Carbocation-like reactivity patterns in X'-substituted-4-biphenylylnitrenium ions
作者:Daniel Ren、Robert A McClelland
DOI:10.1139/v97-204
日期:1998.1.1
ion, with values of kaz ranging from 6 to 10 x 109 M-1 s-1, with the majority in the range (9-10) x 109. This near constant kaz provides further evidence that arylnitrenium ions are quenched by azide ion at the diffusion limit. The solvent reactivities, plotted in a single-parameter Hammett plot against σ sup + (X), exhibit a poor correlation, with the points for the para π-electron donors deviating
4-叠氮基-X'-取代的联苯 (X' = 4'-MeO, 4'-Me, 4'-F, 3'-Me, 4'-Cl, H, 3'-MeO, 3'-Cl, 4'-CF3) 已制备并在 20:80 乙腈:水中进行 248 nm 闪光光解照射。观察到瞬态 X'-取代的 4-联苯基硝基离子 10 (Ar C6H4-N + H),寿命范围从 0.6 ms (4'-MeO) 到 26 ns (4'-CF3)。这些阳离子被叠氮离子淬灭,kaz 的值范围从 6 到 10 x 109 M-1 s-1,大部分在 (9-10) x 109 的范围内。这个接近恒定的 kaz 进一步证明了芳基氮离子在扩散极限被叠氮离子淬灭。在单参数哈米特图中绘制的溶剂反应性与 σ sup + (X) 的相关性较差,对 π 电子供体的点偏离基于其他取代基的相关线,朝着需要更负的取代基参数的方向发展。数据更符合二参数 Yukawa-Tsuno