54560-44-0Relevant articles and documents
Phenolic hydrogen abstraction by the triplet excited state of thiochromanone: A laser flash photolysis study
Ribeiro, Alessandra M.,Bertoti, Ada Ruth,Netto-Ferreira, Jose? Carlos
scheme or table, p. 1071 - 1076 (2010/10/21)
Triplet ketones are known to oxidize biological substrates which can lead to damage of several biomolecules such as amino acids, nucleosides and DNA. As part of our systematic study on the interaction between carbonyl compounds and phenols, the triplet reactivity of thiochromanone (1) towards substituted phenols, in acetonitrile, was investigated employing the laser fash photolysis technique. The quenching rate constants ranged from (1.1 ± 0.1) × 108 L mol-1 s-1 (4-cyanophenol) to (5.8 ± 1.0) × 109 L mol-1 s-1 (hydroquinone). A Hammett plot for the reaction of triplet 1 with phenols containing polar substituents resulted in a reaction constant ρ =-0.90. This negative value observed for the reaction constant ρ is in accord with a mechanism in which the hydrogen transfer from phenols to the triplet carbonyl involves a coupled electron/proton transfer.
Effect of Ring Substitution on the Photochemistry of α-(Aryloxy)acetophenones
Netto-Ferreira, J.C.,Avellar, I.G.J.,Scaiano, J.C.
, p. 89 - 92 (2007/10/02)
The photochemistry of a series of 10 α-(aryloxy)acetophenones has been examined by quantum yield, product studies, and laser flash photolysis techniques.Triplet decay involves a competition of β-cleavage with intramolecular quenching by the β-aryl group, the latter being favored in all systems.Typical triplet lifetimes at room temperature range from 60 to 260 ps and are rather insensitive to the substitution pattern. β-Cleavage rate constants range between 1*107 and 3*109 s-1 and are strongly favored by electron releasing substituents, such as 4-methoxy.The determination of true quantum yields of β-cleavage requires the addition of thiophenol as a radical trap to prevent the efficient back reaction that takes place otherwise; under these conditions quantum yields range from 10-3 to 0.14, the highest value being obtained for the 4-methoxy and 4-hydroxy derivatives.
