Neighboring Phenyl Participation in Gas-Phase Pyrolysis Kinetics of ω-Phenylalkyl Methanesulfonates

Article abstract of DOI:10.1021/j100371a027

The gas-phase pyrolysis or elimination of several phenylalkyl methanesulfonates were studied in a static system, seasoned with allyl bromide, and in the presence of the free-radical chain inhibitor propene and/or toluene.The working temperature and pressure ranges were 280-340 deg C and 22-155 Torr, respectively.The reactions obey first-order rate law, are homogeneous, and undergo a unimolecular elimination.The temperature dependence of the rate coefficients is given by the following Arrhenius equations: for 2-phenylethyl methanesulfonate, log k₁ (s^-1) = (12.19 +/- 0.31) - (167.2 +/- 3.4) kJ mol^-1(2.303RT)^-1; for 3-phenyl-1-propyl methanesulfonate, log k₁ (s^-1) = (11.54 +/- 0.65) - (163.2 +/- 7.3) kJ mol^-1(2.303RT)^-1; and for 4-phenyl-1-butyl methanesulfonate, log k₁ (s^-1) = (12.33 +/- 0.19) - (168.9 +/- 2.1 kJ mol^-1(2.303RT)^-1.The C6H5 substituent at the 2- and 4-position of the C-O bond of the methanesulfonate appears to participate in the rate of pyrolysis.The five-membered conformation which is a favorable structure for anchimeric assistance yields to some extent a cyclic product, tetralin.Participation of the phenyl group at the 3-position seems to be absent.