INADEQUATE NMR Experiment* 13 C- 13 C Coupling I ncredible N atural A bundance D oubl E QUA ntum T ransfer E xperiment (INADEQUATE) is a 2D NMR experiment that reveals 1 J CC correlations but can be tuned for two- and three-bond correlations in a carbon chain or through a heteroatom in the molecule. The spectrum looks different than the other 2D spectra. The f2 axis is the carbon chemical shift and the f1 axis is the double quantum frequency (the sum of the two correlating frequencies). There is no diagonal signal. Each cross-peak is a doublet split by carbon-carbon coupling. The correlation is often shown as a line connecting the doublet. *All spectra in this unit are simulated. Example: Ethyl benzene Drawbacks to INADEQUATE While this technique could be tremendously useful for determining which signals arise from neighboring carbons. Unfortunately, it is very insensitive as 13 C isotope is __________% of the carbons at natural abundance. The odds of finding a 13 C next to another 13 C in a molecule is extremely [ likely / unlikely ] . Because of the insensitivity of the experiment, it requires a long time with many scans and/or [ large / small ] quantities of sample. Suggest a possible change to your compounds that could increase the ability to run this INADEQUATE experiment on your compound at a normal sample concentration. Assign Carbons This is a simulated INADEQUATE spectrum of 1-octanol. The peaks are numbered from left to right on the 13 C NMR spectrum. Using the correlations, assign the carbons to the structure below. Distinguish Isomers Researchers performed a photocatalytic hydroxymethylation (below) which yielded one pure product. But they were unsure which of the two possible isomers was obtained. An INADEQUATE NMR experiment was used to determine the correct isomer. R. D. Cohen, J. Saurí C.A. Huff, S.W. Krska, G.E. Martin, Magn. Reson. Chem. 2016. DOI: 10.1002/mrc.4470 Using the data provided, determine which isomer was formed. Add the correct numbering to the structure below. Add the hydroxy methyl group in the correct location. Show the correlations as double-headed arrows on the structure. INADEQUATE Key Correlations: C6 \(\leftarrow \rightarrow\) C=O C5 \(\leftarrow \rightarrow\) C6 C2 \(\leftarrow \rightarrow\) C3 C3 \(\leftarrow \rightarrow\) C4