Spectra nitramines

The Na salt of MEDINA was fluorinated in w, the sain extd with methylene chloride, and the solv evapd to give a yellow oil whose IR spectrum showed absence of NH and the presence of NF absorption, and analysis indicated was a mixt (Ref 22). Nitramines in the presence of sulfuric acid are capable of nitrating reactive aromatic compds, but when acetanilide was treated with MEDINA in the presence of this acid, no nitroacetanilide was isolated. Instead compds indicating that the MEDINA had been fragmented and the fragments reacted with the acetanilide were isolated (Ref 12)... 

Dark Decay of UDMH in the Presence of NO, When 1.3 ppm of UDMH in air was reacted in the dark with an approximately equal amount of NO, 0.25 ppm of UDMH was consumed and formation of -0.16 ppm HONO and -0.07 ppm N2O was observed after -3 hours. Throughout the reaction, a broad infrared absorption at -988 cm" corresponding to an unidentified product(s), progressively grew in intensity. The residual infrared spectrum of the unknown product(s) is shown in Figure 2a. It is possible that a very small amount (50.03 ppm) of N-nitrosodimethylamine could also have been formed but the interference by the absorptions of the unknown product(s) made nitrosamine (as well as nitramine) detection difficult. No significant increase in NH3 levels was observed, in contrast to the UDMH dark decay in the absence of NO. Approximately 70% of the UDMH remained at the end of the 3-hour reaction period this corresponds to a half-life of -9 hours which is essentially the same decay rate as that observed in the absence of NO. 

Several additives were tested with a series of explosives in order to enhance ESI intensities [15—17]. Nitramine and nitrate ester explosives showed enhanced response for ammonium nitrate additive, by forming [M + NOs] adduct ions in the negative-ion mode. Nitrate adduct ions were more intense than trifluoroacetate (TFA) or chloride adduct ions by a factor of 6-40. The base peak in the negative-ion mass spectrum of TNT, with 1 mM ammonium nitrate in the mobile phase was at m/z 226 due to the [M-H] ion. 

Fig. 3. Spectrum of typical secondary nitramine (2,5-dinitro-2,5-diazahexane), according to R. N. Jones and Thom [3].

A 500 ml round bottom flask equipped with thermometer and overhead stirrer containing 150 ml of nitric acid (98 %) was cooled to 10 °C to which propane diurea 10 g (0.064 mol) was added slowly in small portions under constant stirring and cooling below 18 °C. The reaction mixtiue was stirred at this temperature for 5 min and then 75 ml of acetic anhydride (97 %) was added dropwise at 21 °C to 23 °C. Under this condition the stirring was continued for 8—9 h and finally filtered to yield a white compound which was washed thoroughly and dried. The reaction was monitored by IR spectrum in KBr matrix till the disappearance of the NH peak at 3258 cm. The yield of the fully converted nitramine product was 17.6g (82%). Recrystallization from nitro-methane gave a compound of m.p. > 220 °C (deflagration). With this optimized conditions the batch size was enhanced to 10—15g. The compound was fully characterized by IR, H-NMR and elemental analysis. DTA results showed the decomposition peak temperature at 235 °C. 

Studies of the formation of HONO from secondary nitramines, R2N(N02) (R = -CH2-), illustrate an advance made possible by Fast Thermolysis/FTTR methods [I8]. HONO has been considered to be an important intermediate in the thermal decomposition of nitramines [19], but, because of its reactivity, was proposed based on indirect evidence [20,21] until this Fast Thermolysis/FTIR technique was applied. Cis- and trans-HONO are both present in the IR spectrum of the gas from RDX (see the PQR pair at 700-900 cm in Figure 2), but as shown in Figure 3, HONO is transient under the conditions of the experiment. The initial concentration most closely reflects its relationship to the composition of the parent molecule. Figure 4 shows the quantity of HONO as a percentage of the initial gas products for various nitramines [18] versus the H/NO2 ratio in the parent molecule. The general trend suggests that HONO arises from adventitious bimolecular encounters of H and N02 radicals in the condensed phase [18], rather than concerted decomposition of the 4- and 5-center unimolecular intermediates shown below that may contribute in the gas phase [22]. 

Tetiyl, a nitramine with a trinitroaromatic nucleus, gives a discrete chromatographic peak when analyzed by GG-MS so it was only natural to assume that the mass spectrum of this peak represented the mass spectrum of tetryl [22,23]. ffowever, it was found [24,25] that the mass spectrum was not that of tetryl but of 7V-methylpicramide. The latter is the hydrolysis product of tetryl, as shown in Figure 2. This hydrolysis, which takes place in the gas chromatrograph, most probably in the injector, is an example of an artifact which, if overlooked, may lead to an erroneous attribution of the mass spectrum of one compound N-methylpicramide) to another compound (tetryl). It demonstrates the caution that should be exercised in interpreting GG-MS results, especially of thermally labile compounds. 

While the decomposition of tetiyl under GG conditions is well established, it is still uncertain whether the highly nonvolatile heterocyclic nitramine HMX elutes intact from the GC column. While in some studies [12,22] decomposition was noticed, which led to difficulties in its GC (or GG-MS) analysis, it was claimed by others [23,26-29] that by carefully controlling the GC conditions, HMX may elute through the GC column without decomposition. However, a convincing mass spectrum proving the identity of the eluted compound was either absent [26,29] or it contained ions that could not identify HMX unequivocally [23,27,28]. 

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