THE POLAR REACTION CONSTANT FOR ALKENE CHLORINATION.SIMILARITY AND DIFFERENCES IN THE CHLORONIUM AND BROMONIUM ION LIKE TRANSITION STATES.

Article abstract of DOI:10.1016/S0040-4039(00)87590-5

The polar reaction constant, p^*_Cl2, for the addition of free chlorine to alkenes, obtained in methanol at 25 deg C by direct kinetic methods, is -2.9 whereas p^*_Br2 is -3.1.The change form bromination to chlorination is associated with a large selectivity increase but a small drop in selectivity.This result is discussed in terms of the Hammond postulate and dependence of the charge distribution on the bridging atom in the halonium transition states.