Laser flash photolysis study of the phenolic hydrogen abstraction by 1,2-aceanthrylenedione triplet

Journal of the Brazilian Chemical Society

Ana Cristina S. Serra²  Nanci C. De Lucas²  José Carlos Netto-ferreira¹ 

[1] ,Universidade Federal do Rio de Janeiro Instituto de Química Rio de Janeiro RJ ,Brazil

关键词: laser flash photolysis;    diketones;    hydrogen abstraction;    triplet state;   

DOI  :  10.1590/S0103-50532004000400006

来源: SciELO

【 摘 要 】

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 k q ranged from 3.3 x 10(5) L mol-1s-1 (phenol) to 1.3 x 10(7) 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 rho = 1.04 in acetonitrile solution. The low value for the quenching rate constant measured for this triplet with 1,3-cyclohexadiene (k q=2.0 x 10(4) L mol-1s-1) and the diffusion controlled quenching rate constant obtained for beta-carotene suggest that the energy of the lowest triplet state for 1,2-aceanthrylenedione is located between 88 and 219 kJ mol-1.

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