Transient spectral and kinetic behaviors of carbonyl ylide photogenerated from 2,2-dicyano-3-(2-naphthyl)-oxirane

Abstract

On laser flash photolysis, by direct light absorption as well as under energy transfer sensitization by aromatic ketone triplets, 2,2-dicyano-3-(2-naphthyl)oxirane in fluid solutions forms an ylide characterized by broad and intense absorption spectra (λ max = 610 nm, ϵ max = 2.0 × 10 4 M −1 cm −1 in benzene) and unusually long lifetimes in aprotic solvents (τ Y = 130 μs in benzene). The ylide reacts with water, alcohols and dipolarophiles with rate constants that are atypically low (10 3 – 10 6 M −1 s −1). The reactivity follows a trend parallel to that of acidity of alcohols and opposite to that of electron-rich character of dipolarophiles.