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Methyl isobutyl ketone (MIBK, 4-methylpentan-2-one) is an organic compound with the condensed chemical formula (CH3)2CHCH2C(O)CH3. This ketone is a colourless liquid that is used as a solvent for gums, resins, paints, varnishes, lacquers, and nitrocellulose.[2]

Production

At laboratory scale, MIBK can be produced via a three-step process using acetone as the starting material. Self-condensation, a type of aldol reaction, produces diacetone alcohol,[3] which readily dehydrates to give 4-methylpent-3-en-2-one (commonly, mesityl oxide).[4] Mesityl oxide is then hydrogenated to give MIBK.[5]

Synthesis of MIBK from acetone

Industrially, these three steps are combined. Acetone is treated with a strongly acidic, palladium catalyst-doped cation exchange resin under medium pressure of hydrogen.[6] Several million kilograms are produced annually.[5]

Uses

MIBK tank car in Europe.

MIBK is used as a solvent for nitrocellulose, lacquers, and certain polymers and resins.[5]

Precursor to 6PPD

Another major use is as a precursor to N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylene diamine (6PPD), an antiozonant used in tires. 6PPD is prepared by reductive coupling of MIBK with 4-aminodiphenylamine.[7]

Solvent and niche applications

Unlike the other common ketone solvents, acetone and MEK, MIBK has quite low solubility in water, making it useful for liquid-liquid extraction. It has a similar polarity to ethyl acetate, but greater stability towards aqueous acid and base. It can be used to extract gold, silver and other precious metals from cyanide solutions, such as those used in gold mines, to determine the levels of those dissolved metals. Diisobutyl ketone (DIBK), a related lipophilic ketone, is also used for this purpose. Methyl isobutyl ketone is also used as a denaturing agent for denatured alcohol. When mixed with water or isopropyl alcohol MIBK serves as a developer for PMMA electron beam lithography resist. MIBK is used as a solvent for CS in the preparation of the CS spray used currently by American and British police forces.[8][9]

References

  1. ^ a b c d e f NIOSH Pocket Guide to Chemical Hazards. "#0326". National Institute for Occupational Safety and Health (NIOSH).
  2. ^ United States Environmental Protection Agency (September 2016). "Methyl Isobutyl Ketone (Hexone)". Retrieved 2015-12-13.
  3. ^ Conant, J. B.; Tuttle, N. (1921). "Diacetone Alcohol". Organic Syntheses. 1: 45. doi:10.15227/orgsyn.001.0045.
  4. ^ Conant, J. B.; Tuttle, N. (1921). "Mesityl Oxide". Organic Syntheses. 1: 53. doi:10.15227/orgsyn.001.0053.
  5. ^ a b c Stylianos Sifniades, Alan B. Levy, "Acetone" in Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.
  6. ^ Uhde GmbH (2005). "Uhde Technology Profile: MIBK" (PDF). Archived from the original (PDF) on 2013-12-03. Retrieved 18 October 2021.
  7. ^ Hans-Wilhelm Engels et al., "Rubber, 4. Chemicals and Additives" in Ullmann's Encyclopedia of Industrial Chemistry, 2007, Wiley-VCH, Weinheim. doi:10.1002/14356007.a23_365.pub2
  8. ^ Peter J Gray; Stark, MM; Gray, P. J; Jones, G R. N (2000). "Is CS spray dangerous? : CS is a particulate spray, not a gas" (Response to editorial). BMJ. 321 (7252): 26. doi:10.1136/bmj.321.7252.46. PMC 1127688. PMID 10939811.
  9. ^ Roger Eardley-Pryor (2017). "A Tear Gas Tale". Science History Institute. Retrieved 2021-02-22.

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