Structure of 1-Propanol–Water Mixtures Investigated by Large-Angle X-ray Scattering Technique

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≤ 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.