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The structure of aqueous alcohol solutions at the molecular level for many decades has remained an intriguing topic in numerous theoretical and practical investigations. The aberrant thermodynamic properties of water-alcohol mixtures are believed to be caused by the differences in energy of hydrogen bonding between water-water, alcohol-alcohol, and alcohol-water molecules. We present the Raman scattering spectra of water, ethanol, and water-ethanol solutions with 20 and 70 vol % of ethanol thoroughly measured and analyzed at temperatures varying from -10 to +70 °C. Application of the MCR-ALS method allowed for each spectrum to extract contributions of molecules with different strengths of hydrogen bonding. The energy (enthalpy) of formation/weakening of hydrogen bonds was calculated using the slope of Van't Hoff plot. The energy of hydrogen bonding in 20 vol % of ethanol was found the highest among all the samples. This finding further supports appearance of clathrate-like structures in water-ethanol solutions with concentrations around 20 vol % of ethanol.

Although vodka is a reasonably pure mixture of alcohol and water, beverage drinks typically show differences in appeal among brands. The question immediately arises as to the molecular basis, if any, of vodka taste perception. This study shows that commercial vodkas differ measurably from ethanol-water solutions. Specifically, differences in hydrogen-bonding strength among vodkas are observed by (1)H NMR, FT-IR, and Raman spectroscopy. Component analysis of the FT-IR and Raman data reveals a water-rich hydrate of composition E x (5.3 +/- 0.1)H(2)O prevalent in both vodka and water-ethanol solutions. This composition is close to that of a clathrate-hydrate observed at low temperature, implying a cage-like morphology. A structurability parameter (SP) is defined by the concentration of the E x (5.3 +/- 0.1)H(2)O hydrate compared to pure ethanol-water at the same alcohol content. SP thus measures the deviation of vodka from "clean" ethanol-water solutions. SP quantifies the effect of a variety of trace compounds present in vodka. It is argued that the hydrate structure E x (5.3 +/- 0.1)H(2)O and its content are related to the perception of vodka.

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The secondary coordination sphere contributes to the stability of complexes, the extraction behaviour of the reagents and europium phosphorescence lifetimes.