FTIR spectral study of double cyclic intermolecular hydrogen bonding in glutaric acids

Abstract

The concentration dependence of the FTIR spectra of glutaric acid 1, 3-methylglutaric acid 2 and 3,3-dimethylglutaric acid 3 has been measured in CCl₄ solution. In these compounds, double cyclic intermolecular hydrogen-bonded dimers involving a 16-membered ring are formed between the molecules, in which the two carboxy groups are approximately in parallel alignment with each other. The percentage (h) of these dimers at 3 × 10^–5 mol dm^–3 in dilute CCl₄ solution has high values of 73% for 1, 85% for 2 and 44% for 3. The association constant is 7.7 × 10⁴ dm³ mol^–1 for 2. Conformational analysis of compound 1 has been carried out by the ab initio MO method at the 3-21 G(*) level.