Deb Sanghamitra, Weber Peter M
Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA.
Annu Rev Phys Chem. 2011;62:19-39. doi: 10.1146/annurev.physchem.012809.103350.
The photochemically induced electrocyclic ring-opening reaction of 1,3-cyclohexadiene to 1,3,5-hexatriene serves as a prototype for many important reactions in chemistry and in biological systems. Based on experimental and computational studies, a detailed picture of the reaction has now emerged: Excitation to the Franck-Condon region places the molecule on a steeply repulsive part of the 1B potential energy surface, which propels the molecule in exactly the conrotatory direction that conforms to the Woodward-Hoffmann rules of orbital symmetry. Bypassing a cusp in a symmetry-breaking direction, the wave packet enters the 2A state within 55 fs. It continues to move directly toward the 2A/1A conical intersection, where it crosses in approximately 80 fs to the ground state. This article summarizes the published experimental and theoretical work to describe the current understanding of the reaction while pointing to important questions that remain to be addressed.
1,3-环己二烯光化学诱导的电环化开环反应生成1,3,5-己三烯，是化学和生物系统中许多重要反应的一个原型。基于实验和计算研究，该反应的详细情况现已明晰：激发到弗兰克-康登区域会使分子处于1B势能面的一个陡峭排斥部分，这会促使分子沿完全符合轨道对称性伍德沃德-霍夫曼规则的对旋方向运动。波包在一个对称破缺方向绕过一个尖点，在55飞秒内进入2A态。它继续直接朝着2A/1A锥形交叉点移动，在那里大约80飞秒后穿越到基态。本文总结了已发表的实验和理论工作，以描述目前对该反应的理解，同时指出仍有待解决的重要问题。
