The molecular structure of p-benzenedithiol has been investigated by gas-phase electron diffraction. Least-squares refinement of a molecular model with C2h symmetry, containing a C6H4S2 core of D2h symmetry, has led to the accurate determination of the following bond distances and angles: 〈rg(C-C)〉 = 1.399 ± 0.003Å, ∠C-C(SH)-C = 120.1 ± 0.2°, rg(C-S) = 1.775 ± 0.004Å. The difference in length between the Cipsg-Cortho bonds and the central C-C bonds of the benzene ring is barely significant, 0.005 ± 0.005 A. An important result of the present study is that the SH substituent, unlike the majority of common functional groups, does not cause measurable distortions of the carbon skeleton of the benzene ring. The geometrical parameters of the substituent are rg(S-H) = 1.359 ± 0.011 Å and ∠C-S-H = 96.5 ± 2.0°. Refinement of a non-planar molecular model indicates that large torsions of the thiol groups about their respective C-S bonds, leading to an average twist angle as large as 30°, are not incompatible with the electron diffraction data.
ASJC Scopus subject areas
- Condensed Matter Physics
- Physical and Theoretical Chemistry