Yields of excited states from thermolysis of some 1,2-dioxetanesl

The singlet 1Φ and triplet 3Φ excited state product yields produced on thermolysis in toluene of trimethyl- (1), tetramethyl- (2), cis-3, 4-butano-3,4-dimethyl- (3), and 3,4:3,4-dibutano-1,2-dioxetane (4) were determined to be as follows (dioxetane, °C, 1Φ, 3Φ): 1, 40, 1.1 × 10−3, 0.15; 2, 45, 4.4 × 10−4, 0.31; 3, 26, 8.5 × 10−4, 0.23; 4, 24, 4.8 × 10−6, 0.011. The reason for the low yield of excited states obtained from 4 is not known. Thermochemical calculation indicate that as much energy is available from thermolysis of 4 as is available from 2.Dioxetane-energized dimerization of acenaphthylene, accompanied by an intense yellow luminescence, produced mainly the trans dimer in 1–3% yield. Dioxetane-energized cyclization of 1-(2,4-dimethylphenyl)-1,2-propanedione produced 2-hydroxy-2,5-dimethylindan-1-one in 0.5–6% yields.