酚类化合物苯环碳原子的化学位移与其净电荷的关系(Ⅰ)——除酚羟基外无其他取代基的酚

RELATION BETWEEN THE CHEMICAL SHIFT OF A CARBON ATOM ON THE BENZENE RING OF A PHENOLIC COMPOUND AND ITS NET CHARGE (Ⅰ) —— PHENOLIC COMPOUNDS WITH ONLY PHENOLIC HYDROXYL GROUPS NO OTHER SUBSTITUENTS

用AB INITIO法对只含酚羟基的 7种酚化合物的苯环碳原子 (Ci)的净电荷 (Qi)做了计算 ,并测定或查阅了它们的13CNMR谱 ,参考标准图谱找出了Ci 对应的化学位移δi,发现Qi δi间呈现较好的线性关系 .每种化合物均有最负净电荷 (Qmin)与最低化学位移 (δmin) ,Qmin与δmin出现在酚羟基邻位同一碳原子上 ,而这一碳原子具有最大的亲核亲电反应活性 .那些δi>130的碳原子反应活性极小 ,以至不能发生亲核亲电反应 .在酸、碱条件下会改变酚化合物的电荷分布和化学位移 ,因而其反应活性也随之改变 .

With AB INITIO method, the net charge ( Q i ) values of the carbon atoms on the benzene rings of seven kinds of phenolic compounds are calculated, which have only phenolic hydroxyl group. Their 13 CNMR spectra are tested or consulted. With the standard spectra, the corresponding δ i value of C i is found. Moreover, it is found that there is good linear relation between Q i and δ i . Every compound has the most negative net charge value ( Q min ) and the lowest chemical shift value ( δ min ). Q min and δ min are found to belong to the same carbon atom which is on ortho position of phenolic hydroxyl group, then the carbon atom has the highest reactivity in nucleophilic electrophilic reaction. While the δ i value of a carbon atom < 130, the reactivity of the carbon atom is so low that it can not occur nucleophilic electrophilic reaction. On acidic or alkaline condition, the charge distribution of a phenol compound and the chemical shifts of carbon atoms in the compound will be altered, then the reactivity of the carbon atoms will change also.