Association/Hydrogen Bonding of Acetone in Polar and Non-polar Solvents: NMR and NIR Spectroscopic Investigations with Chemometrics

This paper reports H-1 NMR and NIR spectroscopic analysis of hydrogen bonding in acetone mixtures with water, CHCl3, CCl4, and CDCl3 with varying acetone concentrations (0-100 vol%). Spectroscopic data were chemometrically analyzed using independent component analysis to resolve the spectra of complexes existing in the solutions and to obtain their concentration profiles. Ab initio calculations provided additional information (hydrogen-bond energy and bond distance) about the investigated complexes. We have found that in addition to independent solvent associates, acetone-water mixtures contain three intermolecular complexes with acetone-water ratios of 1:1, 1:2 and 1:3. In less polar solvents with hydrogen or deuterium atoms (CDCl3, CHCl3), acetone does not generate self-associates and forms an intermolecular complex (1:1). In contrast, in aprotic non-polar carbon tetrachloride (CCl4) solutions, where no hydrogen-bonding is possible, self-association (as mentioned above for water-acetone mixtures) of two acetone molecules is preferred. The combination of spectroscopic techniques (H-1 NMR, NIR) with chemometric modeling and ab initio calculations leads to a better understanding of concentration dependent changes in the structure of acetone solutions. The approach discussed can be used for investigation of hydrogen-bonded interactions in other mixed solvents.