Flash Photolytic Generation of <i>o</i><i>rtho</i>-Quinone Methide in Aqueous Solution and Study of Its Chemistry in that Medium
作者:Y. Chiang、A. J. Kresge、Y. Zhu
DOI:10.1021/ja010826g
日期:2001.8.1
Flash photolysis of o-hydroxybenzyl alcohol, o-hydroxybenzyl p-cyanophenyl ether, and (o-hydroxybenzyl)trimethylammonium iodide in aqueous perchloric acid and sodium hydroxide solutions, and in acetic acid and biphosphate ion buffers, produced o-quinone methide as a short-lived transient species that underwent hydration back to benzyl alcohol in hydrogen-ion catalyzed (k(H+) = 8.4 x 10(5) M(-1) s(-1))
邻羟基苄醇、邻羟基苄基对氰基苯基醚和(邻羟基苄基)三甲基碘化铵在高氯酸和氢氧化钠水溶液以及乙酸和磷酸氢盐离子缓冲液中的闪光光解,产生邻醌甲基化物作为短链-在氢离子催化 (k(H+) = 8.4 x 10(5) M(-1) s(-1)) 和氢氧根离子催化 (k(H2O)- = 3.0 x 10(4) M(-1) s(-1)) 反应以及未催化的 (k(UC) = 2.6 x 10(2) s(-1)) 过程。氢离子催化反应得到溶剂同位素效应 k(H+)/k(D)+ = 0.42,其逆性质表明该过程是通过醌甲基化物的羰基氧原子的快速可逆平衡质子化而发生的,然后是由水产生的碳正离子的定速捕获。另一方面,未催化反应的速率常数的大小表明该过程是通过将水简单地亲核加成到醌甲基化物的亚甲基而发生的。乙酸缓冲液通过酸和碱催化途径也加速了醌甲基化物的衰变,对这些溶液中形成的反应产物的定量分析表明,这种加速是由乙