The C–H···Cl hydrogen bond: does it exist?

Abstract

The extensive occurrence of C–H···Cl hydrogen bonds has been established through a systematic statistical analysis of the Cambridge Crystallographic Database; chloride anions are shown to be better hydrogen-bond accepor systems than neutral chloride-containing molecules, and a similar situation pertains for the other halides. As a result of this study, we propose that the conceptual van der Waals cut-off criterion be dropped for establishing the presence of weak intermolecular and intramolecular interactions, and be replaced by a distance/angle criterion determined by the empirical approach outlined here.