作者:Peter J. Wagner、Michael J. Thomas、Allen E. Puchalski
DOI:10.1021/ja00284a042
日期:1986.11
The photoreactivities of the mono-, di-, and tri-..cap alpha..-fluorinated acetophenones have been compared to that of acetophenone itself. All four ketones have similar triplet excitation energies; the three fluorinated ketones have reduction potentials 0.5-0.7 eV lower than that of acetophenone. Triplet reactivity toward alkylbenzenes keeps increasing with fluorine substitution, since the rate-determining
单-、二-和三-..帽α..-氟化苯乙酮的光反应性已与苯乙酮本身的光反应性进行了比较。所有四种酮都具有相似的三线态激发能;三种氟化酮的还原电位比苯乙酮低0.5-0.7 eV。随着氟取代,对烷基苯的三重反应性不断增加,因为随着酮还原电位的降低,速率决定步骤变为电荷转移络合。一级/三级 CH 对对伞花烃的选择性随着氟的数量增加而增加。对环戊烷的三线态反应性也因氟化而增加,但在两个氟原子处达到峰值,因为最低的三线态从 n,..pi..* 转换为 ..pi..,..pi..* 与两个或三个氟原子和..皮..,..皮.. * 三元组在简单的氢原子提取中是无反应的。相反,戊苯酮的..cap alpha..-氟化不会显着增加三重..gamma..-氢提取的速率。对反应性的诱导效应显然被构象效应所抵消。..cap α..-氟化苯酮主要产生环丁醇而不是 Norrish II 型消除。..cap alpha.