Isotope effects on magnetic shielding constants have been well studied, and for the most part, are well understood. For example, the one bond deuterium isotope shift in gaseous methane, 1ΔC(2H) is approximately +0.187 ppm per deuterium and largely additive (M. Alei and W.E. Wageman, J. Chem. Phys., 1978, 68, 783). The increased shielding of the carbon nucleus with deuterium substitution results from differences in the rovibrationally structure of CH4 and CH3D (H.J. Osten and C.J. Jameson, J. Chem. Phys., 1984, 81, 4288). Two-bond deuterium isotope effects on carbon shielding, 2ΔC(2H), are generally smaller than one-bond isotope shifts, for example in benzene-d1, 1ΔC(2H) = +0.289 ppm and 2ΔC(2H) = +0.110 (R.A. Bell et al., Chem. Comm., 1972, 62). Interestingly, intramolecular hydrogen bonding often leads to much larger values of 2ΔC(2H); e.g., for dibenzolymethane, 2ΔC(O2H) is 0.59 ppm (P.E. Hansen, Magn. Reson. Chem., 1986, 24, 903)! The detailed interpretation of isotope shifts in intramolecular hydrogen bonded systems such as the enol isomer of these β-diketones is complicated because one has a double-well potential, often an unsymmetrical double-well (S. Forsén et al., J. Am. Chem. Soc., 1978, 100, 8264). We have used high-resolution 13C solid-state NMR to measure 2ΔC(O2H) values in several molecules that contain intramolecular hydrogen bonds. We will compare the solid-state results with those obtained in solution and address the question, is there a relationship between hydrogen-bond strength and isotope shifts? In the solid-state, the enol isomers of most β-diketones such as dibenzoylmethane and curcumin lose their C2 symmetry (e.g., see REW et al., J. Phys. Chem. B, 2016, 120, 11692), thus two separate values of 2ΔC(O2H) can be measured. In solutions, rapid H/D exchange between the two oxygen donors guarantees that symmetry is retained.