Determination of Liquid Structures of the Primary Alcohols Methanol, Ethanol, 1-Propanol, 1-Butanol and 1-Octanol by X-ray Scattering

Four first primary alcohols and 1-octanol were studied with the wide-angle X-ray scattering method using both transmission and reflection techniques at room temperature (293 K). The subsequent radial distribution analysis gives C-O and C-C distances that are in good agreement with the known bond lengths of single alcohol molecules. The shortest averaged C-H and O-H distances are much smaller than those from the gas-phase data. It is deduced that the shortened distance is caused by the deformed electron distribution between H and C atoms. The intermolecular hydrogen bonding between hydroxyl groups occurs at a distance of 2.8 Å, and is a common feature for all the samples. The corresponding coordination number of 1.7 indicates linear chains of about ten molecules. The absence of sharp features in the intensity curves suggests that the arrangement of chains is irregular and that the length of the chains varies.