Thermolysis and Chemiluminescence of Monocyclic 1,2,4-Trioxan-5-ones

Article abstract of DOI:10.1002/hlca.19940770716

The 3,6-substituted 1,2,4-trioxan-5-ones 11-14, on heating to 170-200 deg, underwent unimolecular thermolysis to generate electronically excited singlet ketones with an efficiency of ca. 0.2percent.The chemiluminescence quantum yields (Φ_CL) depended on the nature of the 6-substituents and increased linearly with temperature.The Arrhenius activation energies were obtained by measuring the rate of decay of luminescence and determined as 22.9, 30.4, 35.6, and 34.2 kcal/mol for 11-14, respectively.Step analysis of the chemiluminescence of 14 afforded an average activation energy of 44.3 kcal/mol.This latter result is explicable in terms of two decomposition paths, higher and lower in energy, leading to excited and 'dark' products, respectively.The thermolysis of trioxanones 12-14 lacking a H-atom at the 6-position is interpreted as involving successive rupture of the peroxide bond, excision of ketone at the 3-substituted end, and loss of CO2, to finally produce ketone originating from the 6-position (see Scheme 4).