THERMAL-DECOMPOSITION OF METHYLATED GAMMA-THIOBUTYROLACTONES - A PHOTOELECTRON SPECTROSCOPIC STUDY

The thermal decomposition of gamma-thiovalerolactone, alpha-methyl-gam ma-thiobutyrolactone and beta-methyl-gamma-thiobutyrolactone has been studied in a gaseous flow system, by monitoring the changes in the pho toelectron spectra recorded during the course of the reactions. Three modes of decomposition were observed, two involve loss of carbon monox ide (decarbonylation) and one involves loss of carbonyl sulfide (decar boxylation). The decarbonylation reaction producing an olefin and a th ioaldehyde and the decarboxylation producing an olefin are similar to those observed for the unsubstituted thiobutyrolactone. The third reac tion, observed only in the methylated compounds, is decarbonylation wi th the formation of hydrogen sulfide and butadiene. It is proposed tha t the last reaction can be attributed to the relatively facile elimina tion reaction of a butenethiol intermediate.