The Cyclohexadienyl Radical in the Thermal Syn−Anti Isomerization of Two Crossed Pentaenes of the Type of Bis-Homofulvalene
作者:W. von E. Doering、Ludmila Birladeanu、Keshab Sarma、Li-Sming Shao
DOI:10.1021/ja953416z
日期:1996.1.1
elucidation of the dependence of enthalpy of stabilization on configuration among the pentadienyl radicals, a designer pentaene of the (Z,Z) type, (R,R)-5,5‘,6,6‘,7,7‘,8,8‘-octahydro-4a,4a‘-dimethyl-2,2‘-bi-4a(H)-naphthylidene, has been prepared and subjected to a kinetic study of cis, trans isomerization about its central double bond. The resulting activation parameters and those of a more complicated
为了进一步阐明稳定焓对戊二烯基自由基构型的依赖性,设计了 (Z,Z) 型 (R,R)-5,5',6,6',7,7' 的戊烯,8,8'-octahydro-4a,4a'-二甲基-2,2'-bi-4a(H)-naphthylidene,已制备并对其中心双键进行顺反异构化的动力学研究。所得的活化参数和更复杂的例子 3,3'-bicholesta-1,4-二亚苯基的活化参数基本相同,它们的平均值为 ΔH⧧ = 36.8 kcal/mol 和 ΔS⧧ = +1.8 eu。这种活化焓显着高于 (E,E) 和 (E,Z) 构型的戊烯。双高富瓦烯型共面交叉共轭体系中的共轭相互作用尚未通过理论计算进行实验评估或估计,环己二烯基的稳定焓目前还不能确定。如果将共轭相互作用等同于四个 Kistiako ......