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.

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