|Jmol-3D images||Image 1
|Molar mass||72.11 g mol−1|
|Melting point||−86 °C (−123 °F; 187 K)|
|Boiling point||79.64 °C (175.35 °F; 352.79 K)|
|Solubility in water||27.5 g/100 mL|
|Refractive index (nD)||1.37880|
|Dipole moment||2.76 D|
|EU classification||Flammable (F)
|R-phrases||R11 R36 R66 R67|
|S-phrases||(S2) S9 S16|
|Flash point||−9 °C (16 °F; 264 K)|
|LD50||6.86 mL/kg (oral, rat)|
|Related Ketones||Acetone; 3-pentanone; 3-Methylbutanone|
|Supplementary data page|
|n, εr, etc.|
Solid, liquid, gas
|Spectral data||UV, IR, NMR, MS|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
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.
- CH3CH(OH)CH2CH3 → CH3C(O)CH2CH3 + H2
In this way, approximately 700M kg are produced yearly. Other routes that have been examined but not implemented include Wacker oxidation of 2-butene and oxidation of isobutylbenzene (analogous to the industrial route to acetone).
As a solvent
Butanone is an effective and common solvent and is used in processes involving gums, resins, cellulose acetate and nitrocellulose coatings and in vinyl films. For this reason it finds use in the manufacture of plastics, textiles, in the production of paraffin wax, and in household products such as lacquer, varnishes, paint remover, a denaturing agent for denatured alcohol, glues, and as a cleaning agent. It has similar solvent properties to acetone but boils at a higher temperature and has a significantly slower evaporation rate. Butanone is also used in dry erase markers as the solvent of the erasable dye.
As a plastic welding agent
As butanone dissolves polystyrene, it is sold as "model cement" for use in connecting together parts of scale model kits. Though often considered an adhesive, it is actually functioning as a welding agent in this context.
This chemical must be handled carefully.
Butanone can react with most oxidizing materials, and can produce fires. It is moderately explosive; it requires only a small flame or spark to cause a vigorous reaction. Butanone fires should be extinguished with carbon dioxide, dry chemicals or alcohol foam. Concentrations in the air high enough to be flammable are also intolerable to humans due to the irritating nature of the vapour.
Butanone is an irritant, causing irritation to the eyes and nose of humans, but serious health effects in animals have been seen only at very high levels. When inhaled, these effects included birth defects in mice, but only at the highest dose tested (3000 ppm for 7 hours/day).
In 2005, the U. S. Environmental Protection Agency removed butanone from the list of hazardous air pollutants (HAPs). After technical review and consideration of public comments, EPA concluded that potential exposures to butanone emitted from industrial processes may not reasonably be anticipated to cause human health or environmental problems. However, some reviewers have advised caution in using methylethyl ketone because of reports of neuropsychological effects. 
Butanone is listed as a Table II precursor under the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances.
- Merck Index, 11th Edition, 5991.
- Wilhelm Neier, Guenter Strehlke "2-Butanone" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002.
- Turner, Charles F.; McCreery, Joseph W. (1981). The Chemistry of Fire and Hazardous Materials. Boston, Massachusetts: Allyn and Bacon, Inc. p. 118. ISBN 0-205-06912-6.
- Ashford's Dictionary of Industrial Chemicals, Third edition, 2011, ISBN 978-0-9522674-3-0, pages 6013-4
- Apps, E. A. (1958). Printing Ink Technology. London: Leonard Hill [Books] Limited. p. 101.
- Fairhall, Lawrence T. (1957). Industrial Toxicology. Baltimore: The Williams and Wilkins Company. pp. 172–173.
- Schwetz et al. (1991). "Developmental toxicity of inhaled methyl ethyl ketone in Swiss mice". Fund. Appl. Toxicol. 16 (4): 742–748. doi:10.1016/0272-0590(91)90160-6.
- Thompson, S.B.N. “Implications for cognitive rehabilitation and brain injury from exposure to Methyl Ethyl Ketone (MEK): a review.” Journal of Cognitive Rehabilitation 2010; 28(Winter): 4-14. doi: jofcr.com/vol284/v28i4thompson.pdf.
- List of Precursors and Chemicals Frequently Used in the Illicit Manufacture of Narcotic Drugs and Psychotropic Substances Under International Control, International Narcotics Control Board