On the reactivity of phosphonyl radicals towards olefinic compounds

Abstract

AbstractPhosphonyl radicals of the structure OṖR1 (R2) with R1 and R2: C6H5(1); C6H5, OCH(CH3)2(2); CH3, OCH3(4) and OC2H5(5) were generated by UV‐photolysis of appropriate acylphosphine oxides or acylphosphonates which are effective initiators of the free radical polymerization of olefinic compounds. All five radicals are very reactive towards monomers such as methacrylonitrile, styrene and methyl methacrylate (k = 5 · 107 to 2 · 108 1 · mol−1 · s−1), as was found by employing laser flash photolysis techniques. In the cases of acrylonitrile, methyl acrylate, butyl vinyl ether, and vinyl acetate k ranged from 106–107 1 · mol−1 · s−1. The high reactivity of the radicals 1 – 5 is due to their tetrahedral structure. The Q‐e scheme of Alfrey and Price proved useful to recognize trends in the dependence of k on the chemical nature of both phosphonyl radicals and monomers.