Lubrication of an apparatus with silicone grease may result in the reaction mixture being contaminated with the grease. The impurity may be carried through purification by chromatography in undesirable amounts. In NMR spectroscopy, the methyl groups in polydimethylsiloxane display 1H and 13C chemical shifts similar to trimethylsilane (TMS), the reference compound for those forms of NMR spectroscopy. As with TMS, the signal is a singlet. In 1H NMR, silicone grease appears at a singlet at δ = 0.07 ppm in CDCl3, 0.09 in CD3CN, 0.29 in C6D6, and −0.06 ppm in (CD3)2SO. In 13C NMR, it appears at δ = 1.19 ppm in CDCl3 and 1.38 ppm in C6D6. Tables of impurities commonly found in NMR spectroscopy have been prepared, and such tables include silicone grease.