Photodissociation of chalcogenides: laser flash photolysis and product analysis study

J. E. ARGÜELLO,ANDREA BARRIONUEVO,LYDIA BOUCHET, LUCIANA SCHMIDT, ALICIA PEÑEÑORY

La Serena Chile

Congreso; X ELAFOT 2010; 2010

ELAFOT

The photochemistry of thioetheres has been somewhat sparsely studied over the years, in general aliphatic thioeters undergo homolytic dissociation, both in solution and in the gas phase, with aryl thioeters, photohomolysis may be followed by in cage electron transfer to give an ion pair.Selenides and tellurides have been used as a source of ketones by irradiation in the presence of molecular oxygen. However, systematic investigation or basic data such as quantum yields measurement and kinetic information are scarce at present. As a contribution to the understanding of the photochemistry of the C-S or C-Se moiety, we present report the irradiation of a series of aryl diphenylmethyl sulfides and selenides, ArSCHPh2 and ArSeCHPh2, for the former electron donating and electron withdrawing groups were included in the aromatic ring, for the selenides phenyl, anisyl and naphthyl derivatives were studied.The involvement of the intermediates Ph2CH•, ArS• and ArSe• were identified using laser flash photolysis (266 nm, figure 1). Product analysis (254 nm) gives as a main product 1,1,2,2-tetraphenylethane with the formation of a new carbon-carbon bond  and diaryldichacogenides as a main products all these compounds are formed from the radicals through coumpling, in a minor extent H-abstraction products were also found (ec. 1).