B.Sc., 1955, University of Malaya; M.Sc., 1957, University of Malaya; Ph.D., 1959, Oxford University; D.Sc., 1972, University of Singapore
Department of Chemistry, NUS
3 Science Drive 3
My research interests lie in two general areas (i) conformational analysis of derivatives of the ethane molecule and (ii) the study of the thermal decomposition of heterocyclic molecules by means of UV photoelectron spectroscopy. In the area of the of the derivatives of ethane my interest has centred on nitro and cyano-substituted ethane derivatives of the type (R'R"XC)-(CR'R"X) where X=nitro or cyano. The conformational analysis consists of measuring the dipole moments and Kerr constants of the compounds concerned in solution , as well as their infrared and Raman spectra in the solid state and solution. We have also determined the X-ray crystal structures of the compounds where appropriate. In the interpretation of our results we have also made comparisons with theoretical predictions based on semi-empirical MO calculations using AM1 and PM3 methods in terms of gauche/trans isomeric ratios, the dihedral angle of the gauche form and the energy separating the gauche and trans isomers.
In the area of UV photoelectron spectroscopy we have measured the spectra of some new and not so new compounds with a view to interpreting their electronic structure. These molecules include some nitro compounds. The thermal decomposition of some heterocyclic molecules have been studied. UV photoelectron spectroscopy offers among the analytical methods suitable for the study of gaseous reactions, the advantages of small sample size, ready identification of products with characteristic bands and detection of semi-stable species. Some of the molecules whose decomposition pathways have been studied include thiirane and 2-methylthiirane, gamma-butyrolactone and gamma-thiobutyrolactone, methylated gamma-thiobutyrolactones and 2-pyrrolidinone and 2-pyrrolidinethione. Current studies include the thermal decomposition of oxetan-2-one, 4-methyl-oxetan-2-one and azetidinone; 2-butene-1-thiol and 2-methyl-2-propene-1-thiol; 2-buten-1-ol, 2-methyl-2-propen-1-ol and 3-buten-2-ol; 2(3H)-furanone, 2(5H)-furanone and 4-methyl-2(5H)-furanone; tetronic and thiotetronic acids; gamma-thiobutyrolactone, gamma-thiovalerolactone and 3-methyl-gamma-thiobutyrolactone; and 2-imidazolidinethione, 2-oxazolidone and 2-thiazolidone. To aid in the interpretatiion of the decomposition mechanisms semi-empirical MO calculations have also been used.
Expanded spectrum at 1040oC during pyrolysis of gamma-thiovalerolactone: (a) ethanethiol; (b) thioacetaldehyde; (c)butadiene; d) thioformaldehyde