On the assignment of 13C resonances in unsymmetrical ortho‐disubstituted benzene rings. 13C N.m.r. spectrum of Piroxicam

Abstract

AbstractCharacteristic differences in multiplet hyperfine structure observed in coupled 13C n.m.r. spectra of symmetrical o‐disubstituted benzene rings are explained on general grounds. Contrary to earlier proposals, the observation of this effect in unsymmetrical systems is not a suitable basis for corresponding 13C n.m.r. assignments unless the proton spectrum has been sufficiently analyzed. The 13C spectrum of piroxicam, an antiinflammatory agent, is assigned and some interesting relaxation properties are noted.