The irreversible addition of alkyl radicals to diethyl vinylphosphonate to give the α-phosphorylalkyl radicals (1) has been studied by e.s.r. spectroscopy at 233 K in hydrocarbon solvents. The rate constants for addition (kadd) have R·+ H2CCHP(O)(OEt)2 [graphic omitted] RCH2ĊHP(O)(OEt)2(1) been determined relative to those (2kAt) for self-reaction of (1) for a series of addenda. The values of 2kAt have been measured in separate kinetic e.s.r. experiments for (1; R = Me)(2.0 × 109 dm3 mol–1 s–1) and (1; R = But)(5.0 × 108 dm3 mol–1 s–1) and thus absolute values of kadd were obtained. The rate constant kadd increases along the series R·= Me·(2.5 × 103 dm3 mol–1 s–1) < Rprim· < Rsec· < But·(5.9 × 104 dm3 mol–1 s–1) and this order is interpreted in terms of the over-riding importance of polar effects in determining the size of the barrier for addition of these nucleophilic radicals to the electron deficient alkene.
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Baban et al. (1981) studied this question.