US2678927A

US2678927A - Nitramines and their preparation

Info

Publication number: US2678927A
Application number: US560704A
Authority: US
Inventors: George F Wright; Chute Walter John
Original assignee: HONORARY ADVISORY COUNCIL SCI
Current assignee: HONORARY ADVISORY COUNCIL FOR SCIENTIFIC AND INDUSTRIAL RESEARCH; HONORARY ADVISORY COUNCIL SCI
Priority date: 1944-10-27
Filing date: 1944-10-27
Publication date: 1954-05-18
Anticipated expiration: 1971-05-18

Description

' May 18, 1954 G. F. WRIGHT ETAL NITRAMINES AND THEIR PREPARATION Filed Oct. 27, 1944 Hmm MLZJ Q '3 Mod Bumm lO-N Patented May 18, 1954 UNITED STAT ENT OFFICE NITRAIWINES AND THEIR PREPARATION Application October 27, 1944, Serial No. 560,704

2 Claims.

The present invention relates to a new series of chemical compounds and methods of preparing the same. More particularly the invention is concerned with certain new nitramines and their preparation from readily available raw materials.

Broadly speaking, the object of the present l invention is to provide a new series of polymethylene polynitramines suitable for various industrial purposes but of particular interest in connection with the production of military and industrial explosives.

A more particular object is the provision of a new cyclic polymethylene polynitramine having an eight-membered ring structure, said compound being equal to cyclonite in explosive power and brisance.

Another object is to provide a new and improved explosive of great power and brisance.

A further object is to produce a dinitro derivative of a bicyclic polymethylene polyamine and to convert this intermediate compound to Various derivatives of interest as explosives, fuse powders and the like.

Another object is the provision of a number of alternative methods of preparing said bicyclic intermediate from various readily available raw materials. l E

Still another object is to provide a method of producing an explosive essentially comprising a In view of the close similarity of this new compound (I) to cyclonite (II), both in structure as well as in chemical and explosive properties, the eight-membered cyclic homologue (I) of cyclonite will hereinafter be designated by the trivial name homocyclonite In accordance with one aspect of the present invention, homocyclonite (I) may be prepared by mixture of cyclonite and an analogous, equally powerful polymethylene polynitramine having an eight-membered ring structure.

Other objects and advantages will become apparent as the invention is hereinafter more particularly described.

The subject matter of the present application I (Homocyclonite) II (Cyclonite) amine (IV) a variety of methods from an intermediate that is also a new chemical compound. The intermediate, in turn, may be prepared from readily available raw materials bya number of novel alternative methods to be described later. The intermediate in question consists of 3,7-dinitropentamethylenetetramine (III) (hereinafter reierred to by the trivial designation, DPT) having thel following probable structural formula:

Hz-N-CHz III (DP T) This intermediater (DPT) may be converted either to homocyclonite, or to a mixture of cyclonite and homocyclonite or to certain linear polyntramines that are also of interest in the preparation of explosives of various types.

' The various reactions involved in the preparation of the bicyclic intermediate (DPT), its

conversion to the derivatives briefly mentioned above, and the properties of certain of the products will be hereinafter described with reference to the several plates attached. hereto, wherein:

Plate I is a schematic representation of the reactions involved in the preparation of DPT;

Plate II is a schematic representation of the Y'conversion of DPT to various end products, and

Plate III shown in the accompanying' drawing is a plot of melting points versus composition, of a mixture of 1cyclonite and homocyclonite as produced in accordance with one aspect ot the present invention.

As will be evident by reference to Plate I, DPT (III) may be prepared by neutralization of the mother liquors obtained in the nitrolysis of hex- Alternatively. DPT may be prepared from hexamine dinitrate V) by treatso "ment with a carboxylic anhydride 01' it may be produced synthetically by condensation of formaldehyde, nitramide (VI) and ammonia.

As indicated in Plate II, if the DPT obtained by any of the foregoing processes is treated with absolute nitric acid or with absolute nitric acid, ammonium nitrate and acetic anhydride, a novel explosive homocyclonite is produced, but with a solution of ammonium nitrate in concentrated nitric acid, a mixture of cyclonite (II) and homocycloni'te (I) is produced. Moreover, if DPT is In order more clearly to disclose the nature of the present invention, a number of specific examples will hereinafter be described in considerable detail. It should be clearly understood, however, that this is to be done solely by Way of example and is not to be construed as a limitation upon the spirit and scope of the appended claims.

treated with a mixture of concentrated nitric PLATE 1 acid and acetic anhydride an acetyl-ated linear i PreparatmofDPT polynitramine (VIII) (hereinafter referred to CH2 CHE by the trivial designation AcAn) is formed. v/ T V v Furthermore, if DPT is treated with 106% ni- N\ HNO /N'HNO tric acid (i. e., absolute nitric acid containing l CH) @t CH2 CH2 sufficient dissolved nitrogen pentoxide to titrate N N as apparentlf,7 106% acid), a` linear polynitramine (vin hereinafter designated by the trivial CH, H2 CH, CH, CH2 CH, name 106) is formed. Lastly if 105 is treated lr/ with an alcolici, the nitroxy groups are replaced K l n by alkoxy groups to form the corresponding ether (Hexamme) (Hexamme ummm (IX) which for convenience may be designated Iv v 10G-E.

n 9s o HNOS, t 'Io summarize the foregoing reactions of DPT Zyclonite stllang\ CZO or its derivatives: tralizeMLtepH 51N .z2-4 days 1) DPT+98%rn\Io3- Homeeye1onite (I) (Frei-"CH2 (2) DPT+IINO3+Ac2O|NH4NO3 Homocyclo- NoVN CH2 N-Nor nite (D CHr-N-CH (3) DPT-l-I-INOs-i-NI-IiNOs IIomocyclonite (I) DPT plus Cyclonite (II) (4) DPT-i-I-INOs-l-AczOAcAn (VIII) iii (5) DPT-|-106%IINO3- 106 (VII) (6) 1o6+RoH 1o6E (IX) VEZ@ (7) AcAn-l-HNO3 106 (VII) (8) 106+HOAc AcAn (VIII) 35 2NH3+ 50H20 2NH1N02 (vi) PLATE ii Reactions of DP T $02 N O z-N--CHz-N-N O 2 (IJHz-N- C H2 Noz-N NNo,

CH9N-CH5 CHa-Il'- Hz NO2 NO2 II (Cyclonite) 1 (Homocyclonlte) Examp les 11 and 12 III (DPT) Example 15 NO2 NO2 NO2 Example 16 IX (106-E) PREPARATION oF DPT 1. BY NEUTRALIZATION oF MOTHER LIQUoRs FROM THE NrTRoLYsIs or HEXAMINE Example 1 Hexamine was treated with a large excess of absolute nitric acid (from to 25 moles of acid per mole of hexamine) according to the procedure described by Hale, Jour. Amer. Chem. Soc., 47, 2754 (1925). The hexamine (preferably admixed with Dry Ice) was added in small proportions to the concentrated nitric acid, the latter being stirred slowly but continuously and held below 25 C. by means of an acetone-Dry Ice bath. Each portion was allowed to dissolve before the introduction of the next. The time of addition may vary from about 75 to 140 minutes. during which the reaction mixture is held at C.

After all the hexamine was added, the reaction mixture was poured over twice its weight of crushed ice and the resulting precipitate of cyclonite was immediately filtered from the mixture. The cold ltrate, which smelled strongly of formaldehyde, was then promptly but cautiously neutralized with aqueous ammonia to a pH of about 5.6 (solution barely blue to bromocresol green). After about 15 minutes precipitation was complete and the solution became more acid. The mixture was then filtered and the crude product (melting at about 188 to 193 C., plus or minus 5 to 10 C.) was further purified by repeated recrystallization from nitromethane. The melting point of the puried product was thus raised to about 205 to 206 C.

The weight ratio of DPT to cyclonite produced by the foregoing process varied from about 1:5 to 1:6, although a 1:4 ratio was occasionally obtained. Generally speaking, it has been found that the optimum yields of DPT are obtained provided the reaction mixture resulting from the nitrolysis of hexamine is diluted with water as quickly as possible after the hexamine addition is complete. Furthermore it appears that the yield of DPT, in contrast to that of cyclonite, is inversely aiected by the quantity of nitric acid used, within certain limits.

The neutralization of the nitrolysis mother liquors may be effected with any suitable alkali other than the ammonia employed in Example 1. This is illustrated in Example 2.

Example 2 The reaction mixture from 40 g. (0.285 mole) of hexamine and 180 ec. (4.28 moles) of 99.6% nitric acid was diluted with ice and water immediately after the addition of the hexamine was complete, and the cyclonite wasv promptly filtered from the mixture: 46.2 g. of cyclonite, or 73.19% of the theoretical yield, was obtained. The cold filtrate after the separation of the cyclonite was then neutralized with saturated aquen ous sodium carbonate solution to a pI-I of 5.6. The yield was 6.43 g. of DPT, representing a 10.3% yield. A mixed melting point with a sarnple of DPT obtained as in Example 1 was not lowered.

The product obtained by the procedure described in Example 1 or 2 consists of 3,7-dinitropentamethylenetetramine (III) or DPT. This new compound melts with decomposition land sublimation at a somewhat indenite temperature, particularly in the crude state. However, after repeated recrystallizations, the melting point of DPT may be raised to approximately 204 to 205 C., using acetone, methyl ethyl ketone, nitromethane or any other suitable solvent for recrystallization. In this connection, it may be mentioned that DPT exists in two polymorphic modifications melting at 222 to 223 C. and 204 to 205 C., respectively.

DPT is decomposed rapidly by boiling water and slowly by boiling alcohol. It is decomposed easily by heat and darkens on melting; if heated at C. for 16 to 18 hours it gives a mixed sublimate which apparently consists of paraformaldehyde and hexamine. The chemical properties of DPT will be discussed more fully hereafter under the heading of Reactions of DPT.

AnaZysis.-Calcd C5Ii1oN6O4: C, 27.50; H, 4.58; N, 38.5. Found: C, 27.72; I-I, 4.48; N, 38.9.

'2. BY TREATMENT or HEXAMINE WITH NHiNOs-HNQs SOLUTION l-Iexarnine may be converted to DPT (III) without the production of cyclonite by treatment at moderate temperature with nitric acid containing dissolved ammonium nitrate. This method is described in Example 3.

Example 3 To a solution of 20 cc. (0.48 mole) of 95% nitric acid and 17.2 g. (1.21 mole) of ammonium nitrate at room temperature was added 14 g. (0.10 mole) of hexamine. After four hours the resulting slurry set to a solid (hexamine dinitrate). After the reaction mixture had stood at room temperature for approximately two weeks, the solid was dissolved in 200 cc. of water; no insoluble residue remained and therefore no cyclonite was present. The resulting aqueous solution was neutralized with 28% aqueous am-` monia to a pI-I of 5.6, producing 1.23 g. of DPT, corresponding to a yield of 5.6% of the theoretical. After recrystallizaticn from methyl ethyl ketone, a mixed melting point of the resulting product with a sample of DPT prepared as in Example 1 was not lowered.

3. BY TREATMENT or HEXAMINE DINITRATE WITH AcETrc ANHYDRIDE Considerably better yields of DPT may be obtained by rst converting hexamine (IV) to hexamine dinitrate (V) and then treating thev latter compound with a carboxylic acid anhydride at moderate temperatures for a considerable period of time. The procedure, starting with hexamine dinitrate, is described in Example 4.

Example 4 A mixture of 2220 cc. (20' moles) of acetic an? 4. BY TREATMENT or HEXAMINE DINITRATE WITH SULFURIC ACID Hexamine dinitrate may be converted to DPT by treatment with sulfuric acid in lieu of the acetic anhydride employed in Example 4. The sulfuric acid method is described in Examples and 6.

Erample 5 0.1 mole of hexamine dinitrate and 0.92 mole of 90% aqueous sulfuric acid were mixed together over a 30 minute period with proportionate addition of the reactants to the reaction vessel, and with eicient stirring. The reaction mixture was maintained at about 8 to 15 C. After the reactants had been added to the reaction vessel the mixture was stirred at about C. for 45 minutes and then poured into 400 ce. of ice and water. After filtration, the iltrate was neutralized to a pH of 5.6 to 6.5 using 28% aqueous ammonia, producing 0.31 mole of DPT, corresponding to 31% of the theoretical yield.

Example 6 A solution of 13.3 g. (0.05 mole) of hexamine dinitrate and 34 g. (0.31 mole) of 90% aqueous sulfuric acid, prepared by proportionate addition at 8-15" C. over a thirty minute period, was subsequently stirred at 15 C. for 45 minutes after the addition was complete. The resulting mixture, if neutralized with ammonia as in Example 5, supra, would have given a 31% yield of DPT. instead of following this procedure, however, the reaction mixture was poured into 55 cc. (1.24 mole) of well-stirred 99% nitric acid over an 8 minute period, the temperature of which was maintained at 10C' C. The resulting reaction mixture was then stirred at C. for a period of time indicated in Table I, infra, and then crowned in an ice-water mixture. The resulting cyclonite was filtered, dried, weighed in the crude state, fumed-off with 70% nitric, filtered, dried and again weighed. The filtrate from the initial separation of the cyclonite was cautiously neutralized with ammonia to a pH of 5.6, and the yield of DPT thus obtained was determined. The results are given in Table I.

Example 7 0.062 g. (0.001 mole) of nitramide (Organic Syntheses, vol. 1. 68 (1939)) was mixed with 0.48 cc. (0.006 mole) of formalin and the resulting solution was cooled to prevent gas evolution. After two minutes the solution was diluted with water and then cautiously neutralized to pH 5.6 with dilute ammonia. A precipitate slowly formed. The yield of DPT was 80 mg. corresponding to 73% of theoretical yield. The product was identified by mixed melting point with the DPT obtained in Example 1.

Example 8 DPT may also be prepared by reacting nitramide with formaldehyde and treating the resulting solution with methylenediamine sulfate (Knudsen, Ber. 47, 2700 (1914)). This reaction mixture on being neutralized to pH 7 with aqueous sodium carbonate yields DPT.

To a solution prepared by dissolving 0.10 g. (0.0016 mole) of nitramide in 0.12 cc. (0.0016 mole) of 40% formalin with cooling, was added 0.20 g. (0.0008 mole) of methylenediamine sulfate. The slurry was immediately diluted with 7.5 cc. of water and neutralized to pH 7 with aqueous sodium carbonate solution. The DPT which settled out slowly on keeping the reaction mixture at 0 C. for twenty minutes, weighed 78 mg. Yield of DPT calculated on the formaldehyde basis is 88%.

In view of the foregoing examples, it will be apparent that DPT may be formed by numerous alternative methods.

The chemical characteristics of DPT obtained by any of the foregoing procedures are of considerable interest and these will now be described.

B. REACTION OF DPT One of the most interesting and important properties of DPT resides in the fact that it may be converted in excellent yields to a new explosive compound, cyclotetramethylenetetranitramine or TABLE lr-CYCLONlTE-DPT YIELDS IN EXAMPLE 6 It will thus be apparent that under these reaction conditions the DPT yields vary approximately inversely with the cyclonite yields.

5. BY CoNDiNsATioN or FORMALDEHYDE, NITRAMIDE AND AMMONIA The foregoing methods of preparing DPT all start with hexamine or one of its salts. DPT may also be produced by condensing about 10 to 12 moles of formaldehyde with about 2 moles of nitramide (VI) at about 0 to about 30 C. and then treating the reaction product with ammonia according to the procedure outlined in Example 7.

homocyclonite, the probable structure of which is as follows:

C Hn-N- C H2 N O z-N N-N O a C Ha-N-(l) Hz (Homocyclonite) As previously indicated, homocyclonite is an explosive equal in ballistic strength and brisance to cyclonite, and has the same oxygen balance;

it is therefore an explosive of great power and brisance.

By still other reactions DPT may be converted to a substance (hereinafter identified by the trivial name AcAn) which consists of 1,9- diacetoxypentamethylene-2,4,6,8 tetranitramine (VIII), having the following structure:

NO2 IIOz I|\TO2 NO2 CHaC O O CHa-N-CHz-N-CHz-N-C Hz-N-CHrO-C O CH3 VIII (AeAn) Furthermore, if DPT is treated with nitric acid containing sufficient dissolved nitrogen pentoxide to titrate as apparently 106% HNOs, there is obtained still another explosive compound (hereinafter designated by the trivial name 106) which consists of 1,9-dinitroxypentamethylene-2, 4,6,8-tetranitramine (VII):

This latter compound is the nitroxy analog of the diacetoxy compound, AcAn, and these two compounds are in fact interconvertible. Moreover, the dinitroxy compound (VII) may be converted by treatment with alcohol to a new series of ethers, viz., 1,9-dialkoxypentamethylene- 2,4,6,8-tetranitramine (IX), these ethers (hereinafter designated as 106-E) having the probable formulae:

The reactions of DPT as diagrammatically indicated in Plate II are illustrated in the examples given below.

1. CONVERSION To HoMooYoLoNITE WITH CONCEN- TRATED Nrrxro ACID Homocyclonite may be obtained by treating DPT with concentrated nitric acid at about to 30 C. This procedure is illustrated in Example 9.

Example 9 DPT was treated with 99.6% nitric acid at about 20 C. using 30 parts by weight of acid to one part by weight of DPT. The crude material thus obtained melted at about 230262 C. The crude material was purified by digestion with aqueous ammonia which preferentially destroys any cyclonite contained in the crude product. Thereafter the material was digested with 70% nitric acid and nally recrystallized from nitromethane. The product melted at 279.5 to 280 C. corr. (with decomposition). It consists of cyclotetramethylenetetranitramine (I) having the probable structural formula:

N02 om-ilr-CHR Noi-N N-Noz (lJHz-N-Hz I (Homocyclouitc) Analysis- Calw for CiHsNsOa: C, 16.22; N, 37.84. Found: C, 16.4; N, 38.24. Molecular Weight: Calcd for CiHaOsNs, 296; Found, 296.

Homocyclonite is an explosive having properties similar to those of cyclonite (II). It has approximately the same power (i. e., about 150 compared to 100 to TNT) and brisance as oyclonite.

The solubility of homocyclonite, generally speaking, resembles but is somewhat lower than that of cyclonite. It is quite appreciably less soluble in many organic solvents, for example, acetic acid and dioxane. Homocyclonite may be conveniently recrystallized from any solvents ncluding acetone, methyl ethyl ketone, acetic acid, nitromethane, dilute nitric acid and the like.

In regard to its chemical properties, homocyclonite is also similar to cyclonite. Thus it is as stable toward 70% nitric acid as cyclonite. Likewise it is decomposed slowly by concentrated nitric acid. However, homocyclonite is' considerably more stable than cyclonite toward weak alkalis (e. g., aqueous ammonia or aqueous sodium bicarbonate), and this property provides a convenient method of preferentially destroying the cyclonite in cyclonite-homocyclonite mixtures in the preparation of pure homocyclonite.

It has been found that homocyclonite accompanies the cyclonite produced in the process described and claimed in the copending application ,of Scheissler and Ross (Serial No. 2,599, led

February 16, 1943), laccording to which a formaldehyde-producing substance (e. g., paraformaldehyde) is treated with ammonium nitrate in the presence of a carboxylic acid anhydride (e. g., acetic anhydride). Although the principal product of this reaction consists of cyclonite, a small proportion of homocyclonite usually accompanies the main product.

It has also been found that homocyclonite accompanies the cyclonite produced by the process described and claimed in the copending application of Bachmann (Serial No. I198,078, filed July 16, 1943). This latter process involves the treatment of hexamine or hexamine dinitrate with ammonium nitrate, also in the presence of a carboxylic acid anhydride, and as pointed out in said Bachmann application, the presence of homocyclonite in the product of the reaction is not objectionable from the viewpoint of explosive power and strength since the two components are substantially identical in their ballistic properties.

' melting point vs. composition, for cyclonitehomocyclonite mixtures Containing from 0 to 40% homocyclonite. This plot enables a rough estimation of the percent homocyclonite in mixtures of these two explosives where the cyclonite component predominates.

Eatwmple 10 Crude homocyclonite was reiiuxed with ammonia and then with 70% nitric acid, after which it was recrystallized from nitromethane; melting point 279.5-280" C. corr. Cyclonite was prepared by the Hale procedure and recrystallized from nitromethane, dioxane and glacial acetic acid; melting point, 203.3-205 C. corr. Synthetic mixtures of cyclonite and homocyclonite were then prepared from the purified components and the melting points of the various mixtures were determined. The results are given in Table II.

TABLE IL MELTING POINT OF CYCLONITE- HOMOCYCLONITE MIXTURES Percent Homocyclonito in Composition Melthslfomt In the case of the mixtures, the upper temperature indicated in the melting point spread (representing the temperature at which liquefaction was complete), was difficult to reproduce. Plate III represents a plot of percent composition against the lower temperature and the upper temperature of the melting point for mixtures containing from to 40% homocyclonite. The melting point of cyclonite-homocyclonite mixtures therefore provides a rough indication of the percent composition within Certain limits.

The crystallographic and impact sensitivity properties of homocyclonite are more particularly described in the copending application of Johnson, Blonquist, and McCrone, Serial No. 495,081, led July 16, 1943, wherein it is pointed out that the homocyclonite which accompanies the cyclonite produced by the Bachmann process may exist in any one of several polymorphic forms or modifications that are characterized by widely different impact sensitivities, approximately of the following order of magnitude:

Beta homocyclonite, ca. 33 cm. Alpha homocyclonite, ca. 12 cin. Gamma homocyclonite, ca. 7 cm. Delta homocyclonite, ca. cm.

These data were determined on a testing machine which gave a sensitivity reading of ca. 43 cm. for pure cyclonite. Because of the relatively high sensitivity of the alpha, gamma and delta polymorphic modification of hornocyclonite, in the manufacture of cyclonite by the Bachmann or by the Schiessler and Ross processes, provision is desirably made in order to ensure that the homocyclonite present in the final product exists in the least sensitive or beta polymorphic modification. The above indicated Johnson et ai. application describes and claims a method of purifying cyclonite compositions containing homocyclonite, in order to ensure that this condition is obtained. The same application also describes the technique of producing and isolating any desired polymorphic modifications of homocyclonite and its transformation into any other desired modification. Reference may be had to the Johnson et al. application for a more detailed description of homocyclonite polymorphism and the control thereof during manufacture of composition containing this interesting new explosive.

Because of its great explosive power and brisance, generally speaking, homocyclonite may be substituted for cyclonite as its substantial equivalent in the preparation or" various commercial or military explosives. Thus it may be mixed with molten TNT to form a castabie slurry suitable for shell loading. Likewise homocyclonitc may be phlegmatized (e. g., for press loading) by incorporating therewith a small proportion ,of beeswax or polymorphous hydrocarbon wax, as described in the copending application of Kistiakowskyet al., Serial No. 495,085, filed July 16, 1943. If so desired, homocyclonite may be substituted for cyclonite in the preparation of a plastic explosive such as that described and claimed in the copending application of Iistiakowsky et al., Serial No. l$5,086, filed July 16, 1943. It will thus be apparent that homocyclonite is a new explosive compound of wide utility for military and commercial purposes, and of equal power and brisance to the most powerful explosive heretofore known.

2. CONVERSION 'ro HoMocYcLoNrrE WITH Acmic ANHYDRIDE AND AN AMMONIUM NITRATE-NURIC Acro SOLUTION The yield of homocyclonite per mole of DPT may be increased by about by treating DPT at about 50 to 100 C. (preferably titl-75 C.) with a solution consisting of ammonium nitrate dissolved in nitric acid (in lieu of nitric acid alone), together with acetic anhydride. This process is illustrated by Example ll.

Eample 11 A mixture of l0 g. (0.046 mole) of DPI and 48.2 ce. (0.394 mole) of acetic anhydride was placed in a reaction vessel and stirred at 60 to C. While a solution of 11.1 g. (0.138 mole) of ammonium nitrate in 13.4 cc. (0.319 mole) of 99.6% nitric acid was added over a l5 minute period. During the addition the suspension (BIOT in anhydride) dissolved and a new precipitate appeared before the addition was complete. Thereafter the reaction mixture was stirred for 22 minutes at 52 C. and then for le minutes at 25 C. The reaction mixture was then pou-.red into 400 g. of ice-water mixture. The solid was ltered and washed with 200 to 380 cc. of water. The product was suspended in 200 cc. of 70% nitric acid and heated until strong evolution of brown fumes ceased (hereinafter referred to as the fume-GEW. VThe reaction mixture was then immediately cooled and 2000 cc. of water was added. The mixture was filtered and the precipitate dried at 70 C. The yield was 3.88 g. of homocyclonite, corresponding to 55.5% of the theoretical; melting point of the crude material, 267 to 288 C. A mixed melting point of the purified material with the homocyclonite obtained in Example 9 was not lowered.

A inodiiication of the procedure described in Example ll is given in Example l2. In this iodiiication the fume-oit" is avoided and the crude material is digested with water to destroy hydrolyzable impurities.

Eamplc 12 i solution of 44 g. of ammonium nitrate in 47 cc. or 98% nitric acid was prepared and allowed to stand until it became colorless and ceased gassing. In a two-liter, three-necked iiask equipped with a thermometer and a mechanical stirrer was placed 189 g. of DPT and 460 cc. of acetic anhydride. The slurry was heated to 53 C. by means of a water bath and the nitric acid-ammonium nitrate solution was then added over a period of l0 minutes, the temperature being held at 60 to 65 C. during the addition. During the first five minutes of the addition, the reaction was highly exothermic and it was necessary to keep the bath at about 20 to 30 C. However, during the last live minutes of addition a bath temperature of around 40L7 C.

13 afforded suiiicient cooling. When the addition was half complete it was observed that the reaction mixture had become a clear solution and no solid DPT remained. However as the addition continued the mixture became opaque.

After the addition the mixture was stirred at 60 to 65 C. for one hour. The rst crystals of homocyclonite were observed about three minutes after the completion of the addition. Heat was evolved for some five to ten minutes after the addition had ceased and care was therefore taken in raising the temperature of the water bath. At the end of the hour the bath was removed and the mixture allowed to cool. When the temperature of the reaction mixture reached 50 C., 450 cc. of cold water was rapidly added with stirring. As the water was added, the temperature fell to about 40 C. and then rose to about 90 C. The crude hornocyclonite was heated in the dilute mother liquor for l2 hours on a steam bath under a reflux condenser. During this period considerable gas wasevolved, much of it consisting of formaldehyde. The reaction mixture was then cooled and iiltered. Yield, 102 g.; melting point 272 to 276 C. (corr.). Recrystallization from acetone gave about 80 g. (rst and second crops); melting point (first crop) 279-280D C. and (second crop), 278-279" C. (corr.). If exceptionally pure homocyclonite is desired it may be further purified by recrystallization from nitromethane, acetone or other suitable solvents.

When DPT is treated in the presence of acetic anhydride with ammonium nitrate dissolved in nitric acid according to the procedure described in Examples 11 and 12, the product predominantly consists of homocyclonite although a small proportion of cyclonite is also usually produced. However, by varying the amount of acetic anhydride, and/or the amount of ammonium nitrate employed in the foregoing examples, the relative proportion of cyclonite to homocyclonite in the product may be considerably varied. Thus if the anhydride is greatly reduced or omitted entirely, the relative proportion of cyclonite in the product is increased over that given in the foregoing examples. Moreover, if the amount of ammonium nitrate employed per mole of DPT is decreased, the relative proportion of homocyclonite in the reaction product increases. The concentration effects are illustrated in Example 13.

Example 13 A mixture of 0.05 mole oi ammonium nitrate, 0.16 mole of acetic anhydride and 0.3 mole oi' acetic acid was stirred at 65 to 70 C., while 0.05 mole of DPT and 0.99 mole of 99% nitric acid were added alternately in 20 portions over a 20 minute period, the nitric acid addition being made in all cases about 15 seconds before the corresponding DPT addition. After the addition was complete, the reaction mixture was heated gradually to 90 C. over a 15 minute period. Thirty-five cc. of hot Water was then added and the resulting solution stirred at 90 C. for 3D minutes. Aiter cooling the reaction mixture to C. it was iiitered and the melting point and weight of the dried precipitate were determined.

A portion of the product was iumed cli with 70% nitric acid and the thus-purified material was then dissolved under reflux in 85 to 100% acetone. When all the material was in solution, water was added until crystallization just began (70 yto 75% acetone). Thereafter the resulting suspension was refluxed for' one hour and then further diluted by the addition of water to form a 50% acetone solution, the water being added slowly over a 30 minute period. Thereafter the acetone was distilled until only 10% of it remained in the residue, which was then reluxed one hour, after which the residual acetone was removed andthe solution cooled. This procedure of purication results in the conversion of the homocyclonite to a crystalline form most suitable for the mechanical separation described below.

The ltered, carefully puriiied precipitate was centrifuged in 15 g. of iodobenzene. The hornocyclonite-rich fraction settled to the bottom of the iodobenzene while the cyclonite-rich fraction accumulated on the surface. Based on this method of separation it was found that the product consisted of approximately 22% cyclonite and about 78% homocyclonite.

In a comparable run in which the amount of ammonium nitrate was doubled the product was found to consist of about 55% cyclonite and about 45% homocyclonite.

summarizing the results obtained in the experiments described in Example 13: if l mole of ammonium nitrate is employed per mole of DPT, the reaction mixture consists predominantly of homocyclonite (ca. 22% cyclonite, 78% homocyclonite) if, on the other hand, 2 moles of ammonium nitrate are employed per mole of DPT the product consists predominantly of cyclonite (ca. 55% cyclonite, 45% homocyclonite). Example 13 therefore illustrates the control over the composition of the product that may be e1"- fected by variations in the proportions of the reactants.

3. CONVERSION To CYcLoNrrE AND HoirccYoLoNrrE BY SULrURIo Aon) TREATMENT FoLLowEn Br Nirxor.- Ysis or THE REAcrIoN MIx'rURE Example 1 4 1.0 g. (0.0046 mole) of DPT was dissolved in 4.5 cc. (0.07 mole) of 86% sulfuric acid at 0 C. over a ten minute period. The solution was then added over a three minute period to 11.8 c. c. (0.28 mole) of 99% nitric acid at 0 C. The resulting clear solution was stirred 30 minutes at 25 C., then drowned in 120 cc. of ice and water. The crude cyclonite thus produced weighed 0.44 g. (43% of the theoretical yield, based on one mole cyclonite per mole of DPT) when fumed oi with 4 cc. of 70% nitric acid gave an 30% recovery of cyclonite-homocyclonite mixture, M. P. 194-198 C., softening at 193 C. Based on the melting diagram (Fig. 1) the product contains about 5% homocyclonite. When the filtrate remaining after the separation of the crude cyclonite was neutralized with ammonia, no DPT could be recovered.

4. CoNvERsIoN or DPT 'ro AoAN In Example 11 supra the conversion of DPT to a mixture of cyclonite and homocyclonite by means of acetic anhydride and a solution of ammonium nitrate in nitric acid is described. If this procedure is followed except that the ammonium nitrate is entirely omitted, homocyclonite is not produced. Instead a compound, 1,9- diacetoxypentamethylene 2,4,6,8tetranitramine (VIII) (herein designated by the trivial name fAcAnO is produced to the extent of about i ofl the theoretical yield. This compound has the probable structure.

The preparation of AcAn is described in Example 15.

Eample 0.2 g. (0.0009 mole) of DPT is suspended in 4.07 ce. (0.043 mole) of acetic anhydride maintained at 65 C. by means of a water bath, while 1.3 cc. (0.31 mole) of 99.6% nitric acid is added with stirring. Vigorous bubbling occurs with the evolution of brown fumes. Within three minutes a precipitate appears. After 16 minutes at 65 the reaction mixture was poured on ice; yield, 0.239 g. of a solid melting at 18.23 C., softening at 179.2n C. This compound gave a positive Franchimont nitrarnine test, was not very sensitive to shock, and was completely destroyed by heating with 70% nitric acid. After three recrystallizations from nitromethane and one from acetone the melting point was raised to 186.5 to

AnalysiS.-Calcd for CgHieNsOiz: C, 25.2; H, 3.76; N, 26.2; CI-I3C0, 19.8. Found. C, 25.3; H, 3.93; N, 26.2; CHsCO, 20.6, 20.3.

The compound was destroyed slowly by refluxing with 28% aqueous ammonia (82% in 68 minutes). It is stable to nitric acid at 25 C. for ve hours but is decomposed by 7 0% warm nitric acid. Absolute nitric acid at 0 C. converts it to 106, infra.

5. CONVERSION or DPT To 10(3" As above pointed out, when DPT is treated with absolute nitric acid as in Example 9, homocyclonite is produced. However', if DPT is treated at about 0-30" C. (preferably below 20 C.) with 106% nitric acid (i. e., absolute nitric acid containingr sufficient dissolved nitrogen pentoxide to titrate as apparently 106% acid), a '72% yield of a new linear compound melting at 204.5 to 205 C. is obtained, rather than homocyclonite. rThis product obtained with 106% nitric acid (for which reason it is herein designated by the trivial name l06) is the dinitroxy analogue of AcAn, and has the following probable structure (VII):

The preparation of 166 is described in Example 16.

Example 16 10 g. (0.046 mole) of DPT was added to 63 cc. (1.6 mole) of 106% nitric acid over a 35 minute period. The temperature of the reaction mixture was maintained below 20 C. and provision was made to ensure anhydrous conditions in the reaction mixture. A precipitate formed before the addition of the DPT was complete. Following the addition, the reaction mixture was stirred at room temperature for l5 minutes and then poured into ice-water mixture, filtered and the solid material washed with water and air-dried. The yield was 13.4 g. (72% of the theoretical) of a compound melting in the crude state at 191.5 to 193 C. (corn), softening at l89.5 C. This crude material was recrystallized from hot nitromethane, which raised its melting point to 204.5 to 205 C.

Found:

C, 13.7; H, 2.52; N, 31.7 14.0 2.40 31.7 13.5 2.42 33.0 13.8 2.40

The product (106) was destroyed rapidly when heated with 70% nitric acid or when boiled for 50 minutes with water. It was insoluble in cold butanol, not very soluble in acetone, ethyl acetate, ethanol or benzene but fairly soluble in pyridine and toluene.

It was detonated easily and violently and gave a positive Franchimont nitramine test. 1t is indeed an explosive of abnormal power and sensitivity. Its sensitivity is 12 times that of TNT and at a density of 0.69 it has a Trauzel block expansion of 588 cc. compared to 256 cc. for TNT.

AcAn (VIII) and 106 (VII) are interconvertible. Thus, if AcAn is treated with absolute nitric in the cold (e. g., at 0 C.), 106 is obtained. On the other hand, if 106 is treated with sodium acetate and acetic acid at an elevated temperature (e. g., at the boiling point) AcAn is obtained. The interconversion of these two compounds is illustrated in Examples 17 and 16, respectively.

Eample 17 30 g. of AcAn was added over a 30 minute period to 205 cc. of stirred 99.3% nitric acid maintained at 8 C. by means of an ice bath. After the addition was complete, the ice bath was removed and the reaction mixture was stirred for 20 minutes after which it was poured into 200 g. of ice-water mixture. The solid was filtered, washed with water and then washed with methanol. The yield of 106 was 30 g. or 98.8% of the theoretical. The melting point was 204.5 to 205 C. A mixed melting point with a sample of 106 prepared as in Example 16 was not lowered.

Example 18 To a solution of 0.23 g. of sodium acetate in 5 cc. of acetic acid was added 0.3 g. of 106. The mixture was heated to boiling for three minutes and then cooled and filtered. The solid material was washed with water, leaving 0.20 g. of material melting at 183 C. A mixed melting point with AcAn prepared as in Example l5 was not lowered. Analysis: Calcd for Cgi-116108012: N, 26.4. Found, N, 26.5.

The nitroxy groups in 106 may readily be replaced by alkoxy groups by treating 106 with an alcohol at the boiling point. Examples 19 and 20 illustrate the preparation of the new dimethoxyand the diethoxy-pentamethylene2,4,6,8tetra nitramines (IX), respectively, by this type of reaction. These compounds are of interest because of their relative stability compared to 106.

Example 19 0.2 g. (4.6)(10-1 mole) of compound 106 in 10 cc. of absolute methanol was refluxed for ten hours. After cooling, the crystalline deposit was filtered and washed with methanol. M. P. 18'2-3 C. (soft 177 C). Yield 0.16 g. After two recrystallizations from 1:1 dioxane-methanol, it melted at 182483 C. Analysis: Calcd for Cfzi-lisNsOio: C, 22.6; I-I, 4.32; N, 30.8. Found: C, 22.6; H, 4.27; N, 30.7.

Example 20 Diethoxypentamethylene 2,4,6,8 tetranitramine was prepared in a manner similar to that used in Example 19, except that 95% ethanol was used in place of methanol. A 43% yield of a product melting at 166-167 C. was obtained. Analysis: Calcd for CgHzoNaOio: C, 27.0; H, 5.04; N, 28.0. Found: C, 27.4; I-I, 4.94; N, 28.2.

It will be apparent to those skilled in the art that many variations may be made in the foregoing procedure without departing from the spirit and scope of the invention. We therefore intend to be limited only in accordance with the following patent claims.

Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, we declare that what We claim is:

1. A method of preparing 3,7-dinitropentamethylenetetramine which comprises treating hexamine with concentrated nitric acid, separating the cyclonite thus produced from the nitrolysis mother liquor, adjusting said mother liquor to a pH of about 5.6 to precipitate 3,7- dinitropentamethylene-tetramine and removing the precipitate from the liquor.

2. A method as dened in claim 1 wherein the precipitate is treated with nitromethane and recrystallized.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,147,226 Alquist Feb. 14, 1939 2,355,770 Wyier Aug. 15, 1944 2,395,773 Wyler Feb. 26, 1946 OTHER REFERENCES Hale, Journal American Chemical Soc., vol. 47, 1927, pp. 2754-2763.

Chemie and Industrie, v01. 28, 1932, pp. 1038- 1044.

Claims

1. A METHOD OF PREPARING 3,7-DINITROPENTAMETHYLENETETRAMINE WHICH COMPRISES TREATING HEXAMINE WITH CONCENTRATED NITRIC ACID, SEPARATING THE CYCLONITE THUS PRODUCED FROM THE NITROLYSIS MOTHER LIQUOR, ADJUSTING SAID MOTHER LIQUOR TO A PH OF ABOUT 5.6 TO PRECIPITATE 3,7DINITROPENTAMETHYLENE-TETRAMINE AND REMOVING THE PRECIPITATE FROM THE LIQUOR.