EXPERIMENTAL AND THEORETICAL-STUDY OF PHOTOENOLIZATION MECHANISM FOR 1-METHYLANTHRAQUINONE

被引:40
作者
GRITSAN, NP
KHMELINSKI, IV
USOV, OM
机构
[1] Institute of Chemical Kinetics and Combustion, 630090 Novosibirsk, USSR
关键词
D O I
10.1021/ja00025a029
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Photoenolization of 1-methylanthraquinone (AQ) and its deuterated analogue (AQ-d6) has been studied by laser flash photolysis over a wide temperature range (120-340 K). Phototransfer of a H (or D) atom has been found to occur in both the singlet and triplet n-pi* states. The temperature dependence of the efficiency of the phototransfer of H and D atoms in the 1n-pi* state has been analyzed. Piperylene quenching of AQ and AQ-d6 triplet excited states has been studied. The rate constants of H- and D-atom phototransfer at room temperature have been estimated to be ca. 3 X 10(10) s-1 and ca. 10(10) s-1, respectively. Quantum-chemical calculations of potential energy surfaces and of electronic and geometrical structures of key intermediates have been performed by using the AM1 technique. A triplet sigma,pi-biradical has been found to be the intermediate preceding the formation of 9-hydroxy-1,10-anthraquinone-1-methide (AQM). It has been revealed that thermal transformation of the enol AQM to the initial quinone AQ can occur as an intramolecular process via reverse transfer of a H atom, or as a second-order reaction. The latter appears to involve the transfer of two H (or D) atoms in a collisional complex of two AQM molecules. The dependence of the rate constants of the intramolecular thermal transfer of H and D atoms on temperature and solvent nature has been analyzed.
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页码:9615 / 9620
页数:6
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