Oxygen and sulphur heterocycles derived from chloroaldehydes

Doctoral Thesis


Permanent link to this Item
Journal Title
Link to Journal
Journal ISSN
Volume Title

University of Cape Town

Chloral may be trimerised, tetramised and polymerised, to form parachloral, metachloral and polychloral, respectively. Parachloral has two isomers: the cis-isomer and the trans-isomer. An analysis of the conformational equilibria occuring in solution, was carried out for trans-parachloral, using the techniques of dipole moment measurement and infrared and nmr spectroscopy Both isomers exist in cis-chair conformations, but differ in the chirality of the β-carbon atoms in the side chains. A comparison of the mass spectral fragmentations of parachloral and parabutylchloral is included. The structure of a related five-membered heterocycle, trans-chloralide was also investigated by x-ray crystallography. The cis-isomer of chloralide is reported for the first time. The unusual mechanism, in which carbon monoxide acts as nucleophile, by which chloralide is formed from chloral and fuming sulphuric acid, has been elucidated using 13C-labelling. The dehydrochlorination of chloralide under unexpected conditions, is also discussed. The isomerism in a series sulphur-containing analogues of parachloral was investigated. 2-Trans-dithioparachloral and its dehydrochlorination product, were shown by x-ray crystallography. A comparative study of the effects on the 1H and 13Cnmr spectra, of structural changes in these six-membered heterocycles, is discussed at length. Some introductory preparative work was done, regarding the potential use of 1,3,5-trithiane 1,3,5-trioxides with three axial sulphoxide groups, as terdentate ligands.

Includes bibliography.