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