Spectroscopic analysis

You may be asked in practical assessment or in exams to analyze some spectroscopic data and identify an unknown compound. The data may be presented to you as real spectra or the key data may have been extracted and presented in writing.

The trick is to extract little clues from each spectrum. You should eventually come up with only one molecule which fits all the clues. You may also be provide with some results of simple chemical tests which should provide further confirmation of your final solution.

Spectral analysis can be quite fun if you like puzzles. You can find out using the following examples. Start by looking at the mass spectrum and find the molecular mass from the parent ion. Then take a look at the top end of the infra-red spectrum and try to spot any functional groups .

Now take a look at the nmr spectrum. How many hydrogen atoms are present? How many different environments are there? Are the earlier functional groups confirmed? You should now be able to put all this information together to come up with a suggested structure for the unknown molecule. Check through each of the spectra. Does your suggested structure fit with all the facts? See if you can find the expected fragments on the mass spectrum. If you have been given the results of any chemical tests these should also fit in with your proposed functional group(s).