Structure of 1-propanol-water mixtures investigated by large-angle X-ray scattering technique

摘要

Large-angle X-ray Scattering (LAXS) experiments at 298 K have been made on 1-propanol - water mixtures over the whole 1-propanol mole fraction range. The radial distribution functions show that the predominant clusters in 1-propanol-water mixtures change at 1-propanol mole fraction x(1pr) = 0.1; the tetrahedral-like structure of water is mainly formed in the mixtures with x(1pr) less than or equal to 0.1, while hydrogen-bonded chain clusters of 1-propanol molecules predominate in the mixtures at x(1pr) > 0.1. From the present results, together with the previous ones on methanol - water, ethanol - water, and 2-propanol-water mixtures, size and shape effects of the hydrophobic groups on the structure of aliphatic alcohol - water mixtures are discussed at the molecular level. The anomalies of the enthalpies of mixing for 1-propanol - water mixtures at 298 K are interpreted on the basis of the proposed change in structure of the mixtures with 1-propanol mole fraction.