Kinetics and mechanism for the formation ofo-carboxy(N-methyl)-benzohydroxamic acid in the cleavage of ethylN-[o-(N-methyl-N-hydroxycarbamoyl)-benzoyl]carbamate inN-methylhydroxylamine, acetate, and phosphate buffers
作者:M. Niyaz Khan
DOI:10.1002/kin.10142
日期:——
respectively. Both rate constants k1 obs and k2 obs showed the presence of buffer catalysis, but buffer catalysis turned out to be weak in the presence N-methylhydroxylamine buffer, while it was strong in the presence of acetate and phosphate ones. Buffer-independent rate constants k10 and k20 increased linearly with the increase in aOH with definite intercepts. The values of molar absorption coefficient of
N-[o-(N-甲基-N-羟基氨基甲酰基)苯甲酰基]-氨基甲酸乙酯 (ENMBC) 在含有 N-甲基羟胺、乙酸盐 + N-甲基羟胺和磷酸盐 + N-甲基羟胺的缓冲溶液中的裂解速率遵循不可逆连续反应路径:ENMBC 其中A和B分别代表ENMBC和邻-(N-甲基-N-羟基氨基甲酰基)苯甲酸的N-羟基环化产物。速率常数 k1 obs 和 k2 obs 都表明存在缓冲催化,但在 N-甲基羟胺缓冲液存在下缓冲催化较弱,而在乙酸盐和磷酸盐存在下则强。与缓冲液无关的速率常数 k10 和 k20 随着 aOH 的增加呈线性增加,具有明确的截距。A的摩尔吸光系数值,在恒定 pH 值下不同总缓冲液浓度下获得的结果表明存在快速平衡:A + CH3NHOH ⇆ C,其中 C 代表 N-[o-(N-甲基-N-羟基氨基甲酰基)甲基]苯异羟肟酸。© 2003 Wiley Periodicals, Inc. Int J Chem