Infrared study of the interaction between carbonyl bases and HCl or HBr

Abstract

The interaction between carbonyl bases (benzophenone, acetophenone and cyclohexanone) and HCl or HBr has been studied by infrared spectrometry in the 3500 - 800 cm⁻¹ range. In carbontetrachloride, the four studied bases form with HCl normal hydrogen bonds of 1:1 and 1:2 (one base - two acids) stoichiometry. This is also the case for the adducts of benzophenone and acetophenone with HBr. The formation constants are reported. For the interaction between acetone and HBr, the concentration of protonated species seems to be very weak. The interaction between cyclohexanone and HBr leads to complexes of 1:1 and 2:1 (two bases - 1 acid) stoichiometry. The appearance in the spectrum of a broad absorption band between 1500 and 800 cm⁻¹ suggests the formation of nearly symmetrical (OHO)⁺ hydrogen bonds. The infrared spectra in dichloromethane and in binary solution are also discussed.