27770-45-2Relevant academic research and scientific papers
Carbonyl Ylides Photogenerated from Isomeric Stilbene Oxides. Temperature Dependence of Decay Kinetics
Kumar, C. V.,Chattopadhyay, S. K.,Das, P. K.
, p. 5639 - 5643 (1984)
Upon 266-nm laser excitation in fluid solutions, trans- and cis-stilbene oxides form isomeric carbonyl ylides (λmax's = 470 and 490 nm) that are spectrally and kinetically distinct from one another.Red shifted in absorption and considerably shorter-lived, the ylide photogenerated from the cis oxirane is assigned the cis-exo, exo structure on the basis of symmetry rules for electrocyclic ring opening; its counterpart from the trans oxirane is given the trans-exo, endo structure.The short lifetimes of the ylides arise in part from moderately small activation enthalpies (6-7 kcal mol-1) and in part from small and negative activation entropies (-5 to -7 eu).Laser flash photolysis in acetonitrile gives rise to a second, longer-lived transient species (λmax = 335 nm) assignable as the nitrile ylide derived from phenylcarbene and an acetonitrile molecule.Bimolecular rate constants in the range 106 - 109 M-1s-1 are presented for the reactions of carbonyl and nitrile ylides with several dipolarophiles.
