SOLVENT EFFECTS ON THE RATE OF REACTION OF CL2.- AND SO4.- RADICALS WITH UNSATURATED ALCOHOLS

Rate constants have been measured in several aqueous/organic solvent mixtures for the addition reaction of Cl2.- radicals with 2-propen-1-ol and 2-buten-1-ol as a function of temperature and with 2, 3-dimethyl-2-butene at room temperature. The rate constants were in the range of 10(6)-10(9) L mol-1 s-1, the activation energies were relatively low (1-10 kJ mol-1), and the pre-exponential factors varied over the range log A = 7.9 to 9.4. The rate constants (k) decreased (by up to a factor of 30) upon increasing the fraction of organic solvent and log k correlated linearly with the dielectric constant for a given water/organic solvent system, but the lines for the different solvent systems had different slopes. A better correlation of log k was found with a combination of the solvatochromic factor, E(T)(30), and the hydrogen-bond donor acidity factor, alpha. This suggests that the rate of reaction is influenced by the solvent polarity and also by specific solvation of the ionic reactant and product. Solvent effect on the reaction of SO4.- with 2-propen-1-ol was studied for comparison.