A kinetic equation has been derived for a homogeneous catalysed reaction in which both the reactants of a bimolecular reaction are activated by the catalyst and the equation applied to the reaction between crotonic acid and bromine catalysed by hydrogen bromide. The variation of rate with change of catalyst is also indicated.

A study of the reaction between bromine and fumaric acid and bromine and stilbene brought out clearly the validity of the rate equation derived in the previous part. The uncatalysed addition reaction of fumaric acid exhibits the characteristics of a degenerate branching chain.

An analysis of the Arrhenius parameters for the addition reaction indicates that the reaction is a composite one and of the “slow” type. The influence of substituents on the energy of activation and on the frequency factor is discussed and the abnormal values of the latter are accounted for. A close correlation is also noticed between the two.