Solvents for NMR spectroscopy

A common solvent for dissolving compounds for 1H and 13C NMR spectroscopy is deuteriochloroform, DCCl3. In 1H NMR spectra, the impurity of HCCl3 in DCCl3 gives a small signal at 7.2 ppm (see spectrum of methyl propanoate). In 13C spectroscopy 1.1% of the deuteriochloroform has a 13C isotope and it is bonded to a deuterium atom. The nucleus of the deuterium atom, the deuteron, has a more complicated nuclear spin than does the proton, and it has a gyromagnetic ratio () 1/6 as large. This more complicated nuclear spin gives rise to three spin states instead of the two spin states for the proton, and the deuteron undergoes resonance at a different frequency than either the proton or 13C nucleus. These spin states are approximately all equally populated. Because the spin-spin coupling between the 13C and the deuterium is not eliminated during proton decoupling, the DCCl3 shows three equal peaks of low to moderate intensity at about 77 ppm (see Figure 13). The separation is the carbon-deuterium coupling constant JCD. The intensity is low to moderate because the 13C receives no Nuclear Overhauser Enhancement from the proton decoupling.

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Copyright information: Original content © University of Colorado, Boulder, Chemistry and Biochemistry Department, 2011. The information on these pages is available for academic use without restriction.