Multiple-photon chemistry in the laser-jet: photochemistry of the 4-biphenylmethyl radical

Abstract

In laser-jet (LJ) photolysis (high intensity) of the ether 4-(4-benzoylphenoxymethyl)biphenyl 1 a two-photon process is observed in CCl₄ to yield 4-(chloromethyl)biphenyl 5 as product (3%), while the one-photon product is 4-biphenylaldehyde 7 (100% in conventional photolysis versus 97% in laser-jet photolysis). In ethanol, the results suggest a three-proton reaction in which 4-(ethoxymethyl)biphenyl 6 is produced in appreciable amounts (18%) in addition to the one-photon product 1,2-bis(4-biphenyl)ethane 4, the latter as the major product (82%). It is proposed that under high-intensity LJ photolysis conditions the electronically-excited 4-biphenylmethyl radical 2* is photoionized to the 4-biphenylmethyl cation 2⁺ and that the latter is trapped by ethanol to give the 4-biphenylmethyl ether 6.