Directive effects in benzylic hydrogen atom abstraction. Part VI. Halogenation of arethyl fluorides

Abstract

The relative rates of halogenation of XC₆H₄CH₂CH₂F with N-bromosuccinimide in CCI₄ at 80° and with sulphuryl chloride in benzene at 40° are correlated by the Hammett equation to give ρ+–1·43 (r0·996) and ρ–0·96 (r0·985), respectively. The different nature of the transition states of atomic bromine and the benzene-complexed chlorine atom with the substrates XC₆H₄CH₂Y previously noted has been consistently observed. Deuterium isotope effects in the N-bromosuccinimide bromination of PhCHDY and PhCD₂Y have been measured for Y = Ph, CH₂Cl, CH₂F, and Cl and these values are related to the relative reactivity of the undeuteriated compounds.