Question

How to distinguish between the two members of each pair of compounds by C-NMR?

4. (12 points) By citing specific data, show that you could (or could not) distinguish between the members of each pair of compounds by 13C-NMR Spectroscopy. If you are aware of several significant distinguishing features, mention all of them. Give all references used to answer the question. a) 1-phenyl-2-pentanone 1-phenyl-1-pentanone

Answer 1

All the 13C spectrums are refered from chemicalbook website. You can search with the search terms in this combination: "name of compound" + 13C NMR CH3 H E 1-phenyl-1-pentanone ср в АОн сня 1-PHENYL-2-PENTANONE 208: A 134: B 129: C 128: D 126: E 50: F 43: G 17: H 13:1 200: A 137: B 132: C 128: D 128: E 38: F 26: G 22: H 13:1 The carbonyl in second compound is in conjugation with phenyl ring and hence its peak is little upfield and the ring carbons are also showing different peaks respectively.

W е А ОН A OH 0 SO 3-iodobenzoic acid 5 (ppm) 131: D 136: C 92: G 127: F 138: B 128: E 165: A 3-bromobenzoic acid o (ppm) 166: A 130: E 121: G 131: D 133: B 132: C 128: F In this case due to electron donation resonance effect of iodine is predominant and hence ring carbon bearing iodine is most up field and it is distinctly below 100ppm even if it is sp2 carbon. Such is not the case in bromo bearing ring carbon.