A THEORETICAL INVESTIGATION OF THE THERMAL RING-OPENING OF CYCLOPROPYL RADICAL INTO ALLYL RADICAL - EVIDENCE FOR A HIGHLY NONSYMMETRIC TRANSITION-STATE

被引:62
作者
OLIVELLA, S [1 ]
SOLE, A [1 ]
BOFILL, JM [1 ]
机构
[1] UNIV BARCELONA,DEPT QUIM FIS,E-08028 BARCELONA,SPAIN
关键词
D O I
10.1021/ja00162a017
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
An ab initio investigation of the thermal ring opening of cyclopropyl radical (1) to give allyl radical (2), with geometries optimized at the UHF/3-21G and CASSCF/3-21G levels of theory, predicts a highly nonsymmetric structure for the transition state of such an electrocyclic reaction. Thus, the CASSCF/3-21 G-optimized transition structure corresponds to rotation of one of the methylene groups in 1 through 24° while the other remains orthogonal to the plane of the carbon atoms, the length of the CC bond undergoing rupture being 2.066 Å. The present results agree with those of early MINDO/3 calculations by Dewar and Kirschner in the important respect that the minimum-energy reaction path does not involve synchronous rotation of the methylene groups, so that one methylene rotation is almost completed before the other commences. As a consequence, both conrotatory and disrotatory ring-opening modes of 1 involve a common transition state. © 1990, American Chemical Society. All rights reserved.
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页码:2160 / 2167
页数:8
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