Hexamine with nitric acid

It appears however that the reaction proceeds according to both equations simultaneously since ammonium nitrate and formaldehyde are formed according to equation (37) and C02, N2 and water according to equation (38). Some of the methylene groups and nitrogen atoms of hexamine are therefore not utilized for the production of cyclonite. The nitration of hexamine with nitric acid requires from four to eight times the theoretical amount of nitric acid. 

This may be explained by considering the nitration of hexamine with nitric acid as a stepwise degradation by nitrolysis, i.e. the nitration of amine involving the stepwise cleavage of the bond between the nitrogen and carbon atoms. According to Lamberton [39] this idea was first advanced by Linstead. The main work on this subject has been done by British [39] and Canadian [40] authors. 

Fig. 17. Temperature changes during the nitration of hexamine with nitric acid, according to Dunning, Millard and Nutt [50], 7—Anhydrous acid, nitration temperature 20°C 2—anhydrous acid, nitration temperature —35.5°C 3—96% acid, nitration temperature 20°C 4—96% acid, nitration temperature —35.5°C 5—90% acid, nitration temperature 20°C 6—90% acid, nitration temperature —35.5°C 7—85% acid, nitration temperature 20°C —85% acid, nitration temperature —35.5°C.

On the other hand, Wright et al. [47] found that the nitrolysis of hexamine with nitric acid in the presence of acetic anhydride but in the absence of ammonium nitrate involves a decrease of the yield of cyclic products. The amount of the chain compound (XXIII) formed is then increased. 

The transient formation of hexamine in method 4 was confirmed by Winkler, Gillies and Williams [60] (see equation (45)) who examined the reaction mechanism of cyclonite preparation by method 4. They found that hexamine dinitrate is formed at 35°C as an intermediate product. At the same time nitric acid is evolved hence nitrolysis of hexamine dinitrate may occur, in other words the mechanism of cyclo-nite formation would be similar to that of direct nitration of hexamine with nitric acid. 

Historical RDX was first synthesized by Henning (GerP 104280 of 1899) for medical use. He failed to nitrate hex amine directly with strong HNOa but first prepd hexamine dinitrate, CgH y 2N4-2HN03, by treating an aq soln of hexamine with nitric acid. The resulting wh crysts were collected, dried and added in small portions to HN03 (d 1.52)... 

With regard to the nitration of hexamine with nitric acid Singh [121] brouglu a small change to the charge distribution in compound (VIb - Vol. Ill, p. 89). and Lamberton et at. [122] added some more information on compound XIX (the same as la. Vol, III, p. 91). 

Tiiis process consists of continuous nitration of hexamine with nitric acid (98.5%), conliruious decoinpositiorr of the secondary products formed during nitration and continuous nitration of KUX from its spent acid. 

Chapman studied the nitrolysis of symmetrical methylenediamines. The nitrolysis of N, N, N, M-tetramethylmethylenediamine with nitric acid-acetic anhydride-ammonium nitrate mixtures gives both dimethylnitramine and RDX the latter probably arises from the nitroT ysis of hexamine formed from the reaction of ammonium nitrate and formaldehyde released from the hydrolysis of the methylenediamine. The same reaction with some morpholine-based methylenediamines (105) allows the synthesis of l,3,5-trinitro-l,3,5-triazacycloalkanes (106). 

Nitrolysis of hexamine dinitrate with nitric acid - ammonium nitrate - acetic anhydride... 

The presence of HMX as an impurity in RDX is not a problem when the product is used as an explosive. However, the need for an analytical sample of RDX makes other more indirect methods feasible. One such method involves the oxidation of 1,3,5-trinitroso-1,3,5-triazacyclohexane (109) ( R-salt ) with a mixture of hydrogen peroxide in nitric acid at subambient temperature and yields analytical pure RDX (74%) free from HMX." The same conversion has been reported in 32 % yield with three equivalents of a 25 % solution of dinitrogen pentoxide in absolute nitric acid. l,3,5-Trinitroso-l,3,5-triazacyclohexane (109) is conveniently prepared from the reaction of hexamine with nitrous acid at high acidity. ... 

The reaction of hexamine dinitrate (241) with 98% nitric acid at —30°C, followed by quenching with aqueous sodium nitrate, yields the nitrosamine (244). When the same reaction is cautiously quenched with ethanol the ethoxyether (245) is obtained. Treatment of the ethoxyether (245) with cold absolute nitric acid yields the bicyclic ether (246). ° Treatment of any of the cyclic nitramines (242)-(246) with nitric acid and ammonium nitrate in acetic anhydride yields RDX. ° Hexamine dinitrate is often used in low temperature nitrolysis experiments in order to avoid the initial exotherm observed on addition of hexamine to nitric acid. 

The above observations allow the selective formation of RDX, HMX or the two linear nitramines (247) and (248) by choosing the right reaction conditions. For the synthesis of the linear nitramine (247), with its three amino nitrogens, we would need high reaction acidity, but in the absence of ammonium nitrate. These conditions are achieved by adding a solution of hexamine in acetic acid to a solution of nitric acid in acetic anhydride and this leads to the isolation of (247) in 51 % yield. Bachmann and co-workers also noted that (247) was formed if the hexamine nitrolysis reaction was conducted at 0 °C even in the presence of ammonium nitrate. This result is because ammonium nitrate is essentially insoluble in the nitrolysis mixture at this temperature and, hence, the reaction is essentially between the hexamine and nitric acid-acetic anhydride. If we desire to form linear nitramine (248) the absence of ammonium nitrate should be coupled with low acidity. These conditions are satisfied by the simultaneous addition of a solution of hexamine in acetic acid and a solution of nitric acid in acetic anhydride, into a reactor vessel containing acetic acid. 

The final product of the action of nitric acid on hexamine or hexamine dinitrate is RDX see Vol 3, p C614. At low temps, however a number of other compounds are produced (Ref 2). Dilution of the hexamine dinitrate-nitric acid reaction mixture at low temperatures with ethyl ether and subsequent treatment of the gum so obtained with methyl and ethyl alcohols and water severally leads to l-alkoxy-3 5-dinitro-l 3 5-triazacyclohexane (IV), l 3-di-nitro-l 3 5-triaza-n-pentane 5-nitrate (V), and methylenedi-1 -(3 5-dinitro-1 3 5-triaza-cyclo-hexane) (VI). Dilution of the reaction mixture with methyl and ethyl alcohol produces mainly 3 5-dinitro-1 3 5-triazacyclohexane nitrate (II). 

Hexamethylenetetramine Explosive. A powerful solid explosive was claimed to have been prepd by oxidizing hexamine with a solution of hydrogen peroxide, treating the resulting product with nitric acid and then, reoxidizing with H202 (Ref 1). After drying, this was mixed with AN, castor oil and turpentine (Ref 2)... 

If hexamine is treated with nitric acid, or Cyclonite Dinitrate with Ac20 in sulfuric acid,... 

Another peroxide compound was prepd by Leulier (Ref 4) and repeated by v. Girsewald (Ref 5) on treating hexamine first with hydrogen peroxide and then with nitric acid. The resulting white crystals were presumed to be, HN (CH2CH2-OOH)2 mw 137.14,N 10.21%. 

The nitrolysis of hexamine can be controlled by changes in conditions to follow either of two paths. Strongly acidic conditions lead to triazine and linear triamine products. With nitric acid and acetic anhydride the dinitrotetraazabicyclo[3.3.1]nonane (328) is produced, and opening of the methylene bridge then gives the tetrazocane (329) and finally, in the presence of ammonium nitrate, HMX or the tetramine (330) (51JA2773). 

Reaction (39) is a hydrolysis of hexamine resulting in the formation of formaldehyde and ammonia, and reaction (40) consists of the oxidation of formaldehyde with nitric acid. 

The formation of hexamine dinitrate from hexamine and nitric acid proceeds with a heat effect of —AH=33.5 kcal/mole hexamine nitrate is also converted into dinitrate with a heat evolution of —4/7=15.7 kcal/mole. 

Nitration. In the production method employed in a factory at Bridgwater [55], the nitrator is fed continuously with nitric acid and hexamine and the product of nitration together with the acid flows off, also continuously. 

There is an alternative view(e.g. expressed by Wright et al. [59]) that hexamethylenetetramine is first formed and then nitrolysed. This assumption is said to be supported by the separation from the reaction products of both methods 4 and 5 of the cyclic products (XXIX) l-aceto-3,5-dinitro-l,3,5-triazacyclohexane and (XXX) 1-aceto-3,5,7-trinitro-l,3,5,7-tetrazacyclo-octane which may also be obtained from hexamine by treating it with nitric acid and acetic anhydride ... 

Bachmann et al. [64] also described the conditions under which the substance (XII) (DPT) can be prepared in a yield of about 20% from hexamine and nitric acid, in the presence of acetic anhydride and acetic acid, at temperatures between 15 and 30°C. On nitrolysis with nitric acid in the presence of ammonium nitrate and acetic anhydride at 60-65°C, this substance gives octogen in 80% yield. 

Hexamine undergoes degradative nitrosation to form either 1,3,5-trinitrosohexahydro-1,3,5-triazine or l,5-dinitrosooctahydro-l,3,5,7-tetrazocine, depending on the reaction conditions. At pH 1, (72) is formed exclusively, but between pH 3 and 6 only (73) is formed. It reacts with nitric acid and acetic anhydride in a similar way. 

N02. NH.CH2. N(N02).CH2. nh2. HN03, C2H8N607 mw 228.16 N 36.84% OB to C02 —7.01% cryst mp 129°, Sol in acet neutralized by aq Na hydroxide. Prepn is by diln of a hexamine dinitrate-nitric acid reaction mixt with eth at 0°, resulting in a gum. Evapn of the eth from the reaction mixt by addn of methanol with rapid stirring at RT, is then followed by recrystn of the resulting residue formed, after filtrn, with 80% nitric acid. The yield is 22%. Calcd power of the expl is 154% TNT (Ref 3) Refs 1) Beil, not found 2) K.W. Dunning ... 

The chemistry of the prepn of RDX is highly complex and remains not fully understood. What follows is a synthesis of the views of British and Canadian investigators (Refs 37a 41a) as summarized by Urbahski (Ref 82, pp88— 89). The following reactions presumably occur when hexamine is treated with nitric acid to produce RDX ... 

---