Carbonyl stretching frequency characteristics for the strongly hydrophobic solute, N-cyclohexyl-2-pyrrolidone in binary aqueous mixtures at 298.15 K. Evidence for a two-domain model for 2-butoxyethanol–water mixtures

Abstract

Infrared spectra are reported in the CO stretching region for N-cyclohexyl-2-pyrrolidone (NCP) in D₂O as a function of the mole fraction of added cosolvents. As the solvent composition is changed by adding methanol, ethanol and 2-methylpropan-2-ol, the spectra reveal the presence of two types of hydrogen bonding to the carbonyl group of NCP. When cyanomethane is added, the spectra also show the formation of non-hydrogenbonded NCP in MeCN-rich mixtures. When 2-butoxyethanol is added to NCP in D₂O, the patterns generated by the plots showing the relative amounts of solvates change characteristically in the D₂O-rich mixtures consistent with the presence of alcohol-rich and D₂O-rich domains.