PHOTOLYSIS OF CHLOROBENZENE. PHENYLATION OF CHLOROBENZENE WITH ANOMALOUS ORIENTATION
Photolysis of chlorobenzene as neat and in concentrated solutions gives a mixture of o-, m-, and p-chlorobiphenyls in an anomalous ratio, with the highest ratio of the p-isomer. However, on dilution with solvent, the isomer ratio tends to approach the normal ratio as obtained from the usual phenylation of chlorobenzene with the highest ratio of the o-isomer. A mechanism is proposed in which a triplet excimer of chlorobenzene arising in concentrated solutions favours the production of the p-isomer.