Rapid chloride-exchange reactions of organosilicon and organogermanium chlorides

Publisher Website
Google Scholar
Abstract
The kinetics of the 36Cl–-exchange reaction of a number of labile organo-silicon and -germanium chlorides of the type R3MCl have been studied in acetone–dioxan mixture with the aid of an automated flow–quench system. The reactivity of all substrates decreases with increasing length of the alkyl chain; steric effects are more important in the reactions with silicon chlorides than with those of germanium. Benzyl- and 2-phenylethyl-substituents show an unexpectedly high reactivity. The kinetic order in the carrier salt, Li36Cl, is one half for R = n-butyl and cyclohexyl (M = Si) and R = phenyl (M = Ge) but for 2-phenylethyl and benzyl the order is unity: these orders are accounted for in terms of the relative reactivities of ion pairs and free ions. Activation parameters indicate a lower activation enthalpy but more negative entropy for germanium as compared with silicon. Racemization and exchange studies in this solvent strongly support an associative mechanism for the chloride-exchange reaction.

This publication has 0 references indexed in Scilit: