Kinetic analysis of aromatic photocyanation: naphthalene, biphenyl, and phenanthrene

Abstract

Nucleophilic photocyanation of the unsubstituted aromatic hydrocarbons, naphthalene, biphenyl, and phenanthrene, in both dry and aqueous acetonitrile can be described by a mechanism involving two photoinduced transients. The primary step of the mechanism is the formation of a transient ionic complex through triplet excimer of aromatic hydrocarbon or, when an electron acceptor is present, through triplet exciplex. The attack of cyanide ion on the transient complex yields the cyanated radical, ArHCN˙, which in aqueous acetonitrile reacts with itself to yield cyano- and dihydrocyano-products or, in dry acetonitrile after being attacked by an electron, is oxidized to the cyano-product. The rate constants for the formation of radical ions and the attack of cyanide ion are calculated from the experimental results.