INVESTIGATION OF THE MOLECULAR-STRUCTURE OF CATECHOL BY COMBINED MICROWAVE SPECTROSCOPY AND ABINITIO CALCULATIONS

The molecular structure of catechol (1,2-dihydroxybenzene) was studied by microwave spectroscopy combined with ab initio geometry refinements of the 4-21G level, and 4-21G augmented with d-functions (4-21G*). It is shown that the experimental rotational constants of catechol can be reproduced by a geometry in which the CO bond lengths are 1.409 and 1.395 Å. This is in contrast to the results of a previous investigation [M. Onda,J. Mol. Struct., 159 (1987) 243] in which an exceedingly large difference of 0.08 Å between the two CO bonds was reported together with an unusually short CO bond length of 1.323 Å. In that investigation, the magnitude of the two CO bonds depended on assumptions made in the data analysis, but the difference between them was found to be definitive on the basis of statistical criteria. In order to obtain an updated correction for the 4-21G CC bonds, a new ro structure was refined for benzene (r(CC)=1.3974(3) Å. r(CH)=1.9788(16) Å) using recently reported data from Bauder [J. Mol. Struct., 190 (1988) 31]. © 1990.