Influence of intramolecular hydrogen bond strength on OH-stretching overtones.
Vapor-phase OH-stretching overtone spectra of 1,3-propanediol and 1,4-butanediol were recorded and compared to the spectra of ethylene glycol to investigate the effect of increased intramolecular hydrogen bond strength on OH-stretching overtone transitions. The spectra were recorded with laser photoacoustic spectroscopy in the second and third OH-stretching overtone regions. The room-temperature spectra of each molecule are dominated by two conformers that show intramolecular hydrogen bonding. Anharmonic oscillator local-mode calculations of the OH-stretching transitions have been performed to aid assignment of the different conformers in the spectra and to illustrate the effect of the intramolecular hydrogen bonding. The hydrogen bond strength increases in the order ethylene glycol, 1,3-propanediol, and 1,4-butanediol. The overtone transitions of the hydrogen-bonded hydroxyl groups are more difficult to observe with increasing intramolecular hydrogen bond strength. We suggest that the bandwidth of these transitions increases with increasing hydrogen bond strength and with increasing overtone and furthermore that these changes are in part responsible for the lack of observed overtone spectra for complexes.
Howard
Daryl L
DL
Department of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand.
Kjaergaard
Henrik G
HG
D002072:Butylene Glycols / Q000737:chemistry*; D019855:Ethylene Glycol / Q000737:chemistry*; D006860:Hydrogen Bonding; D006878:Hydroxides / Q000737:chemistry*; D011409:Propylene Glycols / Q000737:chemistry*; D011789:Quantum Theory; D012680:Sensitivity and Specificity; D013055:Spectrophotometry, Infrared / Q000379:methods; D014732:Vibration
D002072:Butylene Glycols; D006878:Hydroxides; D011409:Propylene Glycols; C041787:1,3-propanediol; C039681:1,4-butanediol; C031356:hydroxide ion; D019855:Ethylene Glycol