Isophorone is an α,β-unsaturated cyclic ketone. It is a colorless liquid with a characteristic peppermint-like odor, although commercial samples can appear yellowish. Used as a solvent and as a precursor to polymers, it is produced on a large scale industrially.
Structure and reactivity
Isophorone undergoes reactions characteristic of an α,β-unsaturated ketone. Hydrogenation gives the cyclohexanone derivative. Epoxidation with basic hydrogen peroxide affords the oxide.
Isophorone is degraded by attack of .
Photodimerization
When exposed to sunlight in aqueous solutions, isophorone undergoes 2+2 photocycloaddition to give three isomeric photodimers (Figure). These "diketomers" are cis-syn-cis, head to tail (HT), cys-anti-cys (HT), and head-head (HH). The formation of HH photodimers is favored over HT photodimers with increasing polarity of the medium.
Natural occurrence
Isophorone occurs naturally in
cranberry.
Synthesis
Isophorone is produced on a multi-thousand ton scale by the aldol condensation of
acetone using KOH. Diacetone alcohol,
mesityl oxide, and 3-hydroxy-3,5,5-trimethylcyclohexan-1-one are intermediates. A side product is
Beta-Isophorone, where the C=C group is not conjugated with the ketone.
[
]
Applications
The partly hydrogenated derivative trimethylcyclohexanone is used in production of . It condenses with phenol to give an analogue of bisphenol A. Polycarbonates produced by phosgenation of these two diols produces a polymer with improved thermal stability.[
]
Full hydrogenation gives 3,3,5-Trimethylcyclohexanol, a precursor to both sunscreens and chemical weapons.
Safety
The value of isophorone in rats and rabbits by oral exposure is around 2.00 g/kg.
History
The use of isophorone as a solvent resulted from the search for ways to dispose of or recycle acetone, which is a waste product of phenol synthesis by the Hock method.[ Isophorone history at Degussa]
See also
