Relative Rates and Arrhenius Parameters for Selected 1,2-Arylmigrations and Five- and Six-Member Cyclizations of Ortho-Allybenzyl Radical from Reactions of Halides and Tri-N-Butyltin Hydride (Poster Session, 19TH Conference on Rea

摘要

The temperature dependent rates of radical rearrangements relative to abstraction of hydrogen atom from tri-n-butyltin hydride have been determined. The rearrangement of 2-phenyl-2-methylpropyl to 2-phenyl-1-methylpropyl (neophyl rearrangement) relative to hydrogen abstraction is represented by log r = 2.11 +- 0.02 - (7.35 +- 0.04)/theta, theta = 2.3 RT kcal/mole. The rearrangement of 0-allylbenzyl to 2-indanylmethyl exhibited log r = 2.52 +- 0.12 - (10.59 +- 0.25)/theta, and the rearrangement of 0-allylbenzyl to 2-tetralyl is represented by log r = 2.4 +- 0.2 - (11.6 +- 0.2)theta. The rearrangement of 1-indanylmethyl to 2-tetralyl is represented by log r = 2.24 +- 0.06 - (10.22 +- 0.11)/theta. The attempt to determine the cyclization rate of 0-vinyl-2-phenylethyl radical to 1-indanylmethyl and 1-tetralyl failed due to irreversible addition of tri-n-butyltin radical to the styrene double bond. However, kinetic closure to the five member ring was preferred over closure to the six member ring. From known or estimated rates of abstract of hydrogen from tri-n-butyltin hydride, rates or rearrangement of the three radicals are derived. (ERA citation 07:051020)