Structure and conformation of 1,3-dithlane: an electron diffraction study |
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Authors: | Wade J Adams LS Bartell |
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Institution: | 1. Department of Chemistry, The University of Michigan, Ann Arbor, Mich. 48109 U.S.A.;2. Department of Chemistry, Western Michigan University, Kalamazoo, Mich. 49008 U.S.A. |
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Abstract: | A gas-phase electron diffraction study of 1,3-dithiane, carried out at 100° C, has found no statistically significant evidence for the presence of any conformer in the vapor other than the chair, within an estimated uncertainty of 10%. An index of the degree of ring puckering in 1,3-dithiane is the average torsional angle which was found to be 61.3°, appreciably greater than that in cyclohexane, but somewhat less than that in 1,4-dithiane and 1,3,5-trithianc. The C-C-C, C-C-S and S-C-S valency angles, 113.6(33)°, 114.9(4)° and 115.0(3)° respectively, were all larger than the C-C-C valency angles in cyclohexane. The C-S-C valency angle, 98.1(7)°, was slightly smaller than that of dimethyl sulfide. Observed bond lengths were rg(C-H) = 1.116(10) Å, rg(C-H) = 1.533(5)Å, and rg(C-S) = 1. 812(3)Å and mean amplitudes of vibration were lg(C-H) = 0.081(12)Å, lg(C-C) = 0.052(6)Å and lg(C-S) = 0.052(4) Å (parenthesized quantities correspond to 3σ). Curiously, nonbonded distances between the axial hydrogen atoms in 1,3-dithiane are virtually identical to those in cyclohexane, even though these molecules have greatly different bond lengths, valency angles, and torsional angles. |
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