10  US 2002/0165414 Al  Nov. 7, 2002  EXAMPLE 23  Production of DH-KIP from ~-IP  [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:  [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  0  0  Converted 13-IPO:  Yield DH-KIP:  Selectivity (HIP+ DH-KIP)  100%  97%  98%  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.  0  OH  0  0  0 