The thermal decomposition of methyl chloroformate

Johnson, R.L.; Stimson, VR

doi:10.1071/ch9771917

Cited by 6 publications

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“…The only two compounds lacking a C β –H bond on the alkyl side of the chloroesters for which the decomposition kinetics has been reported in the literature are methyl chloroformate and neopentyl chloroformate . In spite of this limited information, the rates obtained in the present work may be compared with the compound of reference methyl chloroformate, R = H [reaction (5)].…”

Section: Resultsmentioning

confidence: 99%

“…The Arrhenius equation was reported as log k 1 = (12.64 ± 0.20) – (183.6 ± 2.0) kJ mol −1 (2.303 RT ) −1 . The kinetic study of methyl chloroformate , under conditions of a deactivated reaction vessel and in the presence of an inhibitor, decomposed at very high temperatures of 425–480ºC (698–753 K) to give CH 3 Cl and CO 2 as final products, with parameters of (log k 1 = (14.26 ± 0.20) – (251.0 ± 2.0) kJ mol −1 (2.303 RT ) −1 . The rate of decomposition was found to be 4000 times slower than ethyl chloroformate.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics of the Gas-Phase Elimination Reaction of Benzyl Chloroformate and Neopentyl Chloroformate

Lezama

Domínguez

Chuchani

2014

Int. J. Chem. Kinet.

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The gas‐phase eliminations of benzyl chloroformate (475–523 K, 31–103 Torr) and neopentyl chloroformate (563–622 K, 37–70 Torr), in a deactivated static reaction vessel, and in the presence of a free radical suppressor, are homogeneous, unimolecular, and follow a first‐order rate law. The rate coefficients are expressed by the following Arrhenius equations: Benzyl chloroformate Neopentyl chloroformate Formation of neopentyl chloride: Formation of 2‐methylbutenes: The derived kinetic and thermodynamic parameters for benzyl chloroformate decomposition indicate the reaction proceeds through a concerted four‐membered cyclic transition state to give benzyl chloride and CO2 gas. Neopentyl chloroformate undergoes a parallel reaction, where neopentyl chloride formation may arise from a polar‐concerted four‐membered cyclic transition state, whereas the mixture of olefins, 2‐methyl‐2‐butene, and 2‐methyl‐1‐butene appears to be produced from a carbene intermediate. This intermediate seems to be originated from a concerted five‐membered cyclic transition state of the neopentyl substrate.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Kinetics of the Gas-Phase Elimination Reaction of Benzyl Chloroformate and Neopentyl Chloroformate

Lezama

Domínguez

Chuchani

2014

Int. J. Chem. Kinet.

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“…The rate constant found for the reaction ClC(O)OCCl 3 -2CCl 2 O follows the expression k ClC(O)OCCl 3 = 1.4 Â 10 13 exp[À(60.7 kJ mol À1 /RT)] (in units of s À1 ). Johnson et al 16 studied the pyrolysis of ClC(O)OCH 3 in the presence of inhibitors between 698 and 753 K and found methyl chloride and carbon dioxide as products according to the following homogeneous molecular reaction ClC(O)OCH 3 -CH 3 Cl + CO 2 (7) The rate constant is given by k 7 = 1.4 Â 10 (14.3AE0.2) exp[À251 AE 2 kJ mol À1 /RT] s À1 and the reaction proceeds by a four-center transition state. They also found that at temperatures above 700 K the reaction produces byproducts assigned to heterogeneous processes.…”

Section: Introductionmentioning

confidence: 99%

Thermal decomposition of FC(O)OCH₃ and FC(O)OCH₂CH₃

Berasategui

Argüello

Paci

2018

Phys. Chem. Chem. Phys.

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The thermal decomposition of methyl and ethyl formates has been extensively studied due to their importance in the oxidation of several fuels, pesticidal properties and their presence in interstellar space. We hitherto present the study of the thermal decomposition of methyl and ethyl fluoroformates, which could help in the elucidation of the reaction mechanisms. The reaction mechanisms were studied using FTIR spectroscopy in the temperature range of 453-733 K in the presence of different pressures of N2 as bath gas. For FC(O)OCH3 two different channels were observed; the unimolecular decomposition which is favored at higher temperatures and has a rate constant kFC(O)OCH3 = (5.3 ± 0.5) × 1015 exp[-(246 ± 10 kJ mol-1/RT)] (in units of s-1) and a bimolecular channel with a rate constant kFC(O)OCH3 = (1.6 ± 0.5) × 1011 exp[-(148 ± 10 kJ mol-1/RT)] (in units of s-1 (mol L)-1). However for ethyl formate, only direct elimination of CO2, HF and ethylene operates. The rate constants of the homogeneous first-order process fit the Arrhenius equation kFC(O)OCH2CH3 = (2.06 ± 0.09) × 1013 exp[-(169 ± 6 kJ mol-1/RT)] (in units of s-1). The difference between the mechanisms of the two fluoroformates relies on the stabilization of a six-centered transition state that only exists for ethyl formate. First principles calculations for the different channels were carried out to understand the dynamics of the decomposition.

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“…The kinetics of the gas‐phase elimination of alkyl chloroformates has been for years the subject of different mechanistic interpretations according to experimental conditions, structure of the substrates, and products formation . In this sense, it is noteworthy to classify the several types of esters of chloroformic acid studied at high temperatures and at subatmospheric pressures according to structures: (a) presence of the C β –H bond at the alkyl side of the chloroester; (b) absence of the C β –H bond but the presence of a C α –H bond at the alkyl side of the chloroester; (c) absence of both active C β –H bond and C α –H bond at the alkyl side of the chloroester.…”

Section: Introductionmentioning

confidence: 99%

“…The elimination kinetics of methyl chloroformate , lacking a C β –H bond, under homogeneous and molecular conditions (425–480ºC) yielded CH 3 Cl and CO 2 gas (log k 1 = (14.26 ± 0.20) – (251.0 ± 2.0) kJ mol −1 (2.303 RT ) −1 . The result of log A = 14.26 suggested the reaction to proceed through a four‐membered cyclic transition state type of mechanism.…”

Section: Introductionmentioning

confidence: 99%

Kinetic and Mechanisms of the Homogeneous, Unimolecular Elimination of Phenyl Chloroformate andp‐Tolyl Chloroformate in the Gas Phase

Lezama

Chuchani

2015

Int J of Chemical Kinetics

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The gas‐phase elimination of phenyl chloroformate gives chlorobenzene, 2‐chlorophenol, CO2, and CO, whereasp‐tolyl chloroformate produces p‐chlorotoluene and 2‐chloro‐4‐methylphenol CO2 and CO. The kinetic determination of phenyl chloroformate (440–480oC, 60–110 Torr) and p‐tolyl chloroformate (430–480°C, 60–137 Torr) carried out in a deactivated static vessel, with the free radical inhibitor toluene always present, is homogeneous, unimolecular and follows a first‐order rate law. The rate coefficient is expressed by the following Arrhenius equations: Phenyl chloroformate: Formation of chlorobenzene, log kI = (14.85 ± 0.38) – (260.4 ± 5.4) kJ mol−1 (2.303RT)−1; r = 0.9993 Formation of 2‐chlorophenol, log kII = (12.76 ± 0.40) – (237.4 ± 5.6) kJ mol−1(2.303RT)−1; r = 0.9993 p‐Tolyl chloroformate: Formation of p‐chlorotoluene: log kI = (14.35 ± 0.28) – (252.0 ± 1.5) kJ mol–1 (2.303RT)−1; r = 0.9993 Formation of 2‐chloro‐4‐methylphenol, log kII = (12.81 ± 0.16) – (222.2 ± 0.9) kJ mol−1(2.303RT)–1; r = 0.9995 The estimation of the kI values, which is the decarboxylation process in both substrates, suggests a mechanism involving an intramolecular nucleophilic displacement of the chlorine atom through a semipolar, concerted four‐membered cyclic transition state structure; whereas the kII values, the decarbonylation in both substrates, imply an unusual migration of the chlorine atom to the aromatic ring through a semipolar, concerted five‐membered cyclic transition state type of mechanism. The bond polarization of the C–Cl, in the sense Cδ+…Clδ−, appears to be the rate‐determining step of these elimination reactions.

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The thermal decomposition of methyl chloroformate

Abstract: In the presence of inhibitors, methyl chloroformate decomposes at 425- 480� to methyl chloride and carbon dioxide in a homogeneous molecular reaction. The rate constant is given by k1 = 10(14.26�0.20)exp[(-251000�2000)/8.314T] s-1

Cited by 6 publications

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Kinetics of the Gas-Phase Elimination Reaction of Benzyl Chloroformate and Neopentyl Chloroformate

Kinetics of the Gas-Phase Elimination Reaction of Benzyl Chloroformate and Neopentyl Chloroformate

Thermal decomposition of FC(O)OCH₃ and FC(O)OCH₂CH₃

Kinetic and Mechanisms of the Homogeneous, Unimolecular Elimination of Phenyl Chloroformate andp‐Tolyl Chloroformate in the Gas Phase

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The thermal decomposition of methyl chloroformate

Abstract: In the presence of inhibitors, methyl chloroformate decomposes at 425- 480� to methyl chloride and carbon dioxide in a homogeneous molecular reaction. The rate constant is given by k1 = 10(14.26�0.20)exp[(-251000�2000)/8.314T] s-1

Cited by 6 publications

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Kinetics of the Gas-Phase Elimination Reaction of Benzyl Chloroformate and Neopentyl Chloroformate

Kinetics of the Gas-Phase Elimination Reaction of Benzyl Chloroformate and Neopentyl Chloroformate

Thermal decomposition of FC(O)OCH3 and FC(O)OCH2CH3

Kinetic and Mechanisms of the Homogeneous, Unimolecular Elimination of Phenyl Chloroformate andp‐Tolyl Chloroformate in the Gas Phase

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Thermal decomposition of FC(O)OCH₃ and FC(O)OCH₂CH₃