Seven products (table 1) were isolated from the reaction at 313 nm of which only four have been reported previously. The quantum yields of formation were measured and the variation of yield with concentration and temperature studied. Addition of samarium chloride and piperylene quenched the formation of some products. From their behaviour the products fall into three groups : (a) the addition compounds, (b) dicyclohexene and (c) isopropanol.

Isopropanol and part of the dicyclohexene are formed as a result of hydrogen abstraction by triplet acetone from cyclohexene. The addition products are formed by rearrangement of an intermediate complex of triplet acetone and cyclohexene rather than by free radical reactions as suggested previously. The results are partly confirmed by some qualitative studies of the interaction of thermally produced radicals. The quantum efficiency for the formation of triplet acetone is approximately one. Ratios of the rate constants for reaction to deactivation of the triplet state have been determined.