The addition of bromine to unsaturated aldehydes

Abstract

Earlier work on halogen addition, claimed to have established the bimolecular character of the reaction. As far as the effects of constitution were concerned, it was simply stated that negative groups reduced the rate of addition of halogen. In recent times, these approximate concepts have been considerably elaborated. Robertson and co-workers (9.) have shown that the addition of bromine to ethylene compounds is heterogeneous in solvents of low internal pressure. These reactions show the expected acceleration when the reaction vessel is filled with glasswool or glass beads; which thus increases the surface area and also decreases the average striking distance of the molecules from the surface. The reactions also exhibit negative temperature coefficients and an abnormal diminution in rate on decreasing the concentration of the reactants; thus showing that there is a limiting temperature, above which the adsorbed film becomes unstable, with a rapid diminution in reaction rate. Also, for a given solvent at each temperature, there is a limiting concentration below which the surface film becomes unstable.