1ST MEASUREMENTS OF ABSOLUTE RATE CONSTANTS FOR OXACARBENE INTERMEDIATES PRODUCED IN THE PHOTOCHEMISTRY OF BENZOCYCLOBUTENEDIONE

被引:47
作者
BOATE, DR
JOHNSTON, LJ
KWONG, PC
LEERUFF, E
SCAIANO, JC
机构
[1] NATL RES COUNCIL CANADA,DIV CHEM,100 SUSSEX DR,OTTAWA K1A 0R6,ONTARIO,CANADA
[2] YORK UNIV,DEPT CHEM,DOWNSVIEW M3J 1P3,ONTARIO,CANADA
关键词
D O I
10.1021/ja00180a030
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The photochemistry of benzocyclobutenedione in solution has been examined by use of laser flash photolysis techniques. Two rapid processes appear to compete. One leads to the formation of the long-lived bisketene IV, which can be readily observed (λmax 380 nm). The other process leads to oxacarbene III. This carbene could not be monitored directly, but probing techniques, with pyridine and adamantanethione as probes, lead to readily detectable ylides that can be employed to characterize the kinetic behavior of III. Thus, III lives about 20 μs in toluene and can be trapped by typical carbene scavengers such as alcohols. Carbene trapping by alcohols is in fact a complex reaction, since it also leads to equilibration with a short-lived intermediate (studied in detail in methanol/acetonitrile) that in turn can be trapped by alcohols, azides, and halides. This intermediate is tentatively assigned to carbocation VIII formed by solvent protonation of III. © 1990, American Chemical Society. All rights reserved.
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页码:8858 / 8863
页数:6
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