FTIR spectral study of hydrogen bonding in ω-alkanedicarboxylic acids in dilute CCl4 solution

Abstract

FTIR spectra of the title compounds, HO₂C(CH₂)_nCO₂H (n= 4–14)2–12, were measured in dilute CCl₄ solution. For compounds 2–7, double cyclic intermolecular hydrogen bonds (II) similar to those observed for glutaric acid 1 were found between the carboxy groups, while 8–12 had cyclic intramolecular hydrogen bonds (IVb). A zigzag correlation was found between the percentage (h) of the double cyclic intermolecular hydrogen-bonded molecules and the n value. The h values of odd-membered compounds were larger than those of even-membered ones and the latter values increased with increasing n value. The h value for 7(n= 9), which forms a 28-membered ring, was 82%. The percentages of the cyclic intramolecular hydrogen-bonded molecules showed the high value of 97% for 12(n= 14). Conformational analyses on compounds 1–12 were carried out using the AM1 method. The hydrogen bondings observed in solution are discussed on the basis of the results.