Kinetics and mechanism of base-catalysed degradations of substituted aryl-N-hydroxycarbamates, their N-methyl and N-phenyl analogues
作者:Petr Beier、Jaromír Mindl、Vojeslav Štěrba、Jiří Hanusek
DOI:10.1039/b310454k
日期:——
The kinetics and mechanism of the degradation reactions of substituted phenyl N-hydroxycarbamates and their N-methyl and N-phenyl analogues have been studied at pseudo-first-order reaction conditions in aqueous buffers and sodium hydroxide solutions at 20 [degree]C and 60 [degree]C and at I= 1 mol[middle dot]l(-1). The dependence of log k(obs) on pH for phenyl N-hydroxycarbamates at pH < 9 and pH >
已在拟一级反应条件下,在水性缓冲液和氢氧化钠溶液中,于20℃和60℃,在拟一级反应条件下研究了取代的苯基N-羟基氨基甲酸酯及其N-甲基和N-苯基类似物的降解反应的动力学和机理。 ℃,在I = 1mol时,中点l(-1)。在pH <9和pH> 13时,N-羟基氨基甲酸苯酯的log k(obs)对pH的依赖性与单位斜率呈线性关系。在pH 10-12时,log k(obs)与pH无关。布朗斯台德系数β(lg)约为-1(pH 7-13)和-1.53(pH> 13),表明N-羟基氨基甲酸酯苯基的降解反应遵循E1cB机理,给出了相应的苯酚/酚盐和HO -N [双键,长度为m-破折号] C [双键,长度为m-破折号O。后面的物质经过进一步分解,生成碳酸盐,氮气和氨水作为最终产品。与苯基N-羟基氨基甲酸酯相反,在pH 7-9下,N-甲基衍生物通过一致的机理降解为相应的苯酚/苯酚酸酯,碳酸酯和甲胺(小β(1g)约为-0