Nitroalkanes, decomposition

It was demonstrated that free radicals formed in the decomposition initiate nitroalkane decomposition at temperatures some 200 °C lower than are normally necessary. For nitroethane m the temperature range 240-800° C the reaction follows first order kinetics with log (sec" ) = 11 and = 39 kcal.mole . For 1-nitropropane the values obtained were log (/f(sec ) = 13.3 and E = 48.5 kcal.mole". An initial reaction of type (a) was favoured for nitroalkanes. Mueller presents a somewhat different interpretation in that the initial decomposition of nitromethane occurs m two ways... 

Table 3.5 gives the most typical examples of acyclic nitronic esters, which have unusually high thermal stability. These data contradict the known data on fast thermal decomposition of alkyl nitronates derived from the simplest nitroalkanes (237) and relatively low thermal stability of nitronate (73a). On the basis of the available data, the following empirical mle can be derived an extension of the conjugation chain of the nitronate fragment increases stability of nitronates. 

In general, C-nitro compounds are more stable than /V-nitro compounds because of the higher bonding energies in the former type. Evidence is offered [1] that decomposition and explosion of many nitro-derivatives proceeds through the aci-form, and that sensitivity corresponds to the proportion of that present. In terms of this work, sensitisation by very small proportions of soluble organic bases is most important this is not limited to nitroalkanes. TNT can apparently be brought to the sensitivity of lead azide by this means. For a physicist s view of this sensitisation,... 

Some 1,3-dinitroalkanes (145) have been synthesized from the reaction of nitroalkanes with a-nitroalkenes (144) generated in situ from the decomposition of Mannich bases (143) derived from primary nitroalkanes. Reported yields for these reactions are low and the formation of by-products limits the feasibility of the method. 

Caution Distillation of nitroalkanes in general should be conducted behind a safety shield. To avoid decomposition of distillation residues the distillation apparatus should be cooled to 0°C prior to ventilating with inert gas. 

Few nitroalkanes have found use as explosives. Nitromethane (CH3NO2) is a notable exception, and there have been numerous studies of its decomposition pathway [42,43,44]. It has been reported that nitromethane is sensitized to detonation by acidic and basic media. This sensitizing effect is approximately linear with the pKa [45], The best explanation of the effect is that nitromethane undergoes autocatalytic decomposition by an ionic mechanism under acidic or basic conditions [46,47], Among other mononitroalkanes, nitroethane, the nitropropanes, and chloropicrin C13C(N02), have been the most extensively studied. The decomposition... 

Metal oxides increase the explosive sensitivity of nitroalkanes (e.g., nitromethane, nitroethane). Can react vigorously with reducing materials. When heated to decomposition it emits toxic fumes of Pb. See also LEAD COMPOUNDS and PEROXIDES. 

SAFETY PROFILE Poison by ingestion and intraperitoneal routes. Mildly toxic by inhalation. A human eye irritant. Human systemic effects by inhalation conjunctiva irritation. Mutation data reported. Very dangerous fire hazard when exposed to heat, open flame, or oxidizers. Reacts violendy with Ca(OH)2, hydrocarbons, hydroxides, inorganic bases. May explode on heating. Metal oxides increase its sensitivity to thermal ignition. To fight fire, use alcohol foam, CO2, dry chemical, water spray. When heated to decomposition it emits toxic fumes of NOx. See also 2-NITROPROPANE, NITROALKANES, and NITRO COMPOUNDS. 

The reaction has little value ft>r the preparation of nttroalkanes, but is of theoretical importance as it indicates the reactivity of nitrate esters It should be added that J. B. 1 e y [59) has found that thermal decomposition of nitrate esters resulted in the formation of small amounts of nitroalkancs. Thus the formation of nitroalkanes from nitrate esters seems to merit a more detailed examination of the mechanism of the conversion and decomposition. 

E. Other Electrophiles - Amino acids can be prepared either by direct introduction ot the amino function,85 or by elaborating hippuric acid by alkylation.66 A nitro group can be introduced directly, and, after decarboxylation, nitroalkanes are obtained.49 In addition to decomposition... 

DPE). C- and 0-phenylation reactions were not affected by its addition to the reaction medium. This stoichiometric chemical trapping method was also used in the study of other related reactions such as the C-phenylation of nitroalkanes and indoles, and in the thermal decomposition of (4-nitrophenoxy) tetraphenylbismuth derivatives. No free radicals were involved although, again, qualitative ESR studies had revealed their presence.28 (Scheme 6.19)... 

N,N DIPROP YL-4-TRIFLUORO-METHYL-2,6-DINITROANILINE (1582-09-8) Ci3HjsF3N304 Combustible solid (flash point >185 F/>85°C oc Fire rating 1). May react violently with barium, potassium, sodium. Incompatible with organic anhydrides, acrylates, alcohols, aldehydes, alkylene oxides, substituted allyls, cellulose nitrate, cresols, caprolactam solution, epichlorohydrin, ethylene dichloride, isocyanates, ketones, glycols, nitrates, phenols, vinyl acetate. Exothermic decomposition with maleic anhydride. May increase the explosive sensitivity of nitromethane. Reacts with nitroalkanes, forming explosive products. As a dinitroaniline derivative, the extremes of heat (do not store above 90°F/32°C), mechanical shock, and fnction might be... 

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