Electronic factors in the elimination kinetics of 2‐halosubstituted methanesulphonates in the gas phase

The kinetics of the gas‐phase elimination of two 2‐haloethyl methanesulphonates were determined in a static system over the temperature range 310–380°C and pressure range 26–174 Torr. The reactions in seasoned vessels, with the free‐radical inhibitor propene and/or toluene always present, are homogeneous and unimolecular, and follow a first‐order rate law. The rate coefficients are given by the Arrhenius equations: for 2‐bromoethyl methanesulphonate log k 1 (s −1 ) = (11·70 ± 0·43)–(172·8 ± 4·8) kJ mol −1 (2·303 RT ) −1 and for 2‐chloroethyl methanesulphonate log k 1 (s −1 ) = (11·67 ± 0·50)–(173·9 ± 6·0) kJ mol −1 (2·303 RT ) −1 . The bromo compound was found to be more reactive than the chloro compound. At 340°C, for Br k 1 = 9·46 × 10 −4 s −1 and for Cl k 1 = 7·12 × 10 −4 s −1 . Apparently, electronic factors seem to be operating in these elimination reactions.