Ressonância Magnética Nuclear

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210 Chapter 10 USING NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY TO DEDUCE STRUCTURE (d) doublet of doublets, the doublet splitting with the cis being larger than that to the trans Hb; a doublet of for the same reason: The doublet splitting with the cis Hₐ is larger than that to the trans Hₐ Br Br (e) because the geminal splitting with Hb is about the same as splitting with the trans Hc; doublet of doublets, the doublet splitting with the cis being larger than the geminal split- ting to doublet of doublets, the doublet splitting with the (cis) Hb being larger than that to the (trans) Hₐ. Hb Hc Br Br Br 53. Determine how many different signals would be displayed by each isomer. Pentanes: 3 signals C c-c-c 4 signals C C c-c-c 2 signals C All three can be readily identified by ¹³C NMR. Hexanes: 3 signals C 5 signals C 4 signals* C C C 2 signals C C C 4 signals* C The NMR spectra of 3-methylpentane and 2.2-dimethylbutane (marked with asterisks) are each having four different carbon environments. The two spectra must be distinguished by signal intensities: 2.2-dimethylbutane has three equivalent methyl which give rise to an exceptionally intense signal.