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What further information would allow you to make a positive identification of an organic compound from an infrared spectrum?

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    $\begingroup$ I guess I would use NMR. $\endgroup$ – orthocresol Jun 23 '15 at 18:42
  • $\begingroup$ @orthocresol the question, however, asked about IR. Do you have any other ideas? $\endgroup$ – J. Doe Jun 23 '15 at 18:44
  • $\begingroup$ Are you trying to confirm identity or elucidate the structure of a completely unknown compound? $\endgroup$ – jerepierre Jun 23 '15 at 18:48
  • $\begingroup$ @jerepierre confirm identity $\endgroup$ – J. Doe Jun 23 '15 at 18:51
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    $\begingroup$ @J.Doe Then what you need is an IR spectrum of an authentic sample. $\endgroup$ – jerepierre Jun 23 '15 at 21:20
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If you're analyzing an IR spectrum to find out what compound you have, you'll first want to look past the 1500/cm region to see what functional groups you have. For example, a 1700/cm peak will tell you you have a carbonyl, alcohols will have a peak around 3000/cm, etc. From there, pull up spectra of well known compounds with those functional groups, and compare your compound's 1500/cm to 500/cm region to them. This region is called the "fingerprint region" because it's practically unique for all molecules, so if the spectra match there, they're likely the same compound.

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You can compare your IR spactra to a database entry. Usually, the database provides examples of spectra from a high purity sample and that way you can even see how pure your sample is.

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    $\begingroup$ This is better written as a comment $\endgroup$ – user15489 Jun 24 '15 at 3:28
  • $\begingroup$ Welcome to chemistry.SE! If you had any questions about the policies of our community, please ‎visit the help center. As @santiago (subtly?) points out, we expect our answers to be of a higher quality than this. Please be more elaborate. $\endgroup$ – M.A.R. Jun 24 '15 at 7:27

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