1982 年 30 巻 7 号 p. 2534-2543
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.
