13C NMR Spectroscopy for the Quantitative Determination of Compound Ratios and Polymer End Groups

C-13 NMR spectroscopic integration employing short relaxation delays was evaluated as a quantitative tool to obtain ratios of diastereomers, regioisomers, constitutional isomers, mixtures of unrelated compounds, peptoids, and sugars. The results were compared to established quantitative methods such as H-1 NMR spectroscopic integration, gas chromatography, and high-performance liquid chromatography and were found to be within <3.4% of H-1 NMR spectroscopic values (most examples give results within <2%). Acquisition of the spectra took 2-30 min on as little as 10 mg of sample, proving the general utility of the technique. The simple protocol was extended to include end group analysis of low molecular weight polymers, which afforded results in accordance with H-1 NMR spectroscopy and matrix-assisted laser desorption-ionization time-of-flight spectrometry.