1H NMR Spectroscopy for CHM 222L Professor: S. Bruce King | Programming & Design: Yue-Ling Wong

Topics >>>
  NMR Intro
No. of Diff. Hydrogens
  Chemical Shift
  Web Resources

Practice >>>
Predict Spectrum I:

Predict Spectrum II:

Peak Assignments:

quick review

Number of Different Hydrogens

Ethyl acetate contains 8 hydrogens and some of them are different from each other.
For example, those labeled A are attached to a carbon bonded to a carbonyl group and are different from the hydrogens labeled B which are bonded to a carbon attached to an oxygen atom.

You can check whether certain hydrogens are the same or equivalent by replacing each hydrogen with some group X and seeing if you generate the same compound. You should convince yourself that replacing each hydrogen labeled A by X gives you identical compounds which are all equivalent by a C-C bond rotation. If this is difficult to "see" look at this molecular model of ethyl acetate to see if you can convince yourself that all the hydrogens labeled A are the same.
(Requires Chime plugin)
Drag to rotate the molecular structure above. To start animation, right-click on the above molecular model and select Animation, Start.

Highlight one of the A-labeled hydrogen
Highlight one of the C-labeled hydrogen

Finally, every chemically distinct hydrogen or group of hydrogens will give a resonance in the NMR spectra.

Review Questions

For ethyl acetate

1. Are all the hydrogens labeled A the same?
Yes No
2. Are all the hydrogens labeled B the same?
Yes No
3. Are all the hydrogens labeled C the same?
Yes No
4. How many different types of hydrogens does this molecule have?
5. How many NMR resonances will this molecule have?