Solvent sensitivity of the wavenumber characterising the carbonyl stretching vibration of N-cyclohexyl-2-pyrrolidinone dissolved in pure liquids and in mixtures formed by hexane and deuteriotrichloromethane at 298.2 K

Abstract

The dependence of (CO) on solvent for N-cyclohexyl-2-pyrrolidinone (NCP) as solute in 18 pure solvents can be described using a two-parameter equation based on the Taft–Kamlet π*(dipolarity/polarisability) and α proton donor parameters. In alcoholic solvents two bands are recorded, the band at the lower wavenumber following the correlation. When CDCl₃ is added to a solution of NCP in hexane, (CO) shifts to lower wavenumbers but over a range of mixture compositions two bands are also observed characteristic of the carbonyl group in NCP. The origin of these bands is discussed in terms of two types of hydrogen bonding together with their individual dependences on mixture composition. Comparisons are drawn with the solvent sensitivities of (CO) for propanone, cyclohexanone and dimethylacetamide.