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Chemical & pharmaceutical bulletin

Studies on photochemical reactions of air pollutants. XV. Photoreactivity of heptachloro-3'-cyclopentenyldioxy heptachloro-2-cyclopentene formed by exposure of hexachlorocyclopentadiene to ultraviolet light in air.


PMID 16508188

Abstract

Hexachlorocyclopentadiene (HCCP, 1), one of the starting materials in the synthesis of aldrin (3), was found to be able to epoxidize aldrin (3) to give dieldrin (4) when exposed to artificial light at wavelengths longer than 290 nm. In this photochemical reaction, heptachloro-3'-cyclopentenyldioxy heptachloro-2-cyclopentene (2) was isolated as a key intermediate, which appears to be derived from the interaction between the triplet state of photo-excited HCCP (1) and triplet oxygen (3sigma(g)-), but not from that between the ground state of HCCP (1) and singlet oxygen (1delta(g)). The peroxide (2) plays an important role in the formation of dieldrin (4), because it utilized oxygen atom derived from oxygen in air for the epoxidation.