Dear Joseph Dubrovkin

In the case of the molecule 37 in your file, bromoacetone, the appearance of two distinct bands in the C=O stretching region can be attributed to the presence of at least two well-characterized conformers.

For more comprehensive information on this topic, I suggest referring to the following article which provides an in-depth experimental and theoretical vibrational study of bromoacetone in various aggregation states:

Article Raman and infrared spectra, conformational stability, barrie...

For hydrogen bonding you need OH or NH groups. The bands are more likely due to structural symmetry or asymmetry. Looking at ref spectra of Acetone (1) the higher band is seen as a shoulder, not easily explained other than small methyl molecules do have prominent normally weak bands (Fermi resonance ?) There is a danger in looking at expanded short areas of spectra without seeing the full spectrum. I would have guessed that the doublet in the diones was due to symmetric and asymmetric stretching of he carbonyls. However a Aldrich reference spectrum of 2,4-pentadione shows a small doublet at 1700cm-1 but the strongest broad band is at 1630 cm-1 and other bands in the 3200- 2000 cm-1 also indicate OH. Other diketones are similar. This implies that the diketones actually have an enol structure. You need to see the full spectra to try to make sense of the published short spectra.