The 13C and 13C DEPT Spectrum of "Acetone-d6"

A student recently asked me why her solvent resonance for acetone-d₆ was showing up in her ¹³C DEPT spectrum. Since the methyls of acetone-d₆ have no protons they will not show up in a DEPT spectrum however, the solvent is typically bought at 99.9 atom % deuterium which means that there is a very small amount of acetone-d₅ (CD₃ - CO - CD₂H). The - CD₂H group will show up as a positive signal. Both ¹³C and ¹³C DEPT spectra are shown below for "acetone-d₆". In the ¹³C spectrum in the bottom trace, one can see the expected 1:3:6:7:6:3:1 septet for a spin I = 1/2 nucleus coupled to three equivalent spin I = 1 nuclei. In the DEPT spectrum in the upper trace one sees only the small fraction of protonated carbons and the spectrum is a 1:2:3:2:1 quintet resulting from a spin I = 1/2 nucleus coupled to two equivalent spin I = 1 nuclei. One can also see the isotope effect of 0.254 ppm between the two isotopomers. Although the quintet is also present in the ¹³C spectrum, it is not seen simply because it is too small in comparison to the septet.