Theoretical study of the ortho, meta and para substitution of different electron withdrawing functional groups in phenol derivatives

Even though aromaticity cannot be directly probed, it has, nevertheless, traditionally been associated withat least three types of measurable molecular effects: structural, energetic and magnetic. In this study the role of ortho,meta and para situation of different electron withdrawing functional groups on the electronic structure and aromaticityof phenol molecule has been investigated. Geometry of considered phenol derivatives have been optimized inB3LYP/6-311++G** level of theory. Results show that, the stability of ortho isomers of various substituted phenols aremore than meta and para isomers. In addition, ortho isomers have more acidic characteristic, comparing with meta andpara substituted derivatives of phenol. The natural charges confirm this statement. On the other hand, when functionalgroups sit on meta position, NICS (1)ZZ values are close together, no matter what is the functional group. But differentfunctional groups cause to different NICS (1)ZZ for benzene ring, when they sit on the ortho position. In ortho position,COCH3 substituted phenol have the most aromaticity. CN and CHO functionalized phenol are in the next orders.

Keywords:

substitution effect , electron withdrawing groups , phenol , NICS