Keefe C Dale, Gillis Elizabeth A L, MacDonald Lisa
Department of Chemistry, Cape Breton University, Sydney, Nova Scotia, Canada, B1Y 6L2.
J Phys Chem A. 2009 Mar 19;113(11):2544-50. doi: 10.1021/jp8092034.
Fourier Transform infrared spectroscopy and Raman spectroscopy have been used to investigate hydrogen bonding of methanol in different solvents with an aim to explore potential experimental evidence for improper hydrogen bonding involving the methyl group of methanol as suggested by various computational studies. Pure methanol and solutions of methanol in water, acetonitrile, carbon tetrachloride, deuterium oxide, and deuterated acetonitrile have been studied over a range of concentrations. Wavenumber shifts of the CH stretching vibrations were examined to determine if the CH from methanol participates in hydrogen bonding. New concepts of the vibrational wavenumber and integrated intensity at infinite dilution are proposed and given the respective symbols nu(CH(o)) and C(j,CH)(o). Using the results obtained for methanol in carbon tetrachloride as a reference, shifts in nu(CH(o)) of methanol to higher wavenumbers (blue shifts) were observed in each of the other solvents studied, with the shifts being greatest for the methanol-water interactions. The shifts in vibrational wavenumber suggest possible improper hydrogen bonding, although at this stage a definitive conclusion is not possible. The C(j,CH)(o) results show that there is no distinguishable change in the methanol CH stretch integrated intensity in carbon tetrachloride and acetonitrile, while there is a significant decrease in the methanol CH stretch integrated intensity in the water solutions.
傅里叶变换红外光谱和拉曼光谱已被用于研究甲醇在不同溶剂中的氢键，目的是探索各种计算研究提出的涉及甲醇甲基的不当氢键的潜在实验证据。研究了纯甲醇以及甲醇在水、乙腈、四氯化碳、重水和氘代乙腈中的溶液在一系列浓度范围内的情况。检查了CH伸缩振动的波数位移，以确定甲醇中的CH是否参与氢键。提出了无限稀释时振动波数和积分强度的新概念，并分别给出符号ν(CH(ο))和C(j,CH)(ο)。以甲醇在四氯化碳中的结果为参考，在所研究的其他每种溶剂中都观察到甲醇的ν(CH(ο))向更高波数的位移（蓝移），其中甲醇 - 水相互作用的位移最大。振动波数的位移表明可能存在不当氢键，尽管在此阶段还无法得出明确结论。C(j,CH)(ο)结果表明，甲醇在四氯化碳和乙腈中的CH伸缩积分强度没有明显变化，而在水溶液中甲醇的CH伸缩积分强度则显著降低。
