baeyer-villager question

[n00dle]

In bio's post about baeyer-villager oxidation, specifically:

3) Baeyer-Villiger Oxidation....... To a 6 liter FB flask on the mag stirrer hotplate in a water bath was added 2.3L Glacial Acetic Acid (RA) 615g NaPerborate 4H2O and 430g MePhBuO with stirring. This starts endothermic and mag stirring is inadequate until heat is added and the stuff dissolves. Added the crystals over ca. 1/2 hour while heating to about 45 deg. After the induction period added ice and or heating periodically to keep the solution temp 55-65 deg.  Can get into this more later if anyone actually is ready to do it. Stir vigorously keeping the temp as above for 6 hours. If it gets hotter as long as controllable it's OK. Be very carefull here I already had a near runaway........ Proceed slowly and carefully........ Cool to ambient then either dilute with water or recover the NaBO2 and acid first. Now extract with toluene or DCM. I used DCM this time and wish I didn't. Anyway extracted with 1.2L DCM washed with water and brine then removed solvent to leave the enol ester.

SWIM is wondering about "Cool to ambient then either dilute with water or recover the NaBO2 and acid first." One would think the vast amount of GAA used that one would not like to add water converting it to non-GAA. Can the acetic acid be reclaimed as GAA if one adds the perborate/butanone, performs the reaction, distills the GAA away, and then washes with water? Can this GAA be used again? There might be residual perborate as suggested but I guess this would just be used in the next oxidation. Basically SWIM is trying to find a way to reuse the GAA for more oxidations. Or does SWIM have to add the water extract the propanone then convert the AA to GAA via distillation with H2SO4?

[Rhodium]

First of all, the acetic acid solvent is no longer anhydrous after the reaction, as the NaBO₃·4H₂O is ~40% water by weight, so you have at least 10% water in the acetic acid.

If you want to reclaim this 90% acid, I suggest that you distill off around 2000 mL of it under vacuum (as boiling the reaction mixture in 114°C acetic acid might lower yields), then dilute the residue with water and extract as in the writeup. The 90% acetic acid reclaimed will have to be dried before it is reused in the next run, and I'm not sure how successful the distillation from sulfuric acid has been proven to be, but the results are available in TFSE.

As hydrolysis of the P2P enol formate produced in the baeyer-villiger oxidation will give rise to formic acid, any acetic acid distilled off will contain formic acid as well, and this acid will decompose to carbon monoxide if distilled from sulfuric acid, so watch out for that happening.

[n00dle]

well in that case could one just stick thier ketone solvent in without adding the extra liter of water? extract the ketone first, then deal with the AA later? SWIM just doesnt see why they add more water. to change PH?

[Rhodium]

You cannot extract an acetic acid solution of organics effectively without diluting with quite some water. A lot of acid would dissolve in the extraction solvent instead of staying behind, and a lot of product would stay behind in the acid. Or, depending on extraction solvent, you wouldn't even get two layers...