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Chapter 13: Q2P (page 656)

Predict the chemical shifts of the protons in the following compounds

Short Answer

Expert verified

Alkene hydrogens give nearly 5.5 ppm NMR chemical shift. And the sp3hybridised carbon hydrogen give 0.8 ppm in NMR spectra.







Step by step solution

01

Alkene and sp3hydrogens

Alkene hydrogens give nearly 5.5 ppm NMR chemical shift. And the sp3hybridised carbon hydrogen give 0.8 ppm in NMR spectra.

02

 Phenyl and methyl hydrogens

Phenyl hydrogens give 7 ppm NMR chemical shift. And the methyl hybridised carbon hydrogen give 2.5 ppm in NMR spectra.

03

 Phenyl and methoxy hydrogens

Phenyl hydrogens give 7 ppm NMR chemical shift. And the methoxy hydrogen give 3.8 ppm in NMR spectra.

04

Alkene and Alkyne hydrogens

Alkene hydrogens give 5.5 ppm NMR chemical shift. And the alkyne carbon hydrogen give 2 ppm in NMR spectra.

05

Phenyl, carboxylic acid and methyl hydrogens

Phenyl hydrogens give 7 ppm NMR chemical shift. And the carboxylic acid carbon hydrogen give 13 ppm in NMR spectra and methyl is 2.5 ppm.

06

Methyl hydrogens

Methyl hydrogens give 1.8 ppm NMR chemical shift. But in presence of bromine the value is deshielded and increases near to 3.7 ppm in NMR spectra.

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Most popular questions from this chapter

(A true story.) A major university was designated as a national nuclear magnetic resonance center by the National Science Foundation. Several large superconducting instruments were being installed when a government safety inspector appeared and demanded to know what provisions were being made to handle the nuclear waste produced by these instruments. Assume you are the manager of the NMR center and offer an explanation that could be understood by a nonscientist.

Draw a splitting tree, similar to Figures 13-32 and 13-33, for proton Hc in styrene. What is the chemical shift of proton Hc?

A small pilot was adding bromine across the double bond of but-2-ene to make 2,3-dibromobutane. A controller malfunction allowed the reaction temperature to rise beyond safe limits. A careful distillation of the product showed that several impurities had formed, including the one having the NMR spectra that appear below. Determine its structure and assign the peaks to the protons in your structure.

Hexamethylbenzene undergoes radical bromination with N-bromosuccinimide to give one monobrominated product (C12H17Br) and four dibrominated products (C12H16Br2). These products are easily separated by GC-MS, but the dibrominated products are difficult to distinguish by their mass spectra. Draw the monobrominated product and the four dibrominated products and explain how 13C NMR would easily distinguish among these compounds .

Phenyl Grignard reagent adds to 2-methylpropanal to give the secondary alcohol shown. The proton NMR of 2-methylpropanal shows the two methyl groups as equivalent (one doublet at δ 1.1), yet the product alcohol, a racemic mixture, shows two different 3H doublets, one at δ 0.75 and one around δ 1.0

(a)Draw a Newmann projection of the product along the C1-C2 axis.
(b)Explain why the two methyl groups have different NMR chemical shifts. What is the term applied to protons such as these?
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