Investigation of the hydrogen bonding in chlorocarboxylate anions using 35Cl quadrupole resonance spectroscopy

Abstract

³⁵ Cl quadrupole resonance frequencies have been measured in a wide range of normal and acid salts of chlorocarboxylic and chlorobenzoic acids. The multiplicity of ³⁵Cl signals and the shifts of the ³⁵Cl frequencies on deuteriation of the acid proton in salts containing the anion [RCO₂‥ H ‥ CO₂R]^– have been used to establish the symmetry of the hydrogen bond. The observed deuteriation shifts can be as large as 0.9 % of the ³⁵Cl frequency in asymmetric hydrogen bonds; they are negligibly small if the hydrogen bond is symmetric.