Electronic Absorption Spectrum and Dissociation Energy of the Allyl Radical

Abstract

A system of diffuse bands in the region 3700–4100 Å has been observed during the flash photolysis of allyl bromide and eight other allyl compounds. The bands are found to be shifted when a sample of allyl‐d 5 bromide is used. The new band system with the (0–0) band at 4083 Å is assigned to the allyl radical [Complex chemical formula]. The diffuseness of the bands is attributed to predissociation of the radical in the excited state and gives an upper limit of 70.0 kcal/mole (≡3.04 eV) for the dissociation energy of the radical.