I am comparing two IR spectrums of the same molecule, one in the solid state and one in $\ce{CH2Cl2}$ solution. There is only one CO group in the molecule.

Why does the solid state spectrum show two carbonyl stretches, while the solution spectrum has only one carbonyl stretch?

  • 3
    $\begingroup$ Please provide more information about your molecule and the spectra, and the preparation of samples. In its current state the question is very vague and broad. $\endgroup$ – Martin - マーチン May 18 '17 at 6:27
  • $\begingroup$ In solution, the material to be characterised experiences a different environment than in its own matrix. In extremis there is nujol as apolar matrix, and KCl as salty matrix, for example. In the pure solid state, the accessibility of vibrational states may be a different one, in particular in the crystalline state where special sites and their local symmetry may allow / disallow vibrations to occur (in case of perovskites, for example). $\endgroup$ – Buttonwood May 19 '17 at 20:28

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