Journal of Molecular Structure, 240 (1990) 95-110 Elsevier Science Publishers B.V., Amsterdam 95 zyxwvutsrq THE MOLECULAR STRUCTURE OF 1,2,3-TRICHLOROBENZENE DETERMINED BY COMBINED ANALYSIS OF DATA FROM GAS ELECTRON DIFFRACTION AND LIQUID CRYSTAL NMR AND BY X-RAY CRYSTALLOGRAPHY ALEXANDER J. BLAKE, RICHARD BLOM*, STEPHEN CRADOCK, SAMANTHA L. DAVIDSON and DAVID W.H. RANKIN Department of Chemistry, University of Edinburgh, West Mains Road, Edinburgh, EH9 355 (Gt. Britain) (Received 6 March 1990) ABSTRACT The molecular structure of 1,2,3-trichlorobenzene (A) has been determined by using data from gas electron diffraction experiments and direct dipolar couplings from ‘H NMR experiments in a joint structural analysis. The data are consistent with an assumed molecular model of C, sym- metry and all 11 structural parameters could be refined simultaneously, with standard deviations between 0.3 and 0.7 pm for bond lengths and less than 0.44” for valence angles. The crystal and molecular structures of A have also separately been determined by X-ray crystallography. The mean structural parameters in the solid state are almost equal to those obtained from the joint analysis. INTRODUCTION zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA The three different isomers of trichlorobenzene shown, A, B and C, have very similar physical properties. However, as structural problems they are quite different. 1,2,3-Trichlorobenzene (A) as a free molecule is expected to be of CZV sym- metry, and requires 11 independent structural parameters for a complete de- C *On leave from Department of Chemistry, University of Oslo. 0022-2860/90/$03.50 0 1990 - Elsevier Science Publishers B.V.