Infra Red Spectrum - 2

Infrared spectrum 2: propanone, CH₃COCH₃Propanone is a ketone. Its functional group is the C=O (carbonyl) group, bonded to two carbon atoms.Key absorptions• A strong, sharp absorption at about 1715 cm^-1. This is the C=O stretch. The C=O bond is very polar, so it absorbs strongly, and it is usually the deepest trough in the spectrum. Ketones absorb in the range 1700 to 1720 cm^-1.• C-H absorptions at about 2900 to 3000 cm^-1 from the two CH₃ groups.• Several absorptions in the fingerprint region, below 1500 cm^-1.What is missingThere is no broad absorption around 3200 to 3550 cm^-1, so there is no O-H bond. This rules out an alcohol. There is also no very broad absorption from 2500 to 3300 cm^-1, which rules out a carboxylic acid.ConclusionA strong C=O absorption at about 1715 cm^-1 with no O-H absorption shows a compound containing a carbonyl group, such as a ketone. Other ketones, such as butanone, CH₃COCH₂CH₃, also absorb strongly at about 1715 cm^-1, so the molecular formula or a mass spectrum is needed to say which ketone is present.Link to oxidation: propanone is made by oxidising propan-2-ol, so this spectrum is what the product of that reaction should look like.