N, 34.35. Found, percent: C,'22.33; H,.4.28; N, 34.14. Example V. Prep'a'ration of' 4-nitraza-l,7-

, heptan'e dinitramine To N,N-dinitr0-4 nitraza heptamethylene-bis-caproamide (prepared as inExample II) is added an equivalent amount of 28 percent ammonium hydroxide. The solid is allowed to dissolve and is then acidified with dilute hydrochloric acid. -The solid precipitate is .collected, washed and dried to -give 4nitraza?1,7-heptane dinitramine in goodyield. V

1 Example VI.Preparation of 3-nitraza-l,5-pentane 'dinitramine a To 21.6. g. 10.067, mole) of N,N'- dinitro- 3-nitraza-per t tane-bis-acetar'nide was added ml. of water and 50 ml.

of concentrated ammonium hydroxide solution. The additionof the base caused thesolid to dissolve with the evolution of heat. The solution was warmed on the steambath for five minutes,,.cooled, and acidified with dilute hydrochloric acid. The white solid which precipitated was collected, washed with water,-and dried, 15.0 g. (94%),

cording to the above examples. For example, 4.7-diniuntil the total diamine added is about stoichiometrically equivalent to the amount of nitrating agent present. The mixture is agitated while being maintained at about 5- 10 C. and then poured on ice. Recrystallization of the product in accordance with the procedure of Example I yields N,Nedinitro-4-nitraza-heptamethylene-bis-caproamide in the form of-ra solid product.

Example llL- -l reparation of N,N'-dinitro-3-nitrazapentane-bis-acetamide In -a one-liter S-necked flask,- fitted with a mechanical 4 at this temperature. To the acid solution was added 35.0

g. (0.15 mole) of 3:nitrazapentane-bis-acetamide. After minutes at '-.-5 to 0" the solid had dissolved. The solution was poured on ice, the white solid collected, washed with traza-decamethylene-bis-butyramide is nitrated with. a solution of methyl nitrate and sulfuricacid to form N,N'- dinitro 4,7-dinitraza-decamethylene-bis=butyramide. This latter compound 'is then reacted sequentially with ammonium hydroxide and hydrochloric acid to form 4,7-dinitraza-l,l0 decane dinitramine. i

In the preparation of the nitramines and nitramides, according to the method of this invention, it is sometimes desirable to agitate the ingredients so as to assure more intimate contact and therebyv an impr'ovedrate of reactron. .I' ,,,The"nitramines and nitramides .of this invention contain a plurality jof nitro groups, and thus are inherently useful as explosives-Thenitramide andnitramine compounds of ourl invention will find utility in solid rocket propellants. More specifically, these compounds maybe used to increase the specific impulse of the knownsolid pgopellants used in intermedi te and intercontinental ballistic missiles,'such as the aluminized polyurethane systerns and those based on carbo'xy-terminated polybutadiene-azirindinyl curative binders.

The novel nitramides as well as the nitramines of this invention can also be. used in any conventional explosive missile or rocket as the .T'main explosive charge. An example of such a missile is disclosed in United States Patent No. 2,470,162, issued May 17, 1949. The'high explosives of this invention can be used in such a device by simply packing the explosive in powdered form into the warhead of the missile.

This application is a continuation-in-part of applicants copending U.S. patent application, Ser. No. 209,276, filed July 9, 1962.

It will be understood that various modifications may be made in this invention without departing from the spirit or the scope of the appended claims.

with an ionic nitrating agent to form the nitramide of the formula:

wherein in each of the above formulae, R and R are lower alkyl radicals, A and A are lower alkylene radicals, and n is a small whole number of from 1 to about 4; hydrolyzing the thus formed nitramide to the nitramine salt by the addition of a base, and neutralizing said salt to the nitramine by the addition of a mineral acid.

2. The method of claim 1 wherein the hydrolysis is followed by the addition of hydrochloric acid.

3. The method of claim 1 wherein the ionic nitrating agent contains nitric acid, and the hydrolysis is carried out by the addition of ammonium hydroxide.

4. The method of preparing 3-nitraza1,5-pentane dinitramine which comprises reacting 3-nitraza-pentane-bisacetamide with nitric acid, followed by hydrolysis with ammonium hydroxide and neutralization With hydrochloric acid to form said dinitramine.

5. The method of preparing 3,6-dinitraza-1,8-octane dinitrarnine which comprises reacting 3,6-dinitraza-octamethylene-bis-acetamide with nitric acid, followed by hydrolysis with ammonium hydroxide and neutralization with hydrochloric acid to form said dinitramine.

6. The method of claim 5 wherein the reaction with the nitric acid is carried out at a temperature of about 0 C. to about +10 C.

References Cited UNITED STATES PATENTS 10/1958 Sauer.

4/ 1961 Frankel et al.

OTHER REFERENCES CHARLES B. PARKER, Primary Examiner.

R. RAYMOND, Assistant Examiner.

Claims (1)

1. THE METHOD OF PREPARING NITRAMINES OF THE FORMULA: