Nuclear Magnetic Resonance Spectroscopy. Long-Range Spin-Spin Couplings Involving Carbon-13

Abstract

Relatively few studies have been reported of spin spin couplings involving carbon and atoms more than one bond removed. Such couplings can often be seen as ^(13)C satellites in spectra of the other nuclei, but unless the spectra are simple, and even if the “inner” satellites can be detected, specific coupling assignments may not be possible. In such circumstances, specific isotopic enrichment can be of great value. Carbon-fluorine and carbon-phosphorus couplings have been directly observed in the natural-abundance ^(13)C satellites. Internuclear double-resonance experiments utilizing observations of proton spectra have been used to study couplings between carbon and nondirectly bonded phosphorus and nitrogen where the proton spectra are relatively simple. We report here some nonbonded couplings between carbon and other nuclei measured directly from ^(13)C spectra in which the protons are decoupled.