Radical scavenging and excited state quenching efficiency of additives in the photochemistry of acetone

The effect of hydrogen sulphide, ethanethiol, diethyl sulphide and diethylhydroxylamine on the gas phase photolysis of acetone has been studied. Diethylhydroxylamine was found to be much more reactive than thiols and thioethers towards the nπ^* triplet state of acetone. However, H₂S and C₂H₅SH proved to be more effective methyl-radical trapping agents than diethylhydroxylamine. The following kinetic data were determined for hydrogen-atom abstractions by CH₃ from C₂H₅SH and (C₂H₅)₂NOH respectively:

These data were used to characterize the radical scavenging efficiencies of the thiol and hydroxylamine compounds, while quenching data indicated the triplet quenching efficiencies of the substrates studied.