The effect of the methoxy group on the geometry of the benzene ring supported by crystal structure studies and Ab Initio Calculations. Crystal and Molecular Structure of 4-(4-Methoxyphenyl)-2,6-diphenylpyridine and 1-Methyl-4-(4-methoxy-phenyl)-2,6-diphenylpyridinium perchlorate.

Abstract

Crystal and molecular structures of 4-(4-methoxyphenyl)-2,6-diphenylpyridine (I) and 1-methyl-4-(4-methoxyphenyl)-2,6-diphenyl pyridinium perchlorate (II) are repoded, with R=0.052 and 0.070, respectively. The lower precision of II is due to disorder of the perchlorate anion. A geometrical analysis of 8 p-substituted derivatives of anisole shows that the methoxy group interacts strongly with the ring via the resonance effect. Significant deformations of the exo-cyclic bond angles at MeO- substituted carbon atom are due to steric hinderance between ortho CH and Me group. Ab initio calculations for anisole are in line with the observed planar conformation of these systems. The difference in energy between the planar and perpendicular conformers is 1.4 kcal/mole at the 6-31G* level. The intramolocular interactions between the -OMe group and C ipso-C orthoH are explored through additional ab initio calculations. They induce more double character of C ipso-C ortho bond, thereby causing one Kekule structure to be preferred.