问题 单项选择题

有关同系物化学结构对毒性影响因素的下列说法中,不正确的是()。

A.饱和脂肪烃(达到9个碳原子以后)随着碳原子数增多,麻醉作用增强

B.饱和脂肪烃甲烷和乙烷是惰性气体可引起窒息

C.不同烷烃类的毒性排列为环烃<直链烃<支链烃

D.碳原子数相同时不饱和键增加可增加其毒性,如乙烷<乙烯<乙炔

E.饱和脂肪烃(达到9个碳原子以前)随着碳原子数增多,麻醉作用增强

答案

参考答案:A

解析:饱和脂肪烃甲烷和乙烷是惰性气体,可引起窒息。随着碳原子数增多,麻醉作用增强。但达到9个碳原子之后,却又随着碳原子数增多,麻醉作用反而减弱。这是由于随着碳原子数增加而脂溶性增大,即脂水分配系数增大,易于经简单扩散透过生物膜进入组织器官发挥作用。而当碳原子数超过9个之后,脂溶性过大,不利于经水相转运,不易穿透生物膜达到靶器官。

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