LASER FLASH-PHOTOLYSIS STUDY OF CHLOROCARBENE

Laser flash photolysis (308 nm) of endo-7-chlorodibenzo[a,c]bicyclo[4. 1.0]heptane produces phenanthrene and chlorocarbene, which can be trap ped with pyridine to form an ylide. The ylide absorbs strongly at 374 nm, and its lifetime is many tens of microseconds. It was not possible to resolve the grow of the ylide due to the rapid reaction of chloroc arbene with solvent. It was possible, however, to deduce the lifetimes of chlorocarbene in various solvents by measuring the yield of ylide as a function of [pyridine] and assuming that the absolute rate consta nt of reaction of chlorocarbene is the average of those of dichlorocar bene and alkylchlorocarbenes, which have been previously reported. Abs olute rate constants for the reaction of chlorocarbene with alkenes we re then deduced by the Stern-Volmer method, and the relative reactivit y of chlorocarbene toward alkenes was found to be in good agreement wi th the relative reactivities of the lithium-chlorocarbene complex or c arbenoid determined by analysis of product mixtures reported by Closs and Schwartz.