Quantum chemical calculation of conformations and rotation barriers of functional groups in arylsulfonyl halides

The semiempirical PM3 method is used to calculate the potential functions o f internal rotation of the functional groups -SO2Cl -NO2, -CH3, -OCH3, and -NH2 of benzenesulfonyl halide molecules (PhSO(2)Hal, Hal = F, Cl, Br, I) a nd twelve substituted derivatives of benzenesulfonyl chloride. Molecular co nformations have been determined and internal rotation barriers of the func tional groups have been calculated. For meta- and para-substituted benzenes ulfonyl chlorides, the projection of the S-Hal bond is perpendicular to the plane of the benzene ring. The rotation barriers of the -SO(2)Hal group of benzenesulfonyl halides increase in the series Hal = F, Cl, Br, I. The rot ation barriers of the -SO2Cl group of benzenesulfonyl chloride with meta- a nd para-substituents slightly increase with the electron-donor properties o f the substituent. The rotation barriers of the functional groups of ortho- substituted benzenesulfonyl chlorides are 3 or 4 times as high as those of the meta- and para-isomers. For pam-substituted benzenesulfonyl chlorides, the rotation barriers of the functional groups increase in the order -CH3, -NO2, SO2Cl, -OCH3, -NH2.