Steric effect on photochemistry of benzyl ester derivatives 2.: Effects of substituents and oxygen on photolysis of α-methyl-substituted benzyl alkanoates

被引:5
作者
Goshima, T
Itoh, Y [1 ]
Kojima, M
Karatsu, T
机构
[1] Shinshu Univ, Fac Text Sci & Technol, Ueda, Nagano 3868567, Japan
[2] Shinshu Univ, Fac Agr, Matsumoto, Nagano 3908621, Japan
[3] Chiba Univ, Fac Engn, Chiba 2638522, Japan
关键词
photolysis; benzyl ester; substituent effect; steric hindrance;
D O I
10.1016/S1010-6030(99)00136-7
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The photochemistry of alpha-methyl-substituted benzyl acetates and pivalates, la-e and 2a-c, respectively, has been examined in methanol (MeOH). Sensitization and quenching experiments confirmed the predominance of the singlet-state photolysis of these esters. The product distribution depended on methyl groups, on the methylene carbon, and/or alkyl groups attached to the carbonyl group. Ester conversion decreased with methyl substitution. These results are explicable on the basis of steric hindrance, or conformational restriction, around the ester bond. We also found that the photolysis was markedly affected by oxygen, particularly for the most hindered ester 2c. It is likely that the effect of oxygen is attributed to the formation of an excited charge-transfer complex between the esters and an oxygen molecule. (C)1999 Elsevier Science S.A. All rights reserved.
引用
收藏
页码:75 / 81
页数:7
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