THE STRUCTURE OF 1,6,6Aλ4-TRITHIAPENTALENE AND OXYGEN ANALOGUES STUDIED BY MEANS OF NMR SPECTROSCOPY IN AN ISOTROPIC AND AN ANISOTROPIC PHASE

Abstract The NMR spectra of 1 and 2 have been recorded in both an isotropic (CDCl3) phase and an anisotropic phase (N-(4′-ethoxybenxylidene)-4-butylaniline (EBBA) and 3 in an isotropic phase. The structure of the compounds may be described by the following formulae, where 4 - 6 can be resonance forms of the same molecule or be different valence tautomers. If structure 4 is correct the compounds should be found to possess C2v symmetry for X = Y, whereas 5 and 6 have only Cs symmetry. For 1 and 2 data from both isotropic and anisotropic experiments are in accordance with C2v symmetry, this is for 2 supported by a microwave study (ref. 1). From the dipole-dipole coupling constants obtained from the spectra in EBBA it has been possible to evaluate relative structural parameters for the two compounds 1 and 2, which seem to have a slightly different geometry. The data from an isotropic phase for 3 are in agreement with a structure which is in between 5 and 6.