The stability of carboquone in aqueous solution. II. Kinetics and mechanisms of degradation of 2,5-bis(1-aziridinyl)-3,6-dimethyl-1,4-benzoquinone and 2,5-bis-(1-aziridinyl)-3,6-diisopropyl-1,4-benzoquinone in aqueous solution.
作者:AKIRA KUSAI、SEIJI TANAKA、SEIGO UEDA
DOI:10.1248/cpb.30.2534
日期:——
The kinetics and mechanisms of the degradation of 2, 5-bis (1-aziridinyl)-3, 6-dimethyl-1, 4-benzoquinone (MEB) and 2, 5-bis (1-aziridinyl)-3, 6-diisopropyl-1, 4-benzoquinone (IPEB) were investigated and compared with those of 2, 5-bis (1-aziridinyl)-1, 4-benzoquinone (EB) investigated previously. The degradation of MEB and IPEB follows pseudo first-order kinetics in the same way as that of EB. The pH-rate profiles showed slopes of -1 on the acidic side and +1 on the basic side, as did that of EB. Thus, the degradation of MEB and IPEB is subject to specific acid-base catalysis. The apparent activation energies for MEB degradation at pH 4 and pH 11 were 16 and 24 kcal/mol, and those for IPEB degradation were 17 and 23 kcal/mol, respectively. In basic aqueous solution, MEB and IPEB are degraded to dihydroxybenzoquinones with monohydroxy-mono (1-aziridinyl) benzoquinones as intermediates in the same way as EB. On the other hand, in acidic aqueous solution, (2-hydroxyethylamino) benzoquinones are produced from MEB and IPEB, as in the case of EB, but they are further degraded to hydroxybenzoquinones. This was not practically observed in the case of EB. This phenomenon can be explained as follows : the alkyl groups at the 3 and 6 positions of benzoquinone increase the relative hydrolysis rate of 2-hydroxyethylamino groups derived from the hydrolytic cleavage of aziridine rings at the 2 and 5 positions of benzoquinone, making it comparable to the ring cleavage rate of aziridinyl groups.
研究了 2,5-双(1-氮丙啶基)-3,6-二甲基-1,4-苯醌(MEB)和 2,5-双(1-氮丙啶基)-3,6-二异丙基-1,4-苯醌(IPEB)的降解动力学和机理,并与之前研究的 2,5-双(1-氮丙啶基)-1,4-苯醌(EB)的降解动力学和机理进行了比较。MEB 和 IPEB 的降解遵循与 EB 相同的伪一阶动力学。与 EB 一样,pH-速率曲线在酸性侧的斜率为-1,在碱性侧的斜率为+1。因此,MEB 和 IPEB 的降解受特定酸碱催化作用的影响。在 pH 值为 4 和 11 时,MEB 降解的表观活化能分别为 16 和 24 kcal/mol,IPEB 降解的表观活化能分别为 17 和 23 kcal/mol。在碱性水溶液中,MEB 和 IPEB 降解为二羟基苯醌,中间产物为单羟基-单(1-氮丙啶基)苯醌,降解方式与 EB 相同。另一方面,在酸性水溶液中,与 EB 的情况一样,MEB 和 IPEB 会生成(2-羟乙氨基)苯醌,但它们会进一步降解为羟基苯醌。而在 EB 的情况下,实际上并没有观察到这种现象。这种现象可以解释如下:苯醌 3 和 6 位上的烷基提高了苯醌 2 和 5 位上的氮丙啶环水解裂解产生的 2-羟乙氨基的相对水解速度,使其与氮丙啶基的裂环速度相当。