Structural and solvent effects in the photochemistry of aliphatic ketones

Abstract

Structural and solvent effects have been investigated by determining triplet yields, triplet lifetimes and fluorescence decay times with the sensitized T-T absorption and time-resolved fluorescence techniques. Methyl ethyl ketone, methyl isopropyl ketone and methyl tert-butyl ketone were were studied in iso-octane, alcohols and acetonitrile. The triplet lifetimes and quantum yields for triplet state formation were found to decrease significantly with increasing substitution in the α position. The triplet yields as well as the fluorescence decay times also changed with the nature (polarity and hydrogen-donating ability) of the solvent and with ketone concentration. The results were explained by assuming that singlet and triplet excimers contributed to the primary photophysical processes.