A Study of steric and electronic effects in some methane- and dimethane-sulphonanilides by 13C NMR spectroscopy

✍ Scribed by Misbah Ul Hasan; Sk. Asrof Ali

• Publisher: John Wiley and Sons
• Year: 1985
• Tongue: English
• Weight: 498 KB
• Volume: 23
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260230109

✦ Synopsis

The steric and electronic interactions in several methanesulphonanilides and dimethane-sulphonanilides have been examined on the basis of their =C NMR chemical shifts. In aromatic amines there is evidence of nitrogen electron pair donation into the aromatic ring. However, the substitution of a methanesulphonyl group on nitrogen, as in N-phenylmethanesulphonamide, causes a decrease in this resonance interaction. The chemical shifts of orthoand para-carbons therefore move downfield in comparison with the corresponding amines. Substitution of the aromatic ring at the para position by electron-withdrawing and electron-donating groups affects the resonance process. The substitution of methyl groups either at nitrogen or at the ortho positions causes severe steric inhibition of resonance, which is dearly reflected in the chemical shifts of these compounds. The chemical shifts in several dimethane-sulphonanilides have also been examined and compared with the shifts in the corresponding methanesulphoddes. The observed Werences are explained in terms of steric, mesomeric and inductive interactions in these molecules. The preferred conformations of these compounds in solution are also postulated on the basis of their chemical shifts.