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Wize University Chemistry Textbook > Structure Elucidation (IR Spectroscopy, NMR, Mass Spectrometry)

13C NMR

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Carbon (13C) NMR


For organic compounds the 13C isotope is 1% abundant, so while 13C NMR is useful for a range of organic molecules it can be easier with more concentration solutions. For best results, a larger amount of sample (20-50 mg) is dissolved in 0.7-1 mL of deuterated solvent, such as CDCl3 or C6D6 (so you can still run a 1H NMR if you need!).

Do you expect to see C-C coupling in 13C NMR?



The residual solvent peak for CDCl3 is a triplet at 77 ppm in 13C NMR, why?


Often 13C NMR data is just given as a the number of peaks (e.g. compound X has 6 signals in its 13C NMR spectrum). Each unique carbon environment will produce a different signal. With that in mind, how many signals are expected in the 13C NMR for the following compounds?




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Common 13C NMR Shifts




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checklist
Mark Yourself Question
  1. Grab a piece of paper and try this problem yourself.
  2. When you're done, check the "I have answered this question" box below.
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checklist
Mark Yourself Question
  1. Grab a piece of paper and try this problem yourself.
  2. When you're done, check the "I have answered this question" box below.
  3. View the solution and report whether you got it right or wrong.



Extra Practice
The 13C NMR spectrum belongs belongs to which of the four molecules?
Assign the 1H and 13C NMR spectra of the following molecule:
How many different 1H and 13C NMR signals would you expect for the following molecules? Include the expected multiplicity and relative integration for the signals in the 1H NMR spectrum
(Duplicated)
The 13C NMR spectrum belongs belongs to which of the four molecules?
The 13C NMR spectrum belongs belongs to which of the four molecules?
Lab techniques: 13C NMR
The 13C NMR spectrum provided belongs to which of the following molecules?
Lab techniques: 13C NMR
The 13C NMR spectrum provided belongs to which of the following molecules?
Example: 13C NMR 1
Example: 13C NMR
Assign the 13C NMR spectrum for 3-methyl-butane-2-one.
How many different 1H and 13C NMR signals would you expect for the following compounds? Include the expected multiplicity and relative integration for the signals in the 1H NMR spectrum
Example: 13C NMR 1

How many signals would you expect in the 13C NMR spectra of the following compound?
NMR
How many different 1H and 13C NMR signals would you expect for the following compounds? Include the expected multiplicity and relative integration for the signals in the 1H NMR spectrum
Assign the 1H and 13C NMR spectra of the following compound:
Example: 13C NMR 3

Example: 13C NMR 2

The 13C NMR spectrum belongs belongs to which of the four compounds?
(Duplicated)
The 13C NMR spectrum belongs belongs to which of the four compounds?
The 13C NMR spectrum belongs belongs to which of the four compounds?
13C NMR
In the following 13C NMR spectrum, what is the peak at 208 ppm representing? The compound being analyzed is acetone.
Spectroscopy
Analyze the spectroscopic data to properly identify the unknown molecules.