Ketone

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Ketones are organic compounds having at least one RC(=O)R' group, where R and R' can be a variety of carbon-containing substituents, like alkanes, alkenes, alkynes, or aromatics. Compounds with non-carbon substituents like H, OH, NH2 or halogens are not ketones, but aldehydes, carboxylic acids, amides or acyl halides respectively.

Properties

Ketones are colorless liquids, with a mildly pleasant odor. Of all ketones, only acetone is miscible with water, while the rest are soluble or miscible with various organic solvents.

Preparation

Aldehydes can be easily prepared through the Jones oxidation of secondary alcohols, using chromium trioxide or potassium dichromate dissolved in dilute sulfuric acid. Potassium permanganate can also be used.

A more convenient route involves the pyrolysis of carboxylic acid salts, process known as ketonic decarboxylation. A few examples below:

2 CH3COONa → (CH3)2CO + Na2CO3
CH3COONa + CH3CH2COONa → (CH3)CO(CH3CH2) + Na2CO3
CH3COONa + C6H5COONa → (CH3)CO(C6H5) + Na2CO3

Other synthesis routes are hydration of alkynes, reaction of Grignard reagents with nitriles, followed by hydrolysis, decarboxylation of carboxylic anhydrides, oxidation of amines with iron(III) chloride, Friedel–Crafts acylation, etc.

Safety

Unlike aldehydes, ketones have low toxicity and low carcinogenic potential. They are however very flammable.

References

Relevant Sciencemadness threads