ABSOLUTE RATE CONSTANTS FOR IMINYL RADICAL REACTIONS

The kinetics of cyclization of the 2-methyl-6,6-diphenyl-5-hexeniminyl radical (3) were measured by laser flash photolysis methods from 0 to 50 degrees C, and the kinetics of trapping of radical 3 by thiophenol and p-chlorothiophenol were determined between 4 and 83 degrees C by indirect methods using the unimolecular rate constants as the basis va lues. Radical 3 cyclizes with a rate constant of 2.2 x 10(6) s(-1) at 25 degrees C and reacts with thiophenol and p-chlorothiophenol at this temperature with rate constants of 0.6 and 1.4 x 10(7) M(-1) s(-1), r espectively. Bu(3)SnH reacted with 3 too slowly to prevent nearly comp lete cyclization, but a crude rate constant for the trapping reaction was estimated. The cyclization and trapping reactions of iminyl radica l 3 are slower than the corresponding reactions of alkyl radicals.