Infrared study of 1,3-dimethyl-2-imidazolidinone in various solvents

Bulk dielectric effects of the solutions are attributed to the gradual decrease in the nu C=O frequency for 1,3-dimethyl-2-oxazolidinone (DMI) as the mole % CCl4/n-C6H14, CHCl3/n-C6H14, or CHCl3/CCl4 is increased. Intermolecular hydrogen bonding of the Cl3CH proton with DMI, or dipolar interaction of the chlorine atoms of CCl4 with the carbonyl carbon atom both cause the nu C=O mode to shift to lower frequency. The IR data indicate that the complexes formed with DMI in solution are comparable to those formed with tetramethylurea (TMU). The composition of the complexes changes as the mole % of the solvent system changes, and it appears as though these complexes form clusters with more than one type of cluster existing at a particular mole % solvent system. The decrease in the N-C-N bond angle for DMI compared to TMU is the major factor in causing nu C=O for DMI to vibrate at a higher frequency than nu C=O for TMU. DMI in alkyl alcohols also forms clusters where DMI is not intermolecularly hydrogen bonded with intermolecularly hydrogen bonded alkyl alcohols and the minority of these clusters exist where DMI is intermolecularly hydrogen bonded with intermolecularly hydrogen bonded alkyl alcohols. The solvent acceptor numbers (AN) are not found to be universally applicable to predict IR group frequencies, since these AN values do not take into account steric parameters of the solute and solvent.