A Ketone ( derived from the German word for Acetone – Aketon) is a class of organic compounds, such as acetone, having a carbonyl group (C=O) linked to a carbon atom in each of two hydrocarbon radicals and having the general formula R(CO)R’, where R may be the same as R’ in hydrocarbon ( alkyl or aryl) groups.
The ketones acetone and methyl ethyl ketone are used as solvents due to their low molecular weight. They are prepared by oxidation of secondary alcohols or the destructive distillation of salts of organic acids. Ketones are important intermediates in the syntheses of organic compounds and are related to aldehydes but less active.
Ketones are colorless liquids and because of these characteristic are used in flavoring and the perfune industry.Ketones such as methyl ethyl ketone and acetone are miscible with water. The Water solubility of Ketones with higher homologs reduce with an increase in carbon atoms.
Methyl ketones are more reactive than the higher ketones because of steric group effects.
Different methods exist in the production of ketones. One of the most important methods is hydrocarbon oxidation with air. Aerobic oxidation of cyclohexane produces cyclohexanone while acetone is produced by cumene air-oxidation.
Oxidation of secondary alcohols is often used to prepare small scale organic synthetic applications.
R2CH(OH) + O → R2C=O + H2O
Potassium permanganate is used as strong oxidants for the above reaction while Dess-Martin periodinane or the Moffatt-Swern is used for milder conditions.
Gem halide hydrolysis can be used to prepare ketones. Subsequent enol-keto tautomerization of alkynes can produce ketones also. The Friedel-Crafts reaction and the Fries rearrangement can also produce aromatic ketones while cyclic ketones can be prepared using the Ruzicka cyclization of dicarboxylic acids.
Storage and Handling
Ketones are usually stored in carbon steel tanks. Stability of the product is achieved if inorganic zinc silicate coating is used in tanks when there is possible long-tern storage planned.
Dessicant units can be installed in the storage tank’s vent line to dry incoming air. Compatibility between the dessicant and ketone vapors should be considered.
Common ketones such as acetone, 2-butanone, and carvone have different uses. Acetone is commonly used as a fingernail polish remover and as lacquer and varnish solvents. It is very flammable and is used as a cleaning fluid. Chloroform, ketone, and a number of other compounds use acetone for their preparation. The manufacture of smokeless powders cordite and celluloid also utilize acetone.
2-butanone is used commonly as solvent and strips paint.
Spearmint flavoring is the use of carvone.