|Preferred IUPAC name
|3D model (Jmol)||Interactive image
|Molar mass||72.11 g·mol−1|
|Odor||mint or acetone-like|
|Melting point||−86 °C (−123 °F; 187 K)|
|Boiling point||79.64 °C (175.35 °F; 352.79 K)|
|27.5 g/100 mL|
|Vapor pressure||78 mmHg (20°C)|
Refractive index (nD)
|Safety data sheet||See: data page|
EU classification (DSD)
|R-phrases||R11 R36 R66 R67|
|S-phrases||(S2) S9 S16|
|Flash point||−9 °C (16 °F; 264 K)|
|505 °C (941 °F; 778 K)|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|2737 mg/kg (oral, rat)
4050 mg/kg (oral, mouse)
LC50 (median concentration)
|12667 ppm (mammal)
13333 ppm (mouse, 2 hr)
7833 ppm (rat, 8 hr)
|US health exposure limits (NIOSH):|
|TWA 200 ppm (590 mg/m3)|
|TWA 200 ppm (590 mg/m3) ST 300 ppm (885 mg/m3)|
IDLH (Immediate danger)
|Acetone; 3-pentanone; 3-Methylbutanone|
|Supplementary data page|
|Refractive index (n),
Dielectric constant (εr), etc.
|UV, IR, NMR, MS|
Except where otherwise noted, 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 (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
This is used to produce approximately 700 million kilograms yearly. Other syntheses that have been examined but not implemented include Wacker oxidation of 2-butene and oxidation of isobutylbenzene, which is analogous to the industrial production of 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 and many other plastics, it is sold as "model cement" for use in connecting parts of scale model kits. Though often considered an adhesive, it is actually functioning as a welding agent in this context.
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 agents, or alcohol-resistant foam. Concentrations in the air high enough to be flammable are intolerable to humans due to the irritating nature of the vapor.
Butanone is an irritant, causing irritation to the eyes and nose of humans. Serious health effects in animals have been seen only at very high levels. These included skeletal birth defects and low birth weight in mice, when they inhaled it at the highest dose tested (3000 ppm for 7 hours/day). There are no long-term studies with animals breathing or drinking it, and no studies for carcinogenicity in animals breathing or drinking it.:96 There is some evidence that methyl ethyl ketone can potentiate the toxicity of other solvents, in contrast to the calculation of mixed solvent exposures by simple addition of exposures. As of 2010[update], some reviewers 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.
Emission of butanone was regulated in the US as a hazardous air pollutant, because it is a volatile organic compound contributing to the formation of tropospheric (ground-level) ozone. In 2005, the U. S. Environmental Protection Agency removed butanone from the list of hazardous air pollutants (HAPs). 
- Merck Index, 11th Edition, 5991.
- Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 725. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
- "NIOSH Pocket Guide to Chemical Hazards #0069". National Institute for Occupational Safety and Health (NIOSH).
- "2-Butanone". Immediately Dangerous to Life and Health. National Institute for Occupational Safety and Health (NIOSH).
- 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.
- "Methyl ethyl ketone (MEK) (CASRN 78-93-3)". Integrated Risk Information System (IRIS). EPA. 26 September 2003. Retrieved 16 March 2015.
- "U.S.Toxicological review of Methyl ethyl ketone In Support of Summary Information on the Integrated Risk Information System (IRIS)" (PDF). U.S. Environmental Protection Agency. September 2003. p. 152. Retrieved 16 March 2015.
- F D Dick. Solvent neurotoxicity, Occup Environ Med. 2006 Mar; 63(3): 221–226. doi: 10.1136/oem.2005.022400, PMCID: PMC2078137
- 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 Archived February 27, 2008, at the Wayback Machine., International Narcotics Control Board
- Federal Register Volume 70, Issue 242 (December 19, 2005)
- Barbara Kanegsberg (n.d.). "MEK No Longer a HAP". Bfksolutions newsletter. Archived from the original on 2 April 2015. Retrieved 2 April 2015. 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.
- "EPA De-Lists MEK from CAA HAP List". www.pcimag.com. Retrieved 2016-07-30.