DFT Evidence for a Stepwise Mechanism in the <i>O</i>-Neophyl Rearrangement of 1,1-Diarylalkoxyl Radicals
作者:Massimo Bietti、Gianfranco Ercolani、Michela Salamone
DOI:10.1021/jo070125n
日期:2007.6.1
b. The first-order rearrangement rate constants [kobs = k1k2/(k-1 + k2)] were thus obtained from the computed activation free-energies and were compared with the experimental rate constants measured previously in MeCN solution by laser flash photolysis. An excellent agreement is observed along the two series, which strongly supports the hypothesis that the O-neophyl rearrangement of 1,1-diarylalkoxyl
在理论上的UB3LYP / 6-31G(d)水平上已经进行了相对于一系列环取代的1,1-二芳基烷氧基自由基的O-新叶重新排列的势能面(PES)的混合DFT计算。上的计算数据的基础上,重新布置可被描述为所述类型的连续反应一⇆ b → c ^(见上文的图形),和稳态近似可以在所有情况下的中间应用b。一阶重排速率常数[ k obs = k 1 k 2 /(k - 1 + k 2)]因此从计算出的活化自由能中获得,并与先前通过激光闪光光解法在MeCN溶液中测得的实验速率常数进行比较。沿两个系列观察到了极好的一致性,这强烈支持了以下假设:1,1-二芳基烷氧基的O-新叶酸重排通过反应性1-oxaspiro [2,5]辛二烯基自由基中间体的形成而进行。这与先前的假设相反,后者涉及长寿命的中间体或沿反应路径缺少该中间体。从甲氧基取代的基团(ΔG °= -16.4 kcal·mol - 1)变为硝基取代的基团(ΔG