M. Tanabe, H. Takeuchi, S. Konaka
Dec 10, 1993
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Influential Citations
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Journal
Journal of Molecular Structure
Abstract
Abstract The molecular structure of 2,5-dimethylthiophene has been determined by gas electron diffraction. Ab initio SCF calculations at the 3-21G* level were carried out and used as an aid to the analysis. The torsional vibrations of two methyl groups were treated as large-amplitude motions. A CH Me bond was found to be cis with respect to the SC bond in the equilibrium structure and the three-fold potential barrier was determined to be 1.0(7) kcal mol −1 . The structural parameter values with estimated error limits (3σ) in parentheses are as follows: r g (SC) = 1.736(2) A, r g (CC) = 1.372(4) A, r g (CC Me ) = 1.510(5) A, r g (CH ring ) = 1.098(6) A, r g (CH Me ) = 1.112 A, ∠ α CSC = 92.6(5)°, ∠ α SCC ring = 110.7(5)°, ∠ α SCC Me = 121.6(4)°, ∠ α CCH = 123.4° and 〈∠ α HCH〉 = 108.1°, where 〈〉 denotes the average value. The values of r (CH Me ) − r (CH ring ), ∠CCH and 〈∠HCH〉 were taken from the 3-21G* calculations.