X-ray diffraction study of liquid neopentane and tertiary butyl alcohol

Abstract

The X-ray scattering functions for neopentane (CMe₄) at —17, 25 and 150 °C, and tertiary butyl alcohol (CMe₃OH) at 26 °C have been measured. These data have been analysed to obtain intramolecular structures, and by Fourier inversion to obtain an average nearest neighbour hydrogen-bonded oxygen–oxygen separation distance of 2.75 Å in CMe₃OH and methyl–methyl separation distances of 4.0 and 3.73 Å in CMe₄ and CMe₃OH, respectively. The data are also studied using the reference interaction site model (RISM). By fitting a five-centre fused hard-sphere model to the neopentane data, we obtain estimates for the Me–Me, Me–C and C–C correlation functions and the molecular coordination number. Also, by comparing RISM predictions with the results of a Monte Carlo study, we obtain some insight into the accuracy of RISM theory for fused sphere molecules. Finally, we find that it is not possible to fit the tertiary butyl alcohol data to a five-centre reference interaction site model.