REACTIVITY OF LOW ENERGY EXCITED STATES. MECHANISTIC AND EXPLORATORY ORGANIC PHOTOCHEMISTRY

Article abstract of DOI:10.1016/S0040-4020(01)92371-3

The photochemistry of 3-methyl-3-(1'-naphthyl)-1-butene was investigated.Direct irradiation led to 1,1-dimethyl-2-(1'-naphthyl)cyclopropane as a primary photoproduct and 2-methyl-4-(1'-naphthyl)-1-butene as a secondary product.The quantum yield for the formation of the cyclopropane was 0.037.The corresponding triplet reaction was less efficient, with a quantum yield of 0.012, but still afforded the same product.The excited singlet rearrangement rate was determined by single photon counting; this proved to be ¹k_r = 5.9 x 10⁵ sec^-1.The total rate of S₁ decay was determined as 1.59 x 10⁷ sec^-1 with a lifetime of 62.9 nsec.Thus, the lifetime of this rearranging system is quite similar to that of simple 1-alkylnaphthalenes (ca 65 nsec); and, the rate of di-?-methane rearrangement is the slowest known.Finally, the rate of radiationless decay of the singlet was found to be almost temperature independent between room temperature and 77 K.