chm 2120 answers 7

chm 2120 answers 7 - Assignment #7. 2009 NMR The following...

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Assignment #7. 2009 NMR The following problems reflect closely the type of NMR questions you can expect on the final exam. They vary from very basic concept and interpretation of relatively simple spectra to more complex questions, the type that you might expect towards the end of the final exam. 1. Give the number of peaks expected for the indicated hydrogens in each of the following structures; H 3 C C H 2 C H 2 CH 3 O CH 3 H ? ? ? H 3 C H 2 C C H 2 H 2 C C H 2 H 2 C O CH 3 ? ? ? a) b) H H H 3 C O H 2 c) 2 2 9 1 3 5 3 The following require an understanding that the n+1 rule does not always hold since the coupling constants between the different Hs are not necessarily the same. Cl H H CH 3 O d) ? H 2 H 3 H 1 CH 3 O ? e) ? 2 2 tiimes 2 = 4 The n+1 rules is valid when the coupling constants for all the Hs that couple to the H in question are the same. example 1 2 1 triplet when the coupling constant between ther different hydirgens is different the internal lines no longer coincide as on th eleft and the result is a doublet of doublets, that is 2X 2 or 4 lines. coupling between H1 and H3 is larger that H1 to H2. 2) Explain why the chemical shift of aromatic hydrogens occurs at much lower field than those on staturated carbon. Draw a 'picture' to illustrate your answer.
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chm 2120 answers 7 - Assignment #7. 2009 NMR The following...

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