PHOTOINDUCED ELECTRON-TRANSFER REACTIONS OF ARYL GLYCOSIDES

Article abstract of DOI:10.1016/0008-6215(83)88075-6

The photolytic effects of ultraviolet, as well as other electromagnetic, radiation on carbohydrates are of interest in connection with photodegradation of cellulose and potential application in the photolytic cleavage of lignocellulosic bonds.Aryl glycosides, model compounds for lignocellulosic systems, were irradiated under conditions selected to achieve photoinduced electron-transfer.Various anomeric phenyl D-gluco- and D-galacto-pyranoside solutions in acetonitrile satureted with oxygen, air, or nitrogen and containing 1,4-dicyanonaphtalene (DCN) were irradiated at 350 nm for extended periods, and cleavage of the radical cation formed upon electron transfer to give the simple monosaccharide and phenol was observed.In the presence of methanol, it is possible to intercept the cationic intermediate, with formation of the corresponding methyl glycosides.Control experiments conducted in the presence of oxygen, air, or nitrogen in the absence of DCN showed little or no conversion.Comparison of the modes of fragmentation in solution with those observed in the gas phase upon electron impact in the mass spectrometer was made, and mechanisms for the reactions induced by electron transfer under these conditions are proposed.