Theoretical calculations on the mechanisms of the gas-phase elimination kinetics of 2-chloro-1-phenylethane, 3-chloro-1-phenylpropane, 4-chloro-1-phenylbutane, 5-chloro-1-phenylpentane, and their corresponding chloroalkanes: The effect of the phenyl ring

The kinetics and mechanisms of the dehydrochlorination of 2-chloro-1- phenylethane, 3-chloro-1-phenylpropane, 4-chloro-1-phenylbutane, 5-chloro-1-phenylpentane, and their corresponding chloroalkanes were examined by means of electronic structure calculation using density functional theory methods B3LYP/6–31G(d,p), B3LYP/6–31++G(d,p), MPW1PW91/6–31G(d,p), MPW1PW91/6–31++G(d,p), PBEPBE/6–31G(d,p), and PBEPBE/6–31++G(d,p). The potential energy surface was investigated for the minimum energy path. Calculated enthalpies and energies of activation are in good agreement with experimental values using the MPW1PW91 and B3LYP methods. The transition state of these reactions is a four-centered cyclic structure. The reported experimental results proposing neighboring group participation by the phenyl group was not supported by theoretical calculations. The rate-determining process in these reactions is the breaking of ClC bond. The reactions are described as concerted moderately polar and nonsynchronous. © 2011 Wiley Peiodicals, Inc. Int J Chem Kinet 43: 292–302, 2011