Ketone chemical structure. Image credit: Flickr
Ketone chemical structure. Image credit: Flickr

In organic chemistry, a ketone is an organic compound containing a carbonyl group, which is a carbon and oxygen atom double bonded to each other. The carbon atom is attached to a couple of R groups, which could comprise oxygen, carbon or any other element. In the case of a ketone, it’s two carbons. If one of the two groups has hydrogen, the organic compound would become an aldehyde. Phenylethanone and propanone are examples of simple ketones. A ketone is also different from other carbonyl-comprising functional groups, namely esters, carboxylic acids and amides.

Ketones, like aldehydes, are naturally widespread, such as in plants and animals, typically merging with other types of functional groups. They’re polar since the oxygen atom’s electronegativity is higher than carbon. Therefore, a ketone is electrophilic (attracts electrons) at carbon and nucleophilic (donates electrons) at oxygen. A ketone is also more water-soluble than similar compounds, thanks to their bonding with hydrogen when introduced to water. Hydrogen bonding increases the attraction between water and solute (dissolved substance).

Making a Ketone

Similar to aldehydes, ketones could be prepared in several ways – in both industrial and academic laboratory setups. A ketone can be acquired as a product courtesy several chemical reactions – such as secondary alcohol oxidization, alkyne hydration, alkene ozonolysis, Friedel-Crafts acylation, using lithium dialkylcuprates, etc. A ketone that comprises alkyne and alkene units are usually referred to as unsaturated ketones. In industries, ketones (such as methylethyl ketone, acetone, and cyclohexanone) are made on a large scale as solvents, pharmaceuticals, and prepolymers.

To convert secondary alcohol to ketone, strong oxidizing agents such as chromic acid and potassium dichromate are needed because oxidizing ketone further takes some serious effort. Adding water to alkyne results in unstable vinyl alcohol, which goes through keto-enol tautomerism (chemical equilibrium between alcohol and aldehyde or ketone) for forming ketones. Adding lithium dialkylcuprate to acyl chloride at reduced temperatures makes a ketone. Hydrolysis of salt created by letting Grignard reagent (chemical reaction) react with nitrile results in good ketone yields.