Cα−H Bond-Stretching Frequency in Alcohols as a Probe of Hydrogen-Bonding Strength: A Combined Vibrational Spectroscopic and Theoretical Study of n-[1-D]Propanol

Abstract

The sensitivity of the νCα-H/D vibrational stretching frequency to hydrogen bonding in alcohols is examined by infrared and Raman spectroscopy, supported by DFT(B3LYP)/6-311++G(d,p) calculations. The model compound studied is (R,S)-n-[1-D]propanol. It is shown that the νCα-H/D mode can be successfully correlated with the hydrogen-bond strength in a given solvent, provided the O−H group involved in the hydrogen bond is not acting simultaneously as a hydrogen-bond donor and acceptor. In addition, a detailed analysis of the spectroscopic features observed in both the νO-H and νCα-H/D spectral regions of the spectra of n-propanol and (R,S)-n-[1-D]propanol, in a series of different experimental conditions, which include the matrix-isolated compound (in argon matrix), pure liquid and low-temperature glassy states, and solution in different solvents, is undertaken. This permits the contribution of the different conformers of the studied compounds to be assigned to the bands observed in the νO-H and νC-H spectral regions.