Reaction of Cyclooctenes with Singlet Oxygen. Trapping of a Perepoxide Intermediate
Reaction of Cyclooctenes with Singlet Oxygen. Trapping of a Perepoxide Intermediate
复制标题
环辛烯与单线态氧的反应。
DOI：
10.1021/ja00134a005
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发表时间：
1995
影响因子：
15
通讯作者：
C. Foote
中科院分区：
文献类型：
--
作者：
Thomas H. W. Poon;Kenneth Pringle;C. Foote
在两种不同极性的溶剂中测定了顺式和反式环辛烯对单线态氧 (2) 的总物理和化学猝灭 (kq+ kr) 的产物和速率常数。 Small amounts of ciscyclooctene are produced during the reaction of the trans-isomer.在CDCI 3 和丙酮-de中，反式环辛烯的kq+k为1.3 x 104 M-1 s-1，而反式环辛烯的反应速率常数(kr)分别为2.3 x 104和3.4 x 104 M-1 s-1。 2-甲基-2-戊烯 (2M2P) 的竞争实验表明，反式烯烃的物理猝灭贡献很大，而反式烯烃主要通过化学反应去除 2。反式环辛烯对 2 的物理猝灭是通过过环氧化物中间体来解释的，该过环氧化物中间体可以打开两性离子，该两性离子可以提取烯丙基氢以得到 3-氢过氧环辛烯产物或异构化并失去 O2 以形成顺式环辛烯。 A perepoxide intermediate can be trapped using triphenyl phosphite with transbat not cis-cyclooctene. frans-Cyclooctene quenches 3C7o with a rate constant of 3.4 x 105 M-1 s-1.
The products and rate constants for total physical and chemical quenching (kq+ kr) of singlet oxygen (2) by cis-and frans-cyclooctene were determined in two solvents of different polarity. Small amounts of ciscyclooctene are produced during the reaction of the trans-isomer. In CDCI3 andacetone-de, kq+ k, for ris-cyclooctene was 1.3 x 104 M-1 s-1 while the rate constants (kr) for the reaction of trans-cyclooctene were 2.3 x 104 and 3.4 x 104 M-1 s-1, respectively. Competition experiments with 2-methyl-2-pentene (2M2P) suggest a substantial contribution of physical quenching for the frans-alkene while the ris-alkene removes 2 mostly by chemical reaction. The physical quenching of 2 by frans-cyclooctene is explained by a perepoxide intermediate which can open to a zwitterion that can abstract an allylic hydrogen to give the 3-hydroperoxycyclooctene ene product or isomerize and lose O2 to form cw-cyclooctene. A perepoxide intermediate can be trapped using triphenyl phosphite with transbat not cis-cyclooctene. frans-Cyclooctene quenches 3C7o with a rate constant of 3.4 x 105 M-1 s-1.