USE OF C-13 SATELLITES IN PROTON SPECTRA OF ORIENTED MOLECULES - THE R-ALPHA-STRUCTURE OF 1,2,3-TRICHLOROBENZENE

It is demonstrated that proton spectra of oriented molecules which do not carry any structural information can still be used to determine the entire molecular structure if the 13C satellites are also considered. As an example the spectrum of 1,2,3-trichlorobenzene is analyzed and the rα structure is obtained. CH and CC bond lengths as well as bond angles are derived and compared with benzene and monochlorobenzene. The chlorine substituents are found to induce bond length changes of less than 1% and bond angle variations smaller than 2°. Certain regularities in the deformations, as e.g., a general elongation of bonds which are parallel to the molecular electric dipole axis, are detected. The spectrum of 1,2,3-trichlorobenzene is also analyzed in an isotropic solvent for determining the indirect coupling constants. In this analysis one-bond carbon-13 isotope effects on the proton chemical shifts are measured. © 1979.