(艹屈)和5-甲基(艹屈)的ab initio计算

湾区非角环上的甲基取代能大大增加多环芳烃的致癌性,量子化学的从头计算(ab initio)指出,5-甲基(艹屈)C1-C2键的电子性质有利于在此健发生亲电反应,电子密度分布图说明5-甲基(艹屈)在C1—C2键周围的电子密度明显大于(艹屈)相应部分的电子密度,这也有利于亲电试剂的进攻,因而在代谢过程中,5-甲基(艹屈)容易在此位置发生亲电氧化形成环氧化物,进而形成终致癌剂,这就使5-甲基(艹屈)的致癌性比(艹屈)大大增强。

AB INITIO COMPUTATIONS OF CHRYSENE AND 5-METHYLCHRYSENE

The substitution of a methyl group on a nonbenzo bay-region site of a polycyclic aromatic hydrocarbon can greatly enhance its carcinogenic activity. Ab initio computations of chrysene and 5-methylchrysene show that the electron properties of C1-C2 bond of 5-methylchrysene are favorable for an electrophilic reaction. Electron density maps indicate that electron density around C1-C2 bond of 5-methylchrysene is is higher than that of the similar part of chrysene, which also shows that the C1-C2 boud of 5-methylchrysene attacked by electrophilic agent more easily. Therefore, 5-methylchrysene is easily oxidized to form an epoxide in C1-C2 bond and to form an ultimate carcinogen during metabolism.These effects result in much higher carcinogenicity of 5-methylchrysene than that of chrysene.