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enter image description hereWhich organic compound's NMR and IR are these? I have figured out that the compound is a 1,4 substituted benzene. And the substituents are probably not -COOH and -OH from the spectroscopy. Kindly help me in figuring the other groups out. (Data available: Melting Point ~ 116 °C, gives sooty flame)

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  • $\begingroup$ @Soumik Das: The presence of two clean doublets in aromatic reagion of NMR would not agree with your suggestion. It may be 4-nitrophenol, which has $113-114$ $\mathrm{^0C}$ melting point. $\endgroup$ – Mathew Mahindaratne Jan 28 '19 at 16:38
  • $\begingroup$ The very strong signal at ~1350 would fit for C-NO2 $\endgroup$ – Waylander Jan 28 '19 at 21:25
  • $\begingroup$ Why is there no C-H stretch band in the IR spectrum near 3000 $\ce{cm^{-1}}$ ? $\endgroup$ – Shoubhik R Maiti Jan 28 '19 at 21:41
  • $\begingroup$ @pas — When you present an NMR spectrum, you absolutely need to also give the nucleus, the frequency and the solvent. Nevertheless, I agree with Mathew on the 4-nitrophenol. The chemical shift of OH group can vary A LOT depending on the solvent, the temperature and the pH which, in turn, depends on the concentration. In this case, p-nitrophenol is acidic, so the more concentrated it is in the NMR tube, the more acidic the pH and the more the signal will move to the left. $\endgroup$ – SteffX Jan 29 '19 at 13:20
  • $\begingroup$ @MathewMahindaratne The signals of 1,4-substituted benzenes form a AA'XX' system; so despite their appearance for this sample and measurement they do not qualify as simple doublets. $\endgroup$ – Buttonwood Jul 21 '19 at 21:36
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The integrals and shifts in the very simple NMR spectrum are a giveaway that this is a simple compound with two different types of aromatic signal, and another non-aromatic signal from a substituent, at a 2:1 peak integral ratio, hence possibly a para-disubstituted benzene ring with one proton in one substituent, none on the other.

The IR spectrum is practically identical to that in the NIST webbook for p-nitrophenol. Some other clues:

  • Oop Signal at $\pu{800 cm^-1}$: para substitution
  • $\pu{1400-1600cm^-1}$: aromatic cc stretch, matches nicely with typical appearance for para substitution
  • No peak at $\pu{1700cm^-1}$: no carbonyl
  • Weak signals at $\pu{3000cm^-1}$: sp2 stretch, no sp3
  • Signals at $\pu{1350 and 1500cm^-1}$ may be nitro

Note this is a little tricky - a search would show some variation in reported spectra.

The melting point also matches reported values.

This is well in agreement with many of the comments under the original post.

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