Demixing of severely overlapped 1H NMR resonances and interpretation of anomalous intensity pattern of dipolar coupled A3 spins in a weakly aligning medium

Abstract

We report a single 13C spin edited selective proton–proton correlation experiment to decipher overcrowded 13C coupled proton NMR spectra of weakly dipolar coupled spin systems. The experiment unravels the masked 13C satellites in proton spectrum and permits the measurement of one bond carbon–proton residual dipolar couplings in I 3S and for each diastereotopic proton in I 2S groups. It also provides all the possible homonuclear proton–proton residual couplings which are otherwise difficult to extract from the broad and featureless one dimensional 1H spectrum, in addition to enantiodifferentiation in a chiral molecule. Employment of heteronuclear ( 13C) decoupling in the evolution period results in complete demixing of overlapped signals from enantiomers. The observed anomalous intensity pattern in strongly dipolar coupled methyl protons in methyl selective correlation experiment has been interpreted using polarization operator formalism.