Methyl azide, decomposition

Thermal decompositions of alkyl azides are advantageously studied in millimole quantities using a PE spectroscopically controlled flow system under low pressure ( ), thereby reducing the hazards involved in handling these explosive compounds in bulk. Our investigations started with methyl azide, which splits off nitrogen unexpectedly only at temperatures above 500° C (37) ... 

These conclusions were anticipated by product studies. Alkyl azides are readily available and their thermal and photochemical decomposition reactions have been studied. In general, light and heat induced decomposition of methyl azide does not produce a MeN species that can be intercepted in respectable yields with a bimolecular trap. For example, attempts to trap MeN with cyclohexane as solvent produced only a 0.4% yield of adduct. Photolysis of CH3N3 or CD3N3 at cryogenic temperatures fails to produce an IR spectrum attributable to triplet methylnitrene. The IR spectrum of CH2=NH (or CD2=ND) is observed instead. " ... 

Quantum-chemical calculation of the decomposition of methylpentazole has shown that methylpentazole is as stable as aromatic pentazole derivatives <2003CEJ5511>. In the reaction of 1SN-Iabeled diazomethane with hydrazoic acid at — 80 °C, which leads to methyl azide, no methylpentazole intermediate has been detected <1932G716, 1958HCA1823>. Therefore, methylpentazole can only be synthesized by using a different route. Other substituents like CN, F, or NH2 lead to pentazoles with lower activation barriers (Table 5) than the known arylpentazoles. 

The consensus of the experimental work is that the initial decomposition step is cleavage of the RN-N2 bond, releasing N2, with an activation energy of about 40 kcal/mole [23,25]. For completeness, however, we began our investigation by computing the R-N3 dissociation energies for both 3 and 4, as well as for two model systems, methyl azide, 5, and n-propyl azide, 6. 

SAFETY PROFILE A corrosive and irritating material. It hydrolyzes into methanol and sodium hydroxide. May ignite spontaneously in moist air. Flammable when exposed to heat or flame. Ignites on contact with water. Violent reaction with (CHCI3 + CH3OH), (methyl azide + dimethylmalonate), FCIO3. When heated to decomposition it emits toxic fumes of Na20. 

This method has been exploited for the functionalization of [60]fullerene by using several aroyl azides166 and [2.4,6-tri-(tm-butyl)phenyl]oxycarbonyl azide16, which afforded the corresponding A -acylaziridines and subsequently the dihydrooxazoles, whereas azafulleroids were produced with [2-(trimethylsilyl)ethoxy]methyl azide and several benzylic azides presumably through the thermal decomposition of the intermediate dihydrotriazoles77. 

Methyl azide in the gas phase undergoes a homogeneous unimolecular decomposition in which the rate determining step is the characteristic nitrogen elimina-... 

Photolysis in the vacuum ultraviolet (1800-2400 A) resulted in the formation of nitrogen, ammonia and hexamethylenetetramine, in yields similar to the thermal decomposition. Hexamethyenetetramine was also a major product in photol-yses above 2400 A and it seems probable that both the thermal and photochemical decompositions proceed by the same mechanism. The solution photolysis of methyl azide has recently been examined and the general kinetic features are similar to the vapor-phase photolysis and thermolysis. Thus increases with CH3N3 concentration to a maximum of 2, and hexamethylenetetramine and N2 were the major products. It is believed that in solution CH3N does not isomerize but condenses with CH3N3 in several steps to produce hexamethylenetetramine. 

The thermal decomposition of triaryl methyl azides is first order, and the major products are mixtures of benzophenone anils . For the reaction... 

The latter compound gives a red solution izi liquid ammonia, azid with methyl iodide decomposition occurs in the following manner —... 

The decomposition of methyl azide in the presence of di-iron nona-carbonyl has been described briefly . The principal product of this decomposition was the complex (385), in addition to a 20% yield of... 

In analogy with HN3 the decomposition of the alkyl azides is believed to go through a singlet state. In the gas phase photolysis of methyl azide the primary step is the formation of methyl nitrene ... 

In practice, the azide decompositions are usually carried out in boiling toluene or xylene and give good yields of 3-alkyl-170,184,187 and 3-aryl-anthranils.185,188 Yields of 3-unsubstituted anthranils from o-azidoben-zaldehydes are generally much lower.170 The method has also been used to prepare 3-(j3-styryl)anthranils (106) from o-azidochalcones,189 3-methyl-naphtho[2,3-c]isoxazoles from 3-acetyl-2-azidonaphthalene,190 and 3-(2-pyridyl)anthranils from o-azidophenyl pyridyl ketones.191 This last reaction is of interest in that 2-(2-azido-3,5-dibromobenzoyl)pyridine in boiling toluene yields almost equal amounts of 5,7-dibromo-3-(2-pyridyl)anthranil (43%) and the zwitterionic pyrido[l,2-f>] cinnolin-6-ium 139 (41%). 

AZIDA SODICA (Spanish) (26628-22-8) Reacts with hot water. Explosive decomposition in elevated temperatures above 525°F/274°C. Forms ultra-sensitive explosive compounds with heavy metals copper, copper alloys, lead, silver, mercury, carbon disulfide, trifluoroacryloyl fluoride. Violent reaction with acids, forming explosive hydrogen azide. Violent reaction with bromine, barium carbonate, chromyl chloride, dimethyl sulfate, dibromomalononitrile. Incompatible with caustics, cyanuric chloride, metal oxides, metal sulfides, methyl azide, phosgene. 

If a free singlet nitrene is an intermediate, produced upon decomposition of a vinylazide, then the activation energy of vinyl nitrene rearrangement to azirine must be very small. The situation is similar to the case of methylnitrene, produced upon photolysis of methyl azide (see Section 5.3). 

EXPLOSION and FIRE CONCERNS noncombustible slightly volatile at ordinary temperatures NFPA rating (not rated) may explode on contact with 3-bromopropyne, ethylene oxide, lithium, peroxyfonnic acid, and chlorine dioxide vapor ignites on contact with boron diiodophosphide reacts violently with acetylenic compounds, metals, chlorine, chlorine dioxide, methyl azide, and nitromethane incompatible with acetylene, ammonia, chlorine dioxide, azides, calcium, sodium carbide, lithium, rubidium, and copper heating to decomposition emits toxic fumes of Hg use water spray, fog, or foam for firefighting purposes. 

Important synthetic paths to azirines and aziridines involve bond reorganization, or internal addition, of vinylnitrenes. Indeed, the vinylnitrene-azirine equilibrium has been demonstrated in the case of trans-2-methyl-3-phenyl-l-azirine, which at 110 °C racemizes 2000 times faster than it rearranges to 2-methylindole (80CC1252). Created in the Neber rearrangement or by decomposition of vinyl azides, the nitrene can cyclize to the p -carbon to give azirines (Scheme 4 Section 5.04.4.1). 

Copper catalyzes the decomposition of sulphonyl azides in benzene very slowly. When methanesulphonyl azide was boiled under reflux in benzene solution in the presence of an excess of freshly reduced copper powder, some decomposition occurred to give methanesulphonamide and azide was recovered 78>. Transition metal complexes have been found to exert a marked effect upon the yields of products and isomer ratios formed in the thermal decomposition of methanesulphonyl azide in methyl benzoate and in benzotrifluoride 36>. These results will be discussed in detail in the section on the properties of sulphonyl nitrenes and singlet and triplet behaviour. A sulphonyl nitrene-iron complex has recently been isolated 37> and more on this species will be reported soon. 

For the practical design of hypersurfaces, i.e. cuts through the (3n-6)dimensional hyperspace, some hints are outlined. The main purpose, however, is to illustrate the usefulness of hypersurface calculations especially for the detection, identification and characterization of unstable molecules. Examples chosen comprise the structure of RS-C=C-SR, the relative stability of thioacroleine isomers C,H S, the structural changes accompanying the oxidation of hydrazine and some of its derivatives, the isomerization of tetrahedrane to cyclobutadiene both thermally as well as on oxidation, the predicted existence of F SS and nonexistence of CI2SS or H2SS, and, finally, some aspects of the thermal decomposition of methyl and vinyl azides. 

Example VI Some aspects of the thermal decomposition of methyl and vinyl azides, H3C-N3 and H2C=CH-N3. 

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