Large-angle X-ray scattering investigation of the structure of 2-propanol-water mixtures

The structure of 2-propanol and its aqueous Mixtures has been investigated at 25 degreesC, using a large-an-le X-ray scattering (LAXS) technique. The total radial distribution function of neat 2-propanol has shown that hydrogen-bonded chains of 2-propanol molecules are formed. In the 2-propanol-water mixtures, 2-propanol chains predominate at mole fractions x(2pr) > similar to0.1. When x(2pr) decreases from x(2pr) = 1, the number of hydrogen bonds reaches a plateau of 3.4 +/- 0.1 at x(2pr) less than or equal to similar to0.1, suggesting that the tetrahedral-like structure of water is mainly formed. On the basis of the present findings, together with previous results on in ethanol-water and ethanol-water mixtures, effects of hydrophobic groups on the structure of the alcohol-water mixtures are discussed. The heat of mixing at 25 degreesC as a function of has been interpreted in terms of the structural transition of solvent clusters.