Kinetic Studies on Bromine-Exchange Reactions of Antimony Tribromide with ￥á-Phenyl-n-butyl and ￥á-Phenyl-i-butyl Bromides in Nitrobenzene

摘要

The rate of bromine-exchange reaction between antimony tribromide and α-phenyl-n-butyl bromide in nitrobenzene has been determined, using antimony tribromide labelled with Br-82. The results indicate that the exchange reaction follows the first-order kinetics with respect to the organic bromide, and either the second- or first-order kinetics with respect to antimony tribromide depending on its concentration. The third-order rate constant obtained was 7.50 × 10-2 l2mol-2s-1 at 28℃. Similar study on the bromine-exchange reaction between antimony tribromide and α-phenyl-i-butyl bromide has also been carried out. The results of the study show the same kinetic orders as the ones observed with α-phenyl-n-butyl bromide. The third-order rate constant observed was 2.40 × 10-2 l2mol-2s-1 at 28℃. The activation energy, the enthalpy of activation and the entropy of activation for the two exchange reactions mentioned above have been determined. The reaction mechanisms for the exchange reactions are discussed.