Mercury-Photosensitized Decomposition of β-Butyrolactone

Abstract

Abstract The mercury-photosensitized decomposition of β-butyrolactone has been investigated at temperatures between 353 and 393 K and pressures from 450 to 13600 Pa. The products were carbon dioxide, propylene, carbon monoxide, propylene oxide, acetone, and acetaldehyde. The yields of these products increased linearly with reaction time and light internsity, while they were independent of the lactone pressure. Three decomposition processes were proposed to explain the formation of the products. The decrease in the quantum yields of carbon dioxide, carbon monoxide, and acetaldehyde observed in the presence of cis-2-butene can be explained by the competitive quenching of the triplet mercury atom by the lactone and cis-2-butene (the quenching efficiency of lactone relative to that of cis-2-butene was estimated to be 0.61). The decrease in the quantum yields of carbon dioxide, propylene, and acetaldehyde by the addition of oxygen can again be explained only by the competitive quenching of the triplet mercury atoms by lactone and oxygen (kQ(lactone)/kQ(oxygen)=1.36). The quantum yields of propylene oxide and acetone, however, decrease more rapidly than predicted for competitive quenching. This indicates the existence of a reaction between oxygen and a biradical, which is a precursor of propylene oxide and acetone.