The Gauche‐Effect in 1,2‐Bis(arylsulfonate)ethanes

With an aim of obtaining a fundamental understanding of C−C bond conformation theory, the molecular structure of an ethane with electron‐withdrawing groups, 1,2‐bis(4‐methoxybenzene‐sulfonate)ethane, was elucidated. According to the general conformation rule for alkanes, which states that molecules adopt a stabilized structure to avoid steric repulsion, ethanes typically adopt anti ‐conformation. However, the title compound exhibited gauche ‐conformation, as revealed by a single crystal diffraction study. Theoretical studies also support this behavior. Natural Bond Orbital (NBO) analysis suggests that the orbital interaction between the σ* CO orbital, attributable to the sulfonate groups, and the adjacent σ CH orbital stabilizes the gauche ‐conformation. The authors conclude that the sulfonate group acts as a gauche ‐effect synthon, which is widely applicable in organic chemistry.