Pyramidalization at the sp2‐Hybridized ipso‐Carbon Atom of Phenyl Compounds

Abstract

AbstractIn this study we investigate the pyramidalization of the sp2‐hybridized center at the ipso‐carbon atom Ci of phenyl compounds on the theoretical side by DFT calculations of toluene, t‐butylbenzene, and ethylbenzene and on the experimental side by a scatter plot analysis of 14,169 structures of ethylbenzene compounds Cβ−CαH2−C6H5 with three open positions for variation at Cβ, accumulated in the Cambridge Structural Database. In a 360° rotation about the bond between Cα of the substituent and the ipso‐carbon atom Ci of the phenyl ring, the pyramidalization performs three maxima and minima. A comparison of structures with pyramidalization and its hypothetical counterparts without pyramidalization shows that pyramidalization is associated with a gain of energy. The data reveal that it is the carbon atom Cα of the phenyl substituent, which on pyramidalization bends away from the phenyl plane. Pyramidalization of sp2‐hybridized centers is an omnipresent member in molecular weak interactions.