Photochemical reactions of coumalic acid (12) and its methyl, isopropyl, and benzyl esters have been investigated in solution and in the solid phase. In solution the photochemistry has been carried out in hydroxylic and nonhy- droxylic solvents as well as in ethyl bromide. In the solid phase, the reaction has been studied in a potassium bro- mide matrix and as a sandwich between quartz plates. A particularly interesting effect of KBr, suggested to be a heavy atom effect ...
