%0 Journal Article
%T Laser flash photolysis study of the phenolic hydrogen abstraction by 1,2-aceanthrylenedione triplet
%A Serra
%A Ana Cristina S.
%A Lucas
%A Nanci C. de
%A Netto-Ferreira
%A Jos¨¦ Carlos
%J Journal of the Brazilian Chemical Society
%D 2004
%I Sociedade Brasileira de Qu¨ªmica, SBQ
%R 10.1590/S0103-50532004000400006
%X the nanosecond laser flash photolysis technique has been used to study the reactivity of 1,2-aceanthrylenedione (1) triplet towards phenols. using acetonitrile as solvent, the quenching rate constant kq ranged from 3.3 x 105 l mol-1s-1 (phenol) to 1.3 x 107 l mol-1s-1 (4hydroxyphenol). phenols with electron donating substituents were more reactive. the kinetic isotope effect (kh/kd) observed for the quenching of 1 with 4-methoxyphenol was 1.5. the hammett plot for the reaction of the triplet of 1 with phenols gave a reaction constant r = 1.04 in acetonitrile solution. the low value for the quenching rate constant measured for this triplet with 1,3-cyclohexadiene (kq=2.0 x 104 l mol-1s-1) and the diffusion controlled quenching rate constant obtained for b-carotene suggest that the energy of the lowest triplet state for 1,2-aceanthrylenedione is located between 88 and 219 kj mol-1.
%K laser flash photolysis
%K diketones
%K hydrogen abstraction
%K triplet state.
%U http://www.scielo.br/scielo.php?script=sci_abstract&pid=S0103-50532004000400006&lng=en&nrm=iso&tlng=en