Intermolecular Forces and O—H Absorption Bands in Alcohols at 3

THE liquid aliphatic alcohols show in the region of 3 two C-H bands, 2870–2890 cm.1 and 2950–5970 cm.1, and a very large and intense band at about 3350 cm.1, which is generally attributed to a fundamental O-H vibration. If we dilute to a very small concentration, we observe for ethyl alcohol in carbon tetrachloride that, at normal temperature, in passing from a concentration of 3.33 mol/lit. to 0.005 mol/lit. and keeping the product concentration by thickness constant, the C-H bands retain their intensity, whereas the large O-H band, which absorbed 90 per cent, disappeared completely at a concentration of 0.02 mol/lit. A new narrow and well-defined band appears then at 3640 cm.1, and its intensity grows with dilution. The molar extinction coefficient passes from 4, for a concentration 0.05 mol/lit., to 15 for a concentration 0.005, instead of remaining constant. The results for alcohol carbon disulphide are in complete agreement with those mentioned above.