Cyclohexanone is a cyclic ketone with the molecular formula C6H10O. Its infrared (IR) spectrum exhibits several distinctive features that can be attributed to its functional groups.
The most notable peak in the IR spectrum of cyclohexanone occurs around 1715 cm-1, which corresponds to the carbonyl (C=O) stretching vibration typical of ketones. This peak is strong and sharp due to the presence of the carbonyl group, which is highly polar and causes significant dipole moment changes during vibration.
Additionally, cyclohexanone contains C–H stretching vibrations that appear in the range of 2850 to 2950 cm-1. These peaks are attributed to the aliphatic C–H bonds of the cyclohexane ring.
The bending vibrations related to the C–H bonds can also be observed in the region around 1450 to 1480 cm-1, resulting from the deformation of those C–H bonds.
Furthermore, the presence of any overtones and combination bands may also be seen, though they are typically weaker and may not be very pronounced in the spectrum.
In summary, the distinct peaks of cyclohexanone’s IR spectrum can be rationalized as follows: a sharp carbonyl stretching vibration indicative of the ketone functionality, along with various peaks from the aliphatic C–H stretching and bending modes. This gives chemists a quick way to identify cyclohexanone solely based on its IR absorptions.