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[0097] 74 g (1 mol) propionic acid is placed in a 250 ml three neck flask at room temperature under nitrogen. First 61 g (0.62 mol) concentrated sulfuric acid and then 68 g of a 50 wt.-% hydrogen peroxide solution (1 mol H$_{2}$0 2 and 1.88 mol water) are added to the solution within 10 minutes with external cooling. The molar quotient of H$_{2}$ O$_{2}$:propionic acid:H SO$_{4 }$ of the starting solution is 1:1:0.62 at this sto› ichiom2etry. External cooling with an ice bath ensures that the reaction temperature does not exceed 20° C. and stirring continues for a further 30 minutes. The solution thus obtained is extracted with lx80 g and 3x30 g toluene. The extracted toluenic phase is dried with MgSO $_{4}$ , a clear toluenic phase being obtained after filtration which contains perpropionic acid (19.2 wt.-%), propionic acid (9.1 wt.-%), hydrogen peroxide (0.16 wt.-%) and water (0.25 wt.-%). 

[0098] The toluenic solution of perpropinic acid (0.445 mol) is transferred to a 500 ml three neck flask fitted with an internal thermometer, dropping funnel and gas bubble counter. 49.2 g ~-IP (GC content: 97.4%; 0.356 mol) is dropped in within 15 minutes under nitrogen, while keeping the internal temperature of the solution at 30° C. (~-IP/ peracid=0.8 1). Stirring is continued for a further 100 min› utes at 30° C. and the course of the reaction is monitored by GC. After 105 minutes the reaction is terminated and the toluenic product solution is cooled to room temperature and washed with a little 10 wt.-% aqueous NaHSO$_{3 }$ solution. After drying with MgSO$_{4 }$ the solution was filtered. 

[0099] The toluenic solution of ~-IPO/HIP (0.35 mol) and 0.33 g (0.5 mol%) MgBr$_{2 }$ were placed at room temperature, under nitrogen, in a three neck flask fitted with an internal thermometer, Liebig cooler and mechanical stirrer. The solution is heated for 30 minutes to 80° C. The results of GC quantification of the product solution are as follows: 

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[0100] Further variations and modifications of the forego› ing will be apparent to those skilled in the art and are intended to be encompassed by the claims appended hereto. 

[0101] German priority application 100 24 264.2 is relied on and incorporated herein by reference. 

We claim: 

1. A process for the production of dihydroketoisophorone (2,2,6-trimethylcyclohexane-l,4-dione) represented by the structure 

## Production of DH-KIP from ~-IP 

## EXAMPLE 23 

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comprising reacting ~-isophorone (3,5,5-trimethylcyclohex- 3-en-1-one) represented by the structure 

with an organic percarboxylic acid in the form of its non› aqueous solution in an inert organic solvent at a temperature of 0° C. to 300° C., the percarboxylic acid used as oxidizing agent being formed in a pre-determined equilibrium and absorbed or extracted with the solvent used for oxidation, thereby forming: 

a mixture of ~-isophorone epoxide 

and its isomer 4-hydroxyisophorone (HIP), 

isomerizing said mixture "in situ" thermally or in the presence of an acid catalyst or in the presence of a salt. 

2. The process according to claim 1, wherein isomerizing said mixture of ~-IPO and HIP obtained as an intermediate is carried out in an organic solvent, which was also used for extraction of the organic percarboxylic acid. 

3. The process according to claim 1, wherein the percar› boxylic acid used an oxidizing agent is formed in a pre› determined equilibrium reaction from the corresponding carboxylic acid, an aqueous hydrogen peroxide solution and sulfuric acid and absorbed and extracted with the solvent used for oxidation and isomerization. 

4. The process according to claim 1, wherein the isomer› izing is carried out thermally in a temperature range of 20° C. to 200° C. 

5. The process according to claim 1, wherein a member selected from the group consisting of an alkali- or earth alkali halogenide, halogenides of groups IB, IIB and VIIIB and corresponding Lewis acids is used as a reaction catalyst. 

6. The process according to claim 1, wherein a protonic acid with a pKA<3 is said acid catalyst for isomerization. 

7. The process according to claim 1, wherein the mixture obtained as an intermediate is isomerized in the presence of a solid, acid or super acid catalyst and the reaction proceeds as a solid/liquid two-phase process. 

8. The process according to claim 1, wherein the isomer› izing is catalyzed by a carboxylic acid formed from reduc› tion of percarboxylic acid. 

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