1,4-addition reactions nitramines

The anions of primary nitramines, like other nucleophiles, can undergo Michael 1,4-addition reactions with a range of a,-unsaturated substrates to form secondary nitramines of varying molecular complexity (Equation 5.18). Kissinger and Schwartz prepared a number of secondary nitramines from the condensation of primary nitramines with a,/3-unsaturated ketones, esters, amides and cyanides. In a standard experiment a solution of the primary nitramine and... 

Michael addition reactions are particularly useful when linear aliphatic bis-nitramines are used because the products contain two terminal functional groups like in the diester (182). The terminal functionality of such products can be used, or modified by simple functional group conversion, to provide oligomers for the synthesis of energetic polymers such oligomers often use terminal alcohol, isocyanate or carboxy functionality for this purpose. 

In addition to the Ross-Schiessler process, utilising p-CH20 and AN, the synthesis of RDX/ HMX mixts has also been reported starting with other smail molecules (Ref 7), namely, methyl-amine nitrate methylene diamine dinitrate and nitramine (NH2N02) in combination with CH20. In these reactions, the intermediate formation of Hexamine or a cyclic analog, is not necessarily established... 

Irradiation of the UDMH + Oq Reaction Products. One experiment was conducted in which the UDMH + O3 reaction products (with UDMH in slight excess) were irradiated by sunlight. The results are shown in Table I and Figure 1. It can be seen that rapid consumption of UDMH, the nitrosamine, and HONO occurred, with N-nitrodimethylamine (also dimethyInitramine) and additional formaldehyde being formed. The formation of nitramine upon irradiation of the nitrosamine is consistent with results of previous studies in our laboratories (9,10), and probably occurs as shown ... 

Nitramines are known to photodissociate from their jt,jt state to give aminyl and nitric oxide radicals in the presence of an acid the aminyl radicals are protonated to give aminium radicals, which can initiate addition to olefins. As a synthetic reaction, photolysis of nitramines in the presence of acids can be conveniently run under oxygen to give oxidative addition similar to those shown in equation 145 indeed TV-nitrodimethylamine is photolysed with triene 299 under such conditions to give a mixture of 301 and 302, similar to results observed in the oxidative nitrosamine photoaddition169. To simplify the isolation, the crude products are reduced with LAH to form the open-chain amino alcohol 303. Some other oxidative photoadditions of N-nitro dimethylamine to other olefins are reported. As the photoreaction has to use a Corex filter and product yields are no better than those shown by nitrosamines, further investigations were scarcely carried out. 

The dehydration of the nitrate salts of some primary and secondary amines can yield the corresponding nitramine. Dimethylnitramine has been prepared in 65 % yield from the dehydration of dimethylamine nitrate in acetic anhydride to which 4 mole % of anhydrous zinc chloride has been added." The same reaction in the absence of chloride ion only generates a 5 % yield of dimethylnitramine." Some arylnitramines derived from weakly basic amines have been prepared via the addition of the amine nitrate salts to acetic anhydride. " ... 

Primary nitramines contain an acidic proton which enables them to behave as nucleophiles and undergo addition and condensation reactions. These reactions are extremely useful in two respects. Firstly, these reactions convert primary nitramino functionality into secondary nitramino functionality, which is no longer acidic and much more chemically stable. Secondly, these addition and condensation reactions can be used to prepare functionalized derivatives of polynitramines which can be used to synthesize energetic polymers and other explosive compounds. 

The order and timing of the addition of reagents in the KA-process is varied but in a typical procedure three reagents, namely, acetic anhydride, a solution of ammonium nitrate in nitric acid, and solid hexamine dinitrate, are added slowly, in small portions and in parallel, into the reaction vessel which is preheated to 60-80 °C. On completion the reaction mixture is often cooled to 50-60 °C and the RDX filtered and sometimes washed with acetic acid. This process produces a product which melts over a 2 °C range but the RDX still contains up to 10 % HMX as a by-product. Dilution of the reaction mixture with water before removing the RDX produces a very impure product containing numerous unstable linear nitramine-nitrates. Based on the assumption that one mole of hexamine dinitrate produces two mole of RDX the KA-process commonly yields 75-80 % of RDX. 

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 combustion performance of a rocket motor is dependent on various physicochemical processes that occur during propellant burning. Since the free volume of a rocket motor is limited for practical reasons, the residence time of the reactive materials that produce the high temperature and high pressure for propulsion is too short to allow completion of the reaction within the limited volume of the motor as a reactor. Though rocket motor performance is increased by the addition of energetic materials such as nitramine particles or azide polymers, sufficient reaction time for the main oxidizer and fuel components is required. 

CHAPTER 15 THE PREPARATION OF NITRATE ESTER NITRAMINES mixture. Then add 800 milliliters of methylene chloride to the reaction mixture, and then place 420 grams of diethanolamine into the second addition funnel. Now, remove the ice bath, and replace it with a cold-water bath. Then slowly add both the 70% nitric acid, and the diethanolamine to the reaction mixture, drop wise, and simultaneously while stirring the reaction mixture (drip the 70% nitric acid into the reaction mixture at a rate slightly faster then the diethanolamine. It should take 90 minutes for the drop wise addition of the diethanolamine, and about 70 minutes for the drop wise addition of the 70% nitric acid). Maintain the reaction mixture below 25 Celsius during the additions. After both additions are complete, gently heat the reaction mixture to 40 Celsius, and hold this temperature for ten minutes while stirring the reaction mixture. 

An important reaction is the addition of primary nitramines to an active double bond. This was reported by Kissinger and Schwartz [37) for example (18) ... 

The conclusion drawn that the first two steps in the decomposition of TNAZ involve NO2 loss agrees with the observation by Brill and coworkers [5] that gaseous NO2 was the most abundant species in the initial phases of the thermal decomposition of bulk TNAZ. That the NO2 concentration decreases from its initially observed level in the bulk study is evidence that this species is already undergoing significant secondary reactions at the time of its initial appearance yet the surmisal that the NO2 is a primary product is correct. Additionally, the observation that no methylene nitramine formation occurs agrees with the same conclusion drawn from the bulk study where the N2O/H2CO pair was not present. However, the absence of NO as an initial product in the molecular beam experiment, shows that the NO observed in the bulk decomposition study is not due to gas phase unimolecular nitro-nitrite isomerization followed by NO loss. 

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