Aug. 19, 2010  6  US 2010/0210871 Al  tuted, straight-chain and branched (C 1  -C 18 )-alkyl radicals,  (C 3 -C 18 )-cycloalkyl radicals, (C 2 -C 26 )-alkenyl radicals hav› ing one or more double bonds, (CcC 10 )-aryl radicals, espe› cially phenyl radicals, (C 1  -C 18 )-alkyl-(C 6 -C 10 )-aryl radicals,  (CcC 10 )-aryl-(C 1 -C 18 )-alkyl radicals,  especially benzyl  radicals, (C 1  -C 18 )-alkyloxy-(C 1 -C 18 )-alkyl radicals, (C 1  - C 18 )-hydroxyalkyl radicals and (C 1  -C 18 )-alkylthio-(C 1  -C 18 )› alkyl radicals.  [0060]  It is further preferred that R  8  and R $^{9 }$are each inde› pendently selected from the group of unsubstituted and  mono- or polysubstituted, branched and straight-chain (C 1  - C 18 )-alkyl radicals, (C 3 -C 18 )-cycloalkyl radicals, (C 2 -C 26 )› alkenyl radicals having one or more double bonds, (C 2 -C 26 )› alkynyl radicals having one or more triple bonds, (CcC 10 )› aryl radicals, especially phenyl radicals, (C 1  -C 18 )-alkyl-(Cc  C 10 )-aryl radicals, (C 6 -C 10 )-aryl-(C 1  -C 18 )-alkyl radicals,  (CcC 10 )-aryl-(C 2 -C 26 )-alkenyl radicals, (C 1 -C 18 )-alkyloxy› (C1-C18)-alkyl radicals, (C 1  -C 18 )-hydroxyalkyl radicals and  (C 1 -C 18 )-alkylthio-(C 1 -C 18 )-alkyl radicals, any substituents  being selected from the group comprising OH, OR 4 ,  NH 2 ,  NHR 4 ,  NR $^{4}$Rs, Cl, Br, I and F, where R 4  and Rs are each  independently selected from the group comprising H, unsub› stituted and mono- or polysubstituted, branched and straight› chain (C 1  -C 18 )-alkyl radicals, (C 3 -C 18 )-cycloalkyl radicals,  (C 2 -C 26 )-alkenyl radicals having one or more double bonds,  (CcC 10 )-aryl radicals, especially phenyl radicals, (C 1  -C 18 )› alkyl-(CcC10)-aryl radicals, (CcC 10 )-aryl-(C 1  -C 18 )-alkyl  radicals, especially benzyl radicals,(C 1  -C 18 )-alkyloxy-(C 1  - C 18 )-alkyl radicals, (C 1  -C 18 )-hydroxyalkyl radicals and (C 1  - C$_{18}$)-alkylthio-(C 1  -C 18 )-alkyl radicals.  [0061]  In a preferred process, the organic acid is selected  from the group of 2-hydroxyisobutyric acid, 2-hydroxy-4- methylthiobutyric acid, lactic acid, glycolic acid, malic acid,  tartaric acid, gluconic acid, glyceric acid.  [0062]  In a further preferred process, the organic acid is a  beta-hydroxycarboxylic acid of the general formula lb  lb  where R  10 , R  11 ,  R  12  and R  13  are each independently selected  from the group comprising H, OH, OR 4 ,  NH 2 , NHR 4 ,  NR $^{4}$Rs,  Cl, Br, I, F, unsubstituted and mono- or polysubstituted,  branched and straight-chain alkyl radicals, cycloalkyl radi› cals, alkenyl radicals having one or more double bonds, alky› nyl radicals having one or more triple bonds, aryl radicals,  alkylaryl radicals, arylalkyl radicals, arylalkenyl radicals,  alkyloxyalkyl radicals, hydroxyalkyl radicals and alkylthio› alkyl radicals, where R 4  and Rs are each independently  selected from the group comprising H, unsubstituted and  mono- or polysubstituted, straight-chain and branched (C 1  - C 18 )-alkyl radicals, (C 3 -C 18 )-cycloalkyl radicals, (C 2 -C 26 )› alkenyl radicals having one or more double bonds, (CcC 10 )› aryl radicals, especially phenyl radicals, (C 1  -C 18 )-alkyl-(Cc  C 10 )-aryl radicals, (CcC 10 )-aryl-(C 1  -C 18 )-alkyl radicals,  especially benzyl radicals, (C 1  -C 18 )-alkyloxy-(C 1  -C 18 )-alkyl  radicals, (C 1  -C 18 )-hydroxyalkyl radicals and (C 1  -C 18 )-alky› lthio-(C1 -C 18 )-alkyl radicals.  [0063]  The organic acid is preferably selected from the  group of 3-hydroxypropionic acid, 3-hydroxybutyric acid,  3-hydroxyvaleric acid, 3-hydroxyhexanoic acid, 3-hydroxy› octanoic 2 0 acid, 3-hydroxyisobutyric acid. Just like 2-hy› droxyisobutyric acid, 3-hydroxyisobutyric acid can likewise  serve as a precursor for methacrylic acid and methacrylic  esters.  [0064]  In a further preferred process, the stripping medium  or entraining gas used is steam, air, gases, preferably natural  gas, methane, oxygen, inert gas, preferably nitrogen, helium,  argon, or mixtures thereof.  [0065]  With regard to the introduction of the stripping  medium or entraining gas, an amount of stripping medium or  entraining gas, based on the aqueous ammonium salt solution  used, between 1 1/kg and 10 000 1/kg, particularly between  10 1/kg and 500 1/kg and very particularly between 20 1/kg  and 100 1/kg is preferred.  [0066]  In further preferred processes, the organic extractant  is selected from the group of straight-chain or branched ali› phatic ketones having 5 to 18 carbon atoms, heterocyclic  ketones having 5 to 18 carbon atoms, straight-chain or  branched aliphatic alcohols having 4 to 18 carbon atoms,  heterocyclic alcohols having 5 to 18 carbon atoms, straight› chain or branched aliphatic alkanes having 5 to 18 carbon  atoms, cycloalkanes having 5 to 14 carbon atoms, straight› chain or branched ethers having 4 to 18 carbon atoms, aro› matics substituted by halogen atoms or hydroxyl groups,  straight-chain or branched alkanes which are substituted by  halogen atoms and have 1 to 18 carbon atoms, cycloalkanes  which are substituted by halogen atoms and have 5 to 14  carbon atoms, preferably isobutyl methyl ketone, isopropyl  methyl ketone, ethyl methyl ketone, butyl methyl ketone,  ethyl propyl ketone, methyl pentyl ketone, ethyl butyl ketone,  dipropyl ketone, hexyl methyl ketone, ethyl pentyl ketone,  heptyl methyl ketone, dibutyl ketone, 2-undecanone, 2-dode› canone, cyclohexanone, cyclopentanone, 1-butanol, 2-bu› tanol, 1-pentanol, 1-hexanol, 2-hexanol, 3-hexanol, 1-hep› tanol,  2-heptanol,  3-heptanol,  1-octanol,  2-octanol,  3-octanol, 4-octanol,  1-nonanol, 2-nonanol, 3-nonanol,  5-nonanol, 1-decanol, 2-decanol, 1-undecanol, 2-undecanol,  1-dodecanol, 2-dodecanol, cyclopentanol, cyclohexanol,  kerosene, petroleum benzine, pentane, hexane, heptane,  octane, nonane, decane, undecane, dodecane, cyclopentane,  cyclohexane, cycloheptane, methyl tert-butyl ether, petro› leum ether, dibutyl ether, diisopropyl ether, dipropyl ether,  diethyl ether, ethyl tert-butyl ether, dipentyl ether, benzene,  toluene,  a-xylene,  m-xylene, p-xylene,  chlorobenzene,  dichloromethane, chloroform, tetrachloromethane or mix› tures thereof.  [0067]  In further preferred processes, the free acid is  obtained from the extractant laden with the extracted acid by  a separation process selected from distillation, rectification,  crystallization, re-extraction, chromatography, adsorption or  membrane processes.  [0068]  One advantage of the process according to the  invention is that of being less expensive, since the expensive  workup and/or disposal of the amounts of salt obtained in  equimolar amounts is eliminated, and another is that the  back-integration of the ammonia released into a production  process and the closed circuit of the extractant causes it to  work in an environmentally friendly and resource-protective  manner.  [0069]  The use of otherwise much-used assistants, for  example sulphuric acid to release the free acid from the  ammonium salt, is eliminated, just like additional reaction  steps associated with high costs, for example the transamina- Rl2 RIO  0  I  I  //  HO-C-C-C  I  I  \  Rl3 RI!  OH 