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We reference our signals to the solvent CDCl3 7.25ppm in the 1H spectrum, top and 77.0ppm (3 lines) in the 13C spectrum, middle. In routine 13C NMR spectra we get one signal for each chemicaly distinct carbon atom in the sample. There are no visible C-C couplings or C-H scalar couplings. DEPT-135 greatly simplifies our efforts in assignment bottom. Carbon atoms bearing 3 H atoms are positive, those with 2 H atoms are negative, those with 1 are positive and quaternary carbon atoms generate no signal. We look at all three spectra at once when we interpret.
All three spectra indicate unsaturation. In the 1H we see signals at 7.05ppm, 6.22, 6.13, 4.97, 5.03. In the 13C/DEPT we have single H bearing C's at 153.9ppm, 127.7, 122.7, and an unsaturated C at 112.4 bearing 2H's. We also have two sp2 quaterany C's at 167.1 and 145.2. Most notably we see two keto groups n the 13C spectrum, a conjugated one at 186.3 and a non conjugated one at 219.5. By looking at the coupling patterns in the 1H spectrum and with a little prior knowledge of steroid chemistry and 13C chemical shifts we can assign the signals. We'll jump ahead and show the assignments.
Notice that we put the conjugated keto at C-3 and the unconjuged one at C-17. Exocylic methylene groups are rare and we put it at C-6 previous page.
2D methods are very powerful tools in that they alow the spectroscopist to determine connectivities. 2D spectra have three dimensions, chemical shifts in the X (F2) and Y (F1) and amplitude comming out and going below the plane.
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