4-Methyl-2-pentanone [108-10-1], methyl isobutyl ketone, MIBK, CH3COCH2CH(CH3)2, C6H12O, Mr 100.16. 4-Methyl-2-pentanone is a colorless liquid with a less pronounced ketone-like odor. 4-Methyl-2-pentanone is poorly soluble in water but is miscible with common organic solvents. It forms an azeotrope with water and with a large number of solvents. For example, the azeotrope with water (bp 87.9℃) contains 75.7 wt % 4-methyl-2-pentanone, and that with n-butanol (bp 114.4℃) 70 wt % 4-methyl-2- pentanone.

Uses

The major application of 4-methyl-2- pentanone is as a solvent for vinyl, epoxy, and acrylic resins, for natural resins, and for nitrocellulose. A further use is as a solvent for dyes in the printing industry. 4-Methyl-2-pentanone is also a versatile extracting agent, e.g., for the production of antibiotics, or the removal of paraffins from mineral oil for the production of lubricating oils. The importance of 4-methyl-2-pentanone as an intermediate for synthesis is relatively low. The most important product is 4-methyl-2-pentanol, obtained by hydrogenation of the ketone. 4- Methyl-2-pentanone peroxide has some importance as a polymerization initiator for ethylene and for the hardening of unsaturated polyester resins.

Production

4-Methyl-2-pentanone can be produced industrially from acetone or isopropyl alcohol according to the following four processes:
1. In three steps from acetone via diacetone alcohol and mesityl oxide, with subsequent hydrogenation.

2. In two steps from acetone via mesityl oxide. 

3. In one step from acetone and hydrogen. 

4. As a byproduct in the dehydrogenation of isopropyl alcohol to acetone.