PHOTOCHEMICAL REACTIONS OF ARENECARBONITRILES WITH ALIPHATIC AMINES. 2. EFFECT OF AMINE STRUCTURE ON AMINYL VS. alpha -AMINOALKYL RADICAL FORMATION.

Article abstract of DOI:10.1021/ja00313a039

The photochemical reactions of 9-phenanthrenecarbonitrile with several secondary and primary amines and triethylamine have been investigated. Rate constants for fluorescence quenching by secondary and primary amines decrease with amine alpha -alkylation in spite of increased electron-donor ability of the more substituted amines. This trend is attributed to a steric effect on the equilibrium constant for reversible exciplex formation. The reactions of secondary and primary amines in nonpolar solvent result in selective N-H vs. alpha C-H transfer from amine to arene, via a singlet exciplex. The ratio of alpha -C-H/N-H transfer increases with alpha -alkylation and increased solvent polarity and is larger for secondary vs. primary amines.