Radical Addition Rate Constants to Acrylates and Oxygen:  α-Hydroxy and α-Amino Radicals Produced by Photolysis of Photoinitiators

Laser flash photolysis of α-hydroxy and α-amino ketones, which are used as photoinitiators in free radical polymerization, lead to the generation of a series of nucleophilic α-hydroxy and α-amino radicals. Absolute addition rate constants of these radicals to n -butylacrylate and oxygen were measured by laser flash photolysis employing an indirect probe technique. Crystal violet and N,N ‘-bis(2,5-di- tert -butylphenyl)-3,4,9,10-perylenedicarboximide were used as selective probe molecules for these nucleophilic initiator radicals to measure the addition rate constants to n -butylacrylate and oxygen, respectively. High acrylate addition rate constants of some initiator radicals were found in acetonitrile solution, e.g., dimethylketyl radical ( k acrylate = 1.3 × 10 7 M - 1 s - 1 ) and 2-morpholino propan-2-yl radical ( k acrylate = 2.9 × 10 7 M - 1 s - 1 ).