Determination of the hydrogen‐bond basicity of weak and multifunctional bases: the case of lindane (γ‐hexachlorocyclohexane)

Abstract

AbstractWe made use of four methods for determining the hydrogen‐bond (HB) basicity of lindane (γ‐hexachlorocyclohexane): (i) experimental Fourier transform IR measurement of a sum of individual 1:1 equilibrium constants for the formation of 1:1 4‐fluorophenol‐lindane hydrogen‐bonded complexes in CCl4; (ii) calculation of the overall HB basicity from octanol–water partition coefficients; (iii) correlation of the HB basicity of chloroalkanes with the electrostatic potentials around chlorine atoms; and (iv) correlation of the HB basicity of chloroalkanes with the computed enthalpy of their complexes with hydrogen fluoride. It is consistently found that lindane remains a weak HB base because multifunctionality cannot fully compensate for the electron‐withdrawing inductive effects that chlorine atoms exert over one another. Actually, only five chlorine atoms behave as HB acceptors, one axial chlorine being deactivated by inductive effects. Stereoelectronic effects lead to the formation of three‐centered hydrogen bonds. Copyright © 2003 John Wiley & Sons, Ltd.