Butanone, also known as methyl ethyl ketone or MEK, is an organic compound with the formula CH3C(O)CH2CH3. This colorless liquid ketone has a sharp, sweet odor reminiscent of butterscotch and acetone. It is produced industrially on a large scale, and also occurs in trace amounts in nature. It is soluble in water and is commonly used as an industrial solvent
Example
C4H8OMW 72
First calculate the degree of unsaturation: the answer is 1. This means that the compound has four carbons and an oxygen, it can have a carbon-carbon double bond, a carbon-oxygen double bond - a carbonyl, or a ring.
IR Spectrum
A table of characteristic IR absorptions is available online: click on the link below. Note that this chart is also linked to in the frame to the left.The IR spectrum for Example 1 is below. Since the degree of unsaturation indicates that the compound could have a carbonyl, let's look for that first, since carbonyl bands are strong and distinct. Carbonyls show up in the region 1760-1665, and specifically, saturated aliphatic ketone close to 1715. Sure enough, there is a band at 1718 indicating a saturated aliphatic ketone.
Think of possible structures
Now we know that the compound has a carbon-oxygen double bond, but there are still a few ways that this four-carbon molecule could be put together. Examples are below:Proton NMR Spectrum
A table of characteristic NMR shifts is available online: click on the link below. Note that this chart is also linked to in the frame to the left.- Before you look at the NMR spectrum, think about what the spectrum of 2-butanone should look like. There are three different types of protons:
Summary
Example 1 is 2-butanone:
COSY