Torsional interaction in 2-haloethanols: infrared data,ab initio results and treatment of a two-dimensional model |
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Authors: | R Meyer Matti Perttilä |
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Institution: | Laboratorium für Physikalische Chemie, Eidgenössische Technische Hochschule, Universitätsstrasse 22, CH-8092 ZürichSwitzerland;Department of Physical Chemistry, University of Helsinki, Meritullinkatu 1C, SF-00170 Helsinki 17 Finland |
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Abstract: | The splittings of the hydroxyl torsional absorption bands observed in the gas phase IR spectra of 2-haloethanols, XCH2-CH2-OH are reported for X = Cl, Br, I. The satellite absorptions, assigned to excited states of the skeletal torsion, appear on the low-frequency side of the fundamental, possibly because of weakening of the internal hydrogen bond. The torsional potential surface is investigated by calculations using a two-dimensional model based on the known experimental data for the compound with X = Cl, and by ab initio calculations for the haloethanols with X = F and X = Cl. Models based on the assumption of pure torsion and simple dipole-dipole or central force interaction terms failed to reproduce the observed data for 2-chloroethanol, but good agreement was obtained after local modification of the potential surface interpolated from the ab initio calculations. The results may help devise the phenomenological theory of potential energy needed for quantitative study of the internal hydrogen bond. |
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Keywords: | Present address: Institute of Marine Research PL 166 SF-00141 Helsinki 14 Finland |
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