I n " seasoned ' ' reaction vessels gaseous cyclopentyl chloride decomposes in the range 309-376" by a nearly homogeneous first-order reaction to give cyclopentene and hydrogen chloride. The presence of cyclohexene does not affect the rate, and bromine causes only a slight acceleration. The rate is expressible as K, = exp (-48,30O/RT) (sec.7) and there is no variation in rate coefficient over the initial pressure range 40-400 mm. The results are consistent with a unimolecular elimination of hydrogen chloride. The faster rate compared with those of cyclohexyl chloride and s-butyl chloride is attributed t o steric acceleration.

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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.

Maccoll and Swinbourne. 149 23. Gas Phase Eliminations. Part V.* The Kinetics of the Pyrolysis of Neopentyl Chloride.

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