Practice question

One-bond carbon-proton coupling in 13CH3Cl arises from Fermi contact interaction between directly bonded magnetic nuclei, magnitude proportional to gyromagnetic ratios and s-character, typically 125 to 160 Hz for sp3 carbon, much larger than vicinal proton-proton couplings near 7 Hz. Observed value around 140 Hz reflects strong interaction in chlorinated alkane, producing widely spaced doublet satellites in proton spectrum when decoupling absent. This large constant enables polarization transfer in INEPT and DEPT experiments, underpins HSQC sensitivity enhancement, and is exploited for carbon editing in metabolomics and protein-labeled samples.