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Chapter 13: Q13-19P (page 413)

Classify the resonances in the13C NMR spectrum of methyl propanoate,CH3CH2CO2CH3.

Short Answer

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NMR Spectra

Step by step solution

01

13C NMR spectroscopy

Most 13C resonances are between 0 and 220 ppm downfield from the TMS reference line, with the exact chemical shift of each 13C resonance dependent on that carbon’s electronic environment within the molecule.

Generally, the chemical shift is affected by the electronegativity of a nearby atom like oxygen, nitrogen, halogen, etc.

02

13C NMR spectrum for methyl propanoate

The chemical shift value for the carbonyl carbon of ester is 174.9 ppm. While the -CH3group which is attached to the oxygen has a chemical shift value of 51.5 ppm. Also, the -CH3group which is attached to -CH2group is about 9.2 ppm. The -CH2group which is connected to carbonyl carbon has a chemical shift value of 27.5 ppm.

NMR Spectra

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Most popular questions from this chapter

We saw in Section 9-3 that addition of H-Br to a terminal alkyne leads to the Markovnikov addition product, with the Br bonding to the more highly substituted carbon. How could you use 13C NMR to identify the product of theaddition of 1 equivalent of H-Br to 1-hexyne?

Is a nucleus that absorbs at 6.50 δmore shielded or less shielded than a nucleus that absorbs at 3.20 δ? Does the nucleus that absorbs at 6.5 δrequire a stronger applied field or a weaker applied field to come into resonance than the one that absorbs at 3.20 δ?

Question: When measured on a spectrometer operating at 200 MHz, chloroform (CHCl3)shows a single sharp absorption at 7.3δ.

(a)How many parts per million downfield from TMS does chloroform absorb?

(b)How many hertz downfield from TMS would chloroform absorb if the measurement were carried out on a spectrometer operating at 360 MHz?

(c)What would be the position of the chloroform absorption inδunits when measured on a 360 MHz spectrometer?

Question: Predict the number of carbon resonance lines you would expect in the C- 13 NMR spectra of the following compounds:

(a) Methylcyclopentane

(b) 1- Methylcyclohexane

(c) 1,2- Dimethylbenzene

(d) 2- Methyl-2-butene

(e)

(f)

The proton NMR spectrum of a compound with the formula C7H12O2is

shown. The infrared spectrum displays a strong band at 1738 cm-1 and

a weak band at 1689 cm-1 . The normal carbon-13 and the DEPT experimental

results are tabulated. Draw the structure of this compound.
See all solutions

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