We are busy in oxidation of a long chain aliphatic alcohol to acid by H2O2 with catalytic quantity of Na2WO4. 2H2O and PTC (Tricaprylmethylammonium chloride), but we could not see exothermicity during addition of H2O2 for 2/3 reactions, and getting less yield compare to our previous reactions. Does anyone have experiences of catalyst inactivation during the course of this type of oxidation reaction?
H2O2 reacts with Na2WO4 to produce "law molecular weight polyperoxotungstates," which are likely to be the reactive species. pH is a key parameter, which controls overall process. If you are running the reaction in organic solvent, then the solvent nature is important. If H2O2 solution in water and the solvent are not miscible, you have two phases reaction. Thus, numerous parameters may control your reaction.
Try to acidify reaction mixture stepwise with H3PO4. Heteropolyacids or its monobasic salt form more powerful oxidant with H2O2 and are more extractable into organic phase.
The best pH is in the range of 0.3-4 which is suitable to form peroxotungstate species. High temperature lead to decomposition of H2O2 and thus reduce the efficiency. If your H2O2 is not fresh (I mean the bottle has been opened for a long time) use titration to determine the accurate amounts of H2O2. Be aware that you have two oxidation steps and thus need at least 2 eq. of oxidant.
- Badges
- Science topic
- Similar topics
- Chemistry