Molecular structure and ring distortions of p-dichlorobenzene as determined by electron diffraction

György Schultz, I. Hargittai, Aldo Domenicano

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Abstract

The molecular structure of p-dichlorobenzene in the vapour phase has been studied by electron diffraction. Least-squares refinement of a model with D2h symmetry has led to the accurate determination of the small deviations of the benzene ring from D6h symmetry caused by the chlorine substituents. The most appreciable effect is an increase from 120° to 121.6 ± 0.2° of the internal angle at the ipso carbon, associated with a shortening of the distance between the two ipso atoms. A less pronounced effect is a shortening of the C-C bonds that originate from the ipso carbons as compared to the central C-C bonds (rg = 139.0 ± 0.3 pm vs. 139.5 ± 0.4 pm). Other bond distances are rg (C-Cl) - 173.0 ± 0.4 pm and rg (C-H) = 109.4 ± 1.0 pm. The observed ring distortions are in agreement with those obtained by low-temperature X-ray crystallography on three different crystal phases of p-dichlorobenzene. They are also consistent with those obtained for chloro-benzene by gas-phase electron diffraction and by NMR spectroscopy in a nematic solvent. The rs structure of chlorobenzene obtained in a recent study by micro-wave spectroscopy is shown to need revision, as far as the ipso region of the ring is concerned.

Original languageEnglish
Pages (from-to)281-292
Number of pages12
JournalJournal of Molecular Structure
Volume68
DOIs
Publication statusPublished - Jan 1 1980

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ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy
  • Organic Chemistry
  • Inorganic Chemistry

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