Free radical chain reactions of chlorine with cyclobutane in the solid state: Evidence for radical migration via H atom transfer

Abstract

The laser-initiated reaction of chlorine with cyclobutane, deposited as a thin amorphous film at 77 K, is found to produce exclusively chlorocyclobutane and HC1 via a free radical chain mechanism. The reactions are initiated by pulsed laser photolysis of molecular chlorine at 308 nm. Product formation is monitored by Fourier transform infrared absorption spectroscopy. The quantum yield for reaction increases from 1.1±0.3 in an equimolar mixture to a yield of 7.4±0.8 for mixtures rich in cyclobutane. These results are consistent with a reaction mechanism which involves the transfer of a hydrogen atom from cyclobutane to cyclobutyl radical, permitting the radical site to propagate freely in the solid.