Flash photolytic generation and study of<i>p</i>-quinone α-phenylmethide and<i>p</i>-quinone α,α-diphenylmethide in aqueous solution
作者:J. A. Chang、A. J. Kresge、H.-Q. Zhan、Y. Zhu
DOI:10.1002/poc.767
日期:2004.6
p-Quinone α-phenylmethide (7) and p-quinone α,α-diphenylmethide (8) were generated by flash photolytic dehydration of p-hydroxy-α-phenylbenzyl alcohol (9, R1 = Ph, R2 = H) and p-hydroxy-α,α-diphenylbenzyl alcohol (9, R1 = R2 = Ph) respectively, and rates of their decay were measured in aqueous perchloric acid and sodium hydroxide solutions and also as in acetic acid, biphosphate ion, tris(hydroxym
对苯二酚α-苯甲基(7)和对苯醌α,α-二苯甲基(8)是通过对羟基-α-苯基苯甲醇(9,R 1 = Ph,R 2 = H)的快速光解脱水制得的。对羟基-α,α-二苯基苄醇(9,R 1 = R 2 分别在高氯酸水溶液和氢氧化钠溶液中以及在乙酸,二磷酸根离子,三(羟甲基)甲基铵离子,铵离子和碳酸氢根离子缓冲液中测量其衰减速率。这些数据提供的这些醌甲基化物的水合速率分布图显示了hydro离子和氢氧根离子催化的区域以及“未催化的”水反应,在稀溶液中对于二苯基取代的底物饱和了nium离子的催化,但仅在浓缩状态下有效。碱性较低的单苯基底物的酸性溶液。两种底物也都具有相反的水合氢离子同位素效应(k H + / k D + <1)。这些结果表明,氢醌离子催化的反应是通过醌甲基化物在其羰基氧原子上的快速预平衡质子化,然后确定由水形成的苄型碳正离子的捕获率而发生的。苯基取代会延迟水合速率,还会降低醌甲基