Delocalization resonance energy of the allylic radical from the geometrical isomerization of hexa-1,3,5-trienes
作者:W. von E. Doering、G.H. Beasley
DOI:10.1016/s0040-4020(01)93343-5
日期:1973.1
These geometrical isomers undergo uncomplicated thermal cis, trans isomerization in vessels of lead-potash glass: log k1 = 12·03±0·32−41·7±0·8/(0·004575Tabs). Extraction of a value for allylic delocalization energy from the behavior of hexa-1, trans-3,5-triene [log k1 = 12·91 ± 0·47−44·3±1·2/(0·004575 Tabs)] requires corrections of the Dewar-Schmeising type for changes in hybridization of the σ bonds.
热顺,反几何异构化理论上涉及90°扭曲的单重双自由基状过渡态,可作为检查结构扰动的基础。尽管由于随后的环化反应和1,5氢转移,活化作用,无法直接追踪hexa-1,反式-3,5-三烯(和全反式八,2,4,6-三烯)向顺式异构体的热重排确定了消失的参数。在双环己三烯,环戊烯基亚烷基环戊烯中消除了难以解释的实验复杂性和机理不确定性。这些几何异构体经历简单的热顺,反铅钾玻璃容器中的异构化:log k 1 = 12·03±0·32-41·7±0·8 /(0·004575T abs)。从hexa-1,trans -3,5- triene的行为中提取烯丙基离域能的值[log k 1 = 12·91±0·47-44·3±1·2 /(0·004575 T abs)]需要对杜瓦-施密斯(Dewar-Schmeising)类型进行校正,以改变σ键的杂交情况。根据以乙烯还是反丁烯为标准,得出的值分别为12·2和13·1