Dehalogenation reactions of vicinal dihalides. Part IV. Kinetics of amine-promoted eliminations of 1-chloro-2-iodo-1,2-diphenylethane in aqueous dioxan

Abstract

The rate constants for the dehalogenation of 1-chloro-2-iodo-1,2-diphenylethane promoted by a series of amines have been determined in 60% dioxan. Pyridine reactivity follows a Brönsted relation with a slope β 0·29, which suggests little bond formation between the incoming nucleophile and iodine. Dehalogenation rates also correlate the stability constants of charge-transfer complexes between amines and iodine. The slope of this correlation is close to unity and this indicates that the charge distribution in the transition state of the dehalogenation reaction should be very similar to that of the charge-transfer complex.