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NMR 2 (2009) Key - 2 signal 2 J HbHc H 3 N O O-H a H b H c...

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Phenylalanine Spectral Problem 1 H NMR Spectrum Analysis 13 C NMR Spectrum Prediction The two doublet of doublet signals at 2.95 and 3.15 ppm are the diastereotopic H b and H c protons of the CH 2 group. We cannot tell which is which. The 2 J geminal coupling is large and the vicinal coupling to the adjacent CH is medium. The doublet of doublet signal at 3.85 ppm is the CH a . The two vicinal couplings ( 3 J ) to the adjacent diastereotopic protons of the CH 2 are medium AND SIMILAR in size. Thus it almost looks like a triplet. The broad signal at 4.6 ppm is the acid, amino, and water signal. (All exchangable protons.) Since the acid group is acidic and the amino group is basic, we would expect to see one R-NH 3 + signal and NOT one acid signal and one R-NH
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Unformatted text preview: 2 signal. 2 J HbHc + H 3 N O O-H a H b H c H b H c H a 2 J HbHc 3 J HaHb 3 J HaHc H d H e H f H d H e 3 J HaHb 3 J HaHc + H 3 N O O-174.24 56.94 37.21 136.30 129.91 130.19 128.42 The multiple signals at 7.2 ppm are the aryl protons. We can see one doublet signal (right side of group) for the two H d protons. The two H e protons (doubllet of doublets) and one H f (doubllet of doublets) are overlapping. By symmetry these two are the same as 129.91 and 130.19 Tryptophan DEPT 13 C NMR Problem N H COO NH 3 DEPT 13 C NMR Problem: Assign signals as C, CH, CH 2 , CH 3 26 ppm CH 2 54 ppm CH 107 ppm C 111 ppm CH 118 ppm CH 119 ppm CH 121 ppm CH 124 ppm CH 126 ppm C 136 ppm C 174 ppm C...
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