Reaction of <i>tert</i>-Alkoxyl and Alkyl Radicals with Styrene Studied by the Nitroxide Radical-Trapping Technique
作者:Tomoyuki Nakamura、W. Ken Busfield、Ian D. Jenkins、Ezio Rizzardo、San H. Thang、Shuji Suyama
DOI:10.1021/jo9707489
日期:1997.8.1
The reactions of tert-alkyl peroxypivalates 1 (R = methyl, ethyl, and n-propyl) with styrene in the presence of the free-radical scavenger (1,1,3,3-tetramethyl-2,3-dihydro-1H-isoindol-2-yl)oxyl (2) have been studied at 60 degrees C, tert-Butyl and tert-alkoxyl radicals (tert-butoxyl, tert-pentyloxyl, and tert-hexyloxyl radicals) were generated from the thermolysis of 1, and the derivative alkyl radicals (methyl, ethyl, n-propyl, and 4-hydroxy-4-methylpentyl radicals) were formed by subsequent unimolecular reactions (beta-scission and 1,5-H shift) of the corresponding tert-alkoxyl radicals. The extent of the unimolecular reactions of the tert-alkoxyl radicals (versus addition to styrene) and the relative reactivity of alkyl radicals toward addition to styrene were obtained fi om the competitive addition/trapping reactions. The absolute rate constants for the addition of tert-butyl, ethyl, methyl, and n-propyl radicals to styrene at 60 degrees C were estimated to be (7.4, 4.7, 5, and 5.4) x 10(5) M-1 s(-1), respectively.