The factors affecting changes in the measured selectivity for the photochlorination of 2,3-dimethylbutane (DMB) in alkane solvents and in CCl 4 have been identified. At low chlorine concentrations in CCl 4 as solvent, the selectivities, S m = [2-ClDMB]/[1-ClDMB], are dramatically enhanced because of CCl 4 and Cl 3C • participation in the overall chain process. In the absence of CCl 4, the selectivities may also increase at very low chlorine concentrations because residual O 2 and peroxyl radicals participate in the overall chain process. In the absence of either of the above phenomena, S m was calculated to be 0.64, a value that compares well with a value of 0.62, which we have measured in the gas phase.
Journal of Organic Chemistry53, no. 22 (1988): 5220–5225.