芳杂环亲电取代活性的研究

THE STUDY OF THE ACTIVITY OF AROMATIC AND HETEROAROMATIC COMPOUNDS TOWARDS ELECTROPHILIC SUBSTITUTION REACTIONS

芳杂环的亲电取代活性及定位效应是许多理论研究的对象。研究的重点多是同系物间的活性比较及分子内的取代定位效应。其规律往往用反应活性部位的电荷数量及分布来解释。量子化学计算结果,一般也符合物理有机的这一传统解释。因此,电荷数量及分布决定分子的取代活性及定位仍是有机化学中普遍接受的观点。不少量子化学活性指标也用于亲电取代活性及定位效应的解释,但一般只局限于同系物的比较,不同母核的芳杂环的亲电取代活性比较则较少为人们所注意。

The order of the activity of 5 aromatic and heteroaromatic compounds towars electrophilic substitution reaction was determined,namely,anthrac-ene-thiophene>naphthalene>benzene>pyridine.CNDO/2 calculations show that the activity order and the orientation of aromatic and heteroaromatic compounds towards the electrophilic substitution reactions were not determined by the charge distribution,but by theπ-electron polarizability(superdelocalizability)of the reaction sites.