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.
Ma
Xiaoyan
X
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.
Wang
Jianping
J
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