Differentiating subtle variation of weak intramolecular hydrogen bond in vicinal diols by linear infrared spectroscopy.
Linear IR spectra show "free" and intramolecular hydrogen-bonded (IHB) -OH groups in vicinal diols as two separate O-H stretching absorption bands. Here we present a case study of four linear vicinal diols with different alkyl groups: 1,2-ethylene glycol, 1,2-propanediol, 2,3-butanediol, and 1,2-butanediol. By carefully removing contributions from anharmonic vibrational coupling and local structural effect, "pure" IHB-resulted frequency separation and peak enhancement are obtained and found to exhibit a linear relationship between them. The results suggest that the IHB formation energy in the diols is structurally dependent, and 1,2-propanediol has the smallest vibrational contribution to the IHB energy among the four diols examined.
Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China.
Xiaoyan
X
Ma
Jianping
J
Wang
D000438:Alcohols / Q000737:chemistry*; D006860:Hydrogen Bonding; D006878:Hydroxides / Q000737:chemistry; D008958:Models, Molecular; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared; D013816:Thermodynamics; D014732:Vibration
D000438:Alcohols; D006878:Hydroxides; C031356:hydroxide ion