Collect. Czech. Chem. Commun. 1990, 55, 80-90

Infra-red and 35Cl nuclear quadrupole resonance studies of hydrogen bonded adducts of 2-chlorobenzoic acid derivatives

Jerzy Kalenika, Irena Majerza, Lucjan Sobczyka, Eugeniusz Grechb and Mustafa M. M. Habeebb

a Institute of Chemistry, University of Wrocław, 50-383 Wrocław, Poland
b Institute of Fundamental Chemistry, Technical University, 71-065 Szczecin, Poland


The IR and 35Cl NQR spectra of several solid hydrogen bonded adducts of o-chlorobenzoic acids and amines were studied over the broad ΔpKa range. Both IR and NQR spectra yield the indication of the existence of an inversion (critical) ΔpKa range where the proton transfer takes place. The critical point is distinguished by a deep minimum of the position of the gravity centre of the broad protonic band. The mechanism of the transmittance of the charge distribution within the hydrogen bridge on the electric field gradient in the position of quadrupole Cl nuclei attached to the phenyl ring is analysed.