REACTION OF TERT-ALKOXYL AND ALKYL RADICALS WITH STYRENE STUDIED BY THE NITROXIDE RADICAL-TRAPPING TECHNIQUE

The reactions of tert-alkyl peroxypivalates 1 (R = methyl, ethyl, and n-propyl) with styrene in the presence of the free-radical scavenger , 3,3-tetramethyl-2,3-dihydro-1H-isoindol-2-yl)oxyl (2) have been studie d 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 subsequ ent unimolecular reactions (beta-scission and 1,5-H shift) of the corr esponding tert-alkoxyl radicals. The extent of the unimolecular reacti ons 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 absolu te 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.