Relative rate constants have been determined for the addition of phenyl and substituted phenyl radicals to styrene, methyl methacrylate, methyl acrylate, and methacrylonitrile, all relative to acrylonitrile. These data have been correlated with a0 constants for substituents in the radical by an expression in which the slope ( p~ -PAM) corresponds to the difference in polar response. These and other findings are discussed in terms of theories regarding reactivity in radical addition reactions and, particularly, with respect to a general treatment of such data based on studies of polymer radicals. (24) (a1 C. (25) Equation 16 in ref 3: a = -5.3~ where u is the usual substituent Soc., 65, 418 (1959). 68, 149 11961); Tran8. F a d a y Soc., 69, 530 (1963). constant for the ester group.718 DICKERMAN', DESOUZA, FRYD, MEGNA, AND SKOULTCHI The Journal of Organic Chemistry n 3 3 c o o 0 0 r r ) C r * 1 0 Y?"': m m o * 1010ww
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