FTIR study of hydrogen bonding of stearic acid with ethanol, dimethyl sulfoxide,and acetonitrile in supercritical CO_2

FTIR spectroscopy was used to study the hydrogen bonding of stearic acid with ethanol, dimethyl sulfoxide (DMSO), and acetonitrile in supercritical CO₂ at 318. 15 K, and 12.5 and 16.5 MPa. The concentration of the cosolvents range from 0–0.6 mol·L^?1. The area percentage of absorption bands for hydrogen-bonded and nonhydrogen-bonded species was Obtained from the IR spectra. The acid and the cosolvents can form hydrogen bond even when their concentrations a very low. At fixed solute concentration, the extent of hydrogen bonding increases with cosolvent concentration. At higher ethanol concentrations, it seems that one stearic acid molecule can hydrogen bond with more than one ethanol molecules simultaneously. It is seen that the strength of the hydrogen bond formed by the acid and the cosolvents is in the order: DMSO ethanol acetonitrile.