Gas-Phase Elimination Kinetics of ω-Phenylalkyl Chlorides. Participation of the Phenyl Ring

Article abstract of DOI:10.1021/j100249a037

The kinetics of the gas-phase dehydrochlorination of several phenylalkyl chlorides were determined in a static system, seasoned with allyl bromide, and in the presence of the free radical inhibitor propene.The working temperature and pressure ranges were 398.8-480.6 deg C and 66-202 torr, respectively.The reactions are homogeneous, unimolecular, and follow a first-order rate law.The temperature dependence of the rate coefficients is given by the following Arrhenius equations: for 3-chloro-1-phenylpropane, log k₁ (s^-1) = (13.99 +/- 0.26) - (238.4 +/- 3.5) kJ*mol^-1; for 4-chloro-1-phenylbutane, log k₁ (s^-1) = (13.07 +/- 0.43) - (220.5 +/- 5.8) kJ*mol^-1 (2.303RT)^-1; and for 5-chloro-1-phenylpentane, log k₁ (s^-1) = (13.75 +/- 0.36) - (231.2 +/- 4.9) kJ*mol^-1 (2.303RT)^-1.When the rates of HCl elimination among each of the phenylalkyl chlorides are compared with those for the coresponding unsubstituted alkyl chloride, participation of the C6H5 group at the 3 position is more favored, while that at the 5 and 6 positions is rather weak.Participation of C6H5 group at the 4 position is apparently absent.