Strahlungschemie von Kohlenwasserstoffen. 15. Mitteilung. Energieübertragung im System Benzol–3-Phenylcyclohexadien-(1,4)

3-Phenylcyclohexa-1,4-diene, which is a reaction product in the benzene radiolysis, is decomposed when its solutions in benzene are irradiated by γ-rays. The main products are biphenyl (20%) and dihydrobenzene (10%). They show that hydrogen from phenylcyclohexadiene is transferred to benzene. The high G-value for the disappearance is explained by energy-transfer from a high-lying state of benzene, formed with g(B*) ≥ 2, to the diene. From the concentration dependence in the range 0.015–0.25 Mol/1 can be concluded that τ · k_tA is 21 1/Mole for phenylcyclohexadiene and 4 1/mole for cyclohexene, where τ is the lifetime of the excited state of benzene involved in the reaction and k_tA is the rate constant for energy-transfer from this excited state to the acceptor. This rate constant is in the same order of magnitude for biphenyl, naphthalene and cyclohexa-1,4-diene as accepted for phenylcyclohexadiene. The nature of the energy transfer from benzene to phenylcyclohexadiene is discussed. The possibilities of charge transfer or the lowest singlet- or tripletstate as excited states are ruled out.