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 A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

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 Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%� ...

affords the oxide. Isophorone is degraded by attack of hydroxyl radicals.

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. Available forms of isophorone after a light dependent reaction

Available forms of isophorone after a light dependent reaction

Natural Occurrence

Isophorone occurs naturally in

cranberries Cranberries are a group of evergreen dwarf shrubs or trailing vines in the subgenus ''Oxycoccus'' of the genus ''Vaccinium''. In Britain, cranberry may refer to the native species ''Vaccinium oxycoccos'', while in North America, cranberry m ...

Synthesis

Isophorone is produced on a multi-thousand ton scale by the aldol condensation of

acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscib ...

using KOH. Diacetone alcohol, mesityl oxide, and 3-hydroxy-3,5,5-trimethylcyclohexan-1-one are intermediates. A side product is

beta-isophorone β-Isophorone is an organic compound with the formula (CH3)3C6H7O. Classified as a β,γ-unsaturated ketone, it is an isomer of and common impurity in the major industrial intermediate α-isophorone, which is produced from acetone. Like the alph ...

, where the C=C group is not conjugated with the ketone. Synthesis of Isophorone using a self-condensation reaction

Applications

The partly hydrogenated derivative trimethylcyclohexanone is used in production of

polycarbonate Polycarbonates (PC) are a group of thermoplastic polymers containing carbonate groups in their chemical structures. Polycarbonates used in engineering are strong, tough materials, and some grades are optically transparent. They are easily work ...

s. It condenses with phenol to give an analogue of

bisphenol A Bisphenol A (BPA) is a chemical compound primarily used in the manufacturing of various plastics. It is a colourless solid which is soluble in most common organic solvents, but has very poor solubility in water. BPA is produced on an industrial s ...

. Polycarbonates produced by phosgenation of these two diols produces a polymer with improved thermal stability. Trimethyl

adipic acid Adipic acid or hexanedioic acid is the organic compound with the formula (CH2)4(COOH)2. From an industrial perspective, it is the most important dicarboxylic acid: about 2.5 billion kilograms of this white crystalline powder are produced annually, ...

and 2,2,4-trimethylhexamethylenediamine are produced from trimethylcyclohexanone and trimethylcyclohexanol. They are used to make specialty

polyamide A polyamide is a polymer with repeating units linked by amide bonds. Polyamides occur both naturally and artificially. Examples of naturally occurring polyamides are proteins, such as wool and silk. Artificially made polyamides can be made through ...

s. Hydrocyanation gives the nitrile followed by reductive amination gives

isophorone diamine Isophorone diamine (usually shortened to IPDA) is a diamine with the formula (CH3)3C6H7(NH2)(CH2NH2). It is a colorless liquid. It is a precursor to polymers and coatings. Production It is usually produced as a mixture of the ''cis''- and ''tra ...

. This diamine is used to produce

isophorone diisocyanate Isophorone diisocyanate (IPDI) is an organic compound in the class known as isocyanates. More specifically, it is an aliphatic diisocyanate. It is produced in relatively small quantities, accounting for (with hexamethylene diisocyanate) only 3.4% ...

which has certain niche applications. Full hydrogenation gives

3,3,5-Trimethylcyclohexanol 3,3,5-Trimethylcyclohexanol is a precursor to the vasodilator cyclandelate, the sunscreen component homosalate and the VP nerve agent. It can be synthesized by hydrogenation of isophorone. It has a mint flavour. See also *Cyclandelate *VP (nerve ...

, a precursor to both sunscreens and chemical weapons.

Safety

The LD50 value of isophorone in rats and rabbits by oral exposure is around the 2.00 g/kg. The safety aspects of isophorone have been subject to several studies.{{Cite journal, last=W. Morton Grant, Joel S. Schuman M.D, date=11 February 2016, title=Toxicology of the Eye: Effects on the Eyes and Visual System from Chemicals, Drugs, Metals and Minerals, Plants, Toxins, and Venoms; Also, Systemic Side Effects from Eye, journal=Med (2-Volume Set) 4th Edition, Page 863

History

The use of isophorone as a solvent resulted from the search for ways to dispose of or recycle

, which is a waste product of

phenol Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it req ...

synthesis by the Hock method.Isophorone history at Degussa
/ref>

References

Enones Ketone solvents Cyclohexenes