Kinetics of neopentyl chloride pyrolysis. I. The molecular decomposition

Abstract

A detailed investigation of the thermal decon~position of neopentyl chloride over the temperature range of 410-496 "C established that the pyrolysis occurs via two concurrent processes: (i) a unimolecular decon~position accompanied by a Wagner-Meerwein rearrangement giving methylbutenes and hydrogen chloride and (ii) a radical-chain decomposition to methane, isobutene, methyl chloride, l-chloro-2-methylpropene, 3-chloro-2-methylpropene, 1,l-dimethylcyclopropane, and hydrogen chloride. The molecular reaction accounts for 30-40% of the overall decomposition. The Arrhenius equation for the molecular process is given by Icl(s-') = 1013.26*0.36e-60 000*16401Rr. The nature of the transition state for the decomposition is discussed in terms of the unique molecular structure of neopentyl chloride.

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

“…Thus, formation of 2‐methylbutenes from neopentyl chloroformate must take place via another mechanism. In association with the work reported in , a DFT study of the reaction mechanism of the gas‐phase thermal decomposition kinetics of neopentyl halides at 451ºC (721 K) was reported .…”

“…It is important to point out that the product neopentyl chloride from reaction (2) does not decompose to 2‐methylbutenes under the conditions of the present experiments. On our timescales, this compound requires higher temperatures of 410–496ºC (683–769 K), to yield 2‐methylbutenes through an intramolecular Wagner–Merwein rearrangement. As a check, experiments with of neopentyl chloride (1‐chloro‐2,2‐dimethylpropane; 99% pure; Aldrich) showed no decomposition in our apparatus at temperatures of 350–380 ºC (623–653 K).…”

Substituent effects in the gas‐phase eliminations of alpha;‐substituted alkyl chlorides the pyrolyses of 2‐chloro‐3‐methylbutane and pinacolyl chloride

“…CHaC-CHClCH, 4 CaHi, + HCI in vessels seasoned with the products of decomposition of allyl bromide, indicates that for long reaction times the final pressure Pf should be twice the initial pressure PO. Experimentally, the average results of P,/Po obtained out of five different temperatures were: 1.98 for 2-chloro-3-methylbutane [reaction (2)j and 1.96 for pinacolyl chloride (3-chloro-2,2-dimethylbutane) [reaction (3)].…”

Theoretical study of neighboring group participation of methyl ω‐chloroesters elimination kinetics in the gas phase

“…In 1967, Maccoll and Thomas [9] considered a very polar transition state in terms of an intimate ion-pair intermediate (4 Scheme 1) and presented several evidences in support of this idea: (a) the activation energies decreased while the rates increased by a-substitution with electron-releasing groups, (b) electron-releasing substituents at the b-position of the C-X bond gives small increase in rates, (c) as described above, [6] there is a strong correlation between energies of activation and the heterolytic bond dissociation energies, (d) a characteristic feature of positive carbon ion behavior in solution, such as the Wagner-Meerwein rearrangement, has been described in the gas-phase pyrolysis of neopentyl chloride [10,11] and isobornyl chlorides, [12,13] (e) a similarity charged transition state or intermediate appears to take place in the gas-phase pyrolysis and in nucleophilic substitution (S N 1) and elimination reactions (E1) in polar solvents.…”