Equilibria in the halogenation of some organic substances in aqueous solution

Measurements of redox potential have been used to obtain equilibrium constants for the reaction of iodine and bromine with aqueous solutions of ketones, esters and nitro-paraffins. Many of the iodination constants have an accuracy of a few per cent, but the bromination constants are not reliable to better than a power of ten. The iodination constants vary over 10 powers of ten, corresponding to considerable differences in the nature of the carbonhydrogen and carbon-iodine bonds involved. The data are used to derive the heat of the reaction RH + I-> RI + H in the gas phase, and the mean value obtained (46 kcal/mole) is consistent with earlier estimates. Approximate values are also derived for the equilibrium constants of the reaction RI->R- + I+ in solution. For variations in R these are roughly parallel with the acid dissociation constants of the reaction RH->R- + H+.