Electronic absorption spectrum and dissociation energy of the allyl radical

Abstract

A system of diffuse bands in the region 3700-4100 A 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-d5 bromide is used. The new band system with the (0-0) band at 4083 A is assigned to the allyl radical (CH2CH-CH2). 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.