The Thermal Decomposition of Methyl Azide. A Homogeneous Unimolecular Reaction

Leermakers, John A.

doi:10.1021/ja01335a007

Cited by 29 publications

(11 citation statements)

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“…Other studies reached similar conclusions, 14 although it was also noted that the relatively small difference in barrier heights was consistent with the observation of both singlet and triplet products. 15 Early experiments on the pyrolysis of methyl azide in the gas phase showed that it was a unimolecular reaction, 21,27 which produces nitrogen, hydrogen, and HCN, 27,28 as well as methyleneimine CH 2 NH. 29 The activation energy was reported in 1933 by Leemarkers as about 43.5 kcal/ mol.…”

Section: Introductionmentioning

confidence: 99%

Understanding the rate of spin-forbidden thermolysis of HN3 and CH3N3

Besora

Harvey

2008

The Journal of Chemical Physics

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The pyrolysis of the simplest azides HN(3) and CH(3)N(3) has been studied computationally. Nitrogen extrusion leads to the production of NH or CH(3)N. The azides have singlet ground states but the nitrenes CH(3)N and NH have triplet ground states. The competition between spin-allowed decomposition to the excited state singlet nitrenes and the spin-forbidden N(2) loss is explored using accurate electronic structure methods (CASSCF/cc-pVTZ and MR-AQCC/cc-pVTZ) as well as statistical rate theories. Nonadiabatic rate theories are used for the dissociation leading to the triplet nitrenes. For HN(3), (3)NH formation is predicted to dominate at low energy, and the calculated rate constant agrees very well with energy-resolved experimental measurements. Under thermal conditions, however, the singlet and triplet pathways are predicted to occur competitively, with the spin-allowed product increasingly favored at higher temperatures. For CH(3)N(3) thermolysis, spin-allowed dissociation to form (1)CH(3)N should largely dominate at all temperatures, with spin-forbidden formation of (3)CH(3)N almost negligible. Singlet methyl nitrene is very unstable and should rearrange to CH(2)NH immediately upon formation, and the latter species may lose H(2) competitively with vibrational cooling, depending on temperature and pressure.

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Section: Introductionmentioning

confidence: 99%

Understanding the rate of spin-forbidden thermolysis of HN3 and CH3N3

Besora

Harvey

2008

The Journal of Chemical Physics

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“…[OI The very small yields of CH4, C2H4, C2Hs, and HN3 suggest that neither of the processes (1) of the thermal decomposition of CH3N3, which reported that C2H4 and H S 3 were important products, suggested that reaction [0"] accounted for 25y0 of the initial step. However, the conversions in that work were extensive, and sometimes complete.…”

Section: Primary Actmentioning

confidence: 99%

“…The mechanism of the thermal decomposition of methyl azide, as proposed by Leermakers (1) and by Rice and Grelecki ( 2 ) , appears to be rather complex and to involve more than one initial step. However, those experiments were carried to such high conversions that the initial reaction was obscured.…”

Section: Introductionmentioning

confidence: 99%

The Photochemical Decomposition of Methyl Azide

Currie¹,

Darwent²

1963

Can. J. Chem.

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A B S T R A C T T h e photolysis of methyl azide has been investigated in the vapor phase at low conversions and over suitable ranges o f pressure, temperature, intensity, and wavelength. Under all conditions t h e principal gaseous product was I\'z with small amounts o f H z (5-11%), and traces of C H 4 , C2H4, and C 2 H s . A condensate identified as ( C H B N ) , was also found.T h e quantum yield for t h e production o f K z is approximately 2, independent o f intensity (over a 45-fold range), temperature (17-100' C ) , and pressure (14- I . I N T R O D U C T I O NThe mechanism of the thermal decomposition of methyl azide, as proposed by Leermakers (1) and by Rice and Grelecki ( 2 ) , appears to be rather complex and to involve more than one initial step. However, those experiments were carried to such high conversions that the initial reaction was obscured.The photolysis of methyl azide has recently been investigated (3) in an inert matrix a t low temperatures. Milligan (3) found bands in the infrared corresponding to methylenimine but not t o the methylimino radical. He suggested that the methylimino radical isomerizes rapidly because of the excess energy from the photolysis:The photolysis has now been investigated, in the gas phase, a t small conversions, as functions of intensity, wavelength, pressure, and temperature. The effects of free radical scavengers and an inert gas have also been investigated. E X P E R I M E N T A L-- Materials ( a ) hfethyl azide.-Prepared b y the methylation o f sodium azide with methyl sulphate (4). T h e gaseous azide was dried with calcium chloride and condensed at -80' C . T h e condensate was distilled through a Vigreaux column and the fraction boiling at 20-21° C collected. T h a t fraction was purified further b y trapto-trap distillation i n vacuo at -80' C and the middle fraction retained. (b) Azonzethane.-Prepared b y the oxidation o f synlllletrical dimethylhydra~ine with cuprous chloride (5). T h e product was distilled and the middle fraction retained.(c) Ethylene, carbon dioxide, Apparatus T h e apparatus was a rather conventional all-glass high-vacuum system o f the t y p e used in gas kinetic studies. Mercury was rigorously excluded t o avoid dangers o f an explosion ( 7 ) . A circulating pump, o f the t y p e designed b y \Vatson ( 8 ) , was included in the reaction system t o ensure the proper mixing o f t h e gases.

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“…Among these rearrangements, the most investigated and documented are the keto enol equilibria [7±12]; however, fewer studies have been done on the imine enamine equilibria. Methanimine (CH 2 @NH), the simplest imine, was ®rst predicted by Leermaker [13] in 1933. It was proposed as an intermediate in the pyrolysis of methyl azide by Rice and Grelecki [14].…”

Section: Introductionmentioning

confidence: 99%

Theoretical analysis of some substituted imine-enamine tautomerism

Pérez

Toro–Labbé

2001

Theoretical Chemistry Accounts: Theory, Computation, and Modeli

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We present a theoretical study of the CH 3 CX NH CH 2 CX NH 2 tautomerism. The analysis is performed in terms of global descriptors of reactivity, such as electronic chemical potential, chemical hardness and chemical softness. Chemical hardness is used to study the relative stability in the frame of the maximum hardness principle. Chemical softness appears to be related to the molecular polarizability, and it is used to discuss relative stability in the context of the minimum polarizability principle. Both empirical rules are simultaneously satis®ed for this equilibrium. Transition states, in which the transferred proton is found about midway between the donor and acceptor atoms, are rationalized in terms of the BroÈ nsted coecient for the relative position along the reaction coordinate and the Marcus equation for the energy barriers. Substituent eects on the activation properties are analyzed in a partitioned form that probes the eect of the substituent group on the molecular properties at the ground-state and transition-state structures.

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The Thermal Decomposition of Methyl Azide. A Homogeneous Unimolecular Reaction

Cited by 29 publications

References 0 publications

Understanding the rate of spin-forbidden thermolysis of HN3 and CH3N3

Understanding the rate of spin-forbidden thermolysis of HN3 and CH3N3

The Photochemical Decomposition of Methyl Azide

Theoretical analysis of some substituted imine-enamine tautomerism

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