Discrimination of rotamers of aryl alcohol homologues by infrared-ultraviolet double-resonance spectroscopy in a supersonic jet

Infrared-ultraviolet double-resonance spectroscopy has been applied to discriminate rotamers of jet-cooled aryl alcohol homologues, phi-(CH2)(n)OH, where phi represents phenyl group and n = 1, 2, and 3 correspond to benzyl, phenethyl, and 3-phenylpropyl alcohols, respectively. Experimental results indicate that different OH stretching frequencies are associated with different rotamers and that the ability of intramolecular hydrogen bonding with the benzene pi-electron decreases with an increase in alkyl chain length. In each aryl alcohol, the most prominent species in jets corresponds to the non-hydrogen-bonded rotamer having higher OH stretching frequency.