Kinetie Studies of Photochemical Addition of Iodine to Cyclohexene

Several mechanisms have been proposed for the addition of iodine to double bond. We have studied kinetics of the addition of iodine to cyclohexene under the irradiation of the sample solution at the iodine absorption band in visible region and at the charge transfer band in ultraviolet region of the electron donor acceptor complex between iodine and cyc1ohexene. The apparent order of the reaction was 3/2 and 0.64 with respect to iodine and cyc1ohexene, respectively, when the sample solution was illuminated with visible light. We observed an evidence to suggest that the complex participates in the reaction from the study of temperature effect on the kinetics. However, kinetic data could not be fully explained by the complex participation mechanism alone. The experimental results seem to be explained by co-occurance of radical chain mechanism and complex participation mechanism in parallel. In case of the illumination of the solution with 315 nm light, the apparent order of the reaction was 2 and 0.64 with respect to iodine and cyclohexene, respectively. The electron donor acceptor complex may produce radicals upon the charge transfer absorption, and the subsequent eaction seems to proceed in the same way as illuminated with visible light because the apparent reaction order with respect to cyclohexene is same