Photochemistry of sulphur compounds related to the 1,2-dithiole system. Part IV. Photoisomerization of α-[7-(5-aryl or -alkyl-1,2-dithiol-3-ylidene)]-4,5,6,7-tetrahydro-1,2-benzodithiol-3-ylidene ketones

Abstract

The photochemistry of a series of higher polysulphur analogues of 1,2-dithiol-3-ylidene ketones has been studied. The normal cis form is converted into the trans on irradiation of an ethanolic solution containing catalytic amounts of hydrogen chloride. The photoproduct reverts to starting material by a dark process, which obeys first-order kinetics. The rate constants are only slightly affected by variation of substituents.