The factor which determines whether excitation of charge-transfer complexes leads to final net products in comparison with the reactivity on excitation of one of the components.

Selective excitation of charge-transfer complexes of indene or acenaphthylene with various electron acceptors does or does not afford final net reaction products, depending on the free energy of the resulting radical ion pairs over the ground state, -deltaGBET, with threshold values. A similar factor governs the efficiency of the reaction on direct excitation of either the donor or the acceptor of their components, except that it does not fall to nil below the threshold and the reaction affords higher quantum yields than the selective excitation of the charge-transfer complex.

Mechanisms of the Photochemical Rearrangement of Diphenyl Ethers.

The mechanism of the photochemical rearrangement of diphenyl ether (1a) was studied. Irradiation of 1a in ethanol gave 2-phenylphenol (2, 42%) and 4-phenylphenol (3, 11%) as rearrangement products, in addition to phenol (4, 30%) and benzene (5, 25%) as diffusion products. Cross-coupling experiments employing [(2)H(10)]1a demonstrated that the formation of 2- and 4-phenylphenol was an intramolecular process.