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All 3 posts Subject: Sulfuric Acid as Peracid Catalyst Please login to post Down

bio
(Hive Bee)
09-27-04 22:57
No 533461
      Sulfuric Acid as Peracid Catalyst

The following table (from the Percarbonate/Perborate review on Rhodiums site) is the percentage of Available Oxygen present as "peracid type" as determined by titration after NaPerborate/carboxylic acid (1:10 molar)mixing at 40deg.

   ACID .5hr 1hr    2hr    3hr

   Formic >90% >90    >90    >90
   Acetic    20 46 66 73
   Propionic    2    9 19 31
   Acetic + 1% H2SO4 56 72 78 80

Since the perborate is mostly consumed in about an hour at 70deg (in my experience) it can be easily seen that the peracid formation should be essentially complete within about 2 hours for maximum yield in the Baeyer/Villiger oxidation of unsaturated ketones. In fact in the reaction I am referring to the bulk of the O2 is released in only about 30-45min although it continues slowly for another 2 or 3 hours depending on the temperature.

My question is; does the 1% Sulfuric Acid amount (no examples are given) mean 1 mole percent, which would be 100mm or about 9.8 grams, or 1% of the weight of acid (about 6g for acetic)????

Rhodium
(Chief Bee)
09-27-04 23:10
No 533462
User Picture       1% H2SO4

I believe they are referring to the proportions given in https://www.rhodium.ws/pdf/peracid.pdf

^{The Hive - Clandestine Chemists Without Borders}

bio
(Hive Bee)
09-28-04 22:59
No 533656
      Peracid Catalysts

Yes, thank you Rhodium.

I recall reading this before when you had posted it in twodogs thread. Very interesting that there is such a huge difference in the time to maximum concentration 80hrs using 30% H2O2 (journal article) versus about 3hours, review article not definite on time to max concemtration. This can't be explained by temperature alone (22 versus 40 deg) and would seem to confirm the reviews statement that something more than just peracid formation is happening (boron species?)

I am preparing to treat the NaPerborate 4H20 with 35% H2O2 per the patent (US2491789) found recently in another thread. These explain that drying the perborate after additional H2O2 treatment has a much greater effect on activity that simple adding more H2O2 to the reaction, which must be the water effect.

If any of you other bees out there with experience in peracid reactions especially catalysed ones would be willing to share your data I would also reciprocate and perhaps not reinvent the wheel again.

What is found in the Journals is not always optimum from the standpoint of simplicity combined with best yields. Apparently Mn Sulfate is a good peracid catalyst ( best of 20 or so tested). Has anyone tried this?

Also I would like to get a discussion going on the "recycling" of the oxidation mixture which according to some patents can bring yields approaching quant if done "appropriatly".

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	All 3 posts		Subject: Sulfuric Acid as Peracid Catalyst		Please login to post		Down


		bio (Hive Bee) 09-27-04 22:57 No 533461				Sulfuric Acid as Peracid Catalyst
						The following table (from the Percarbonate/Perborate review on Rhodiums site) is the percentage of Available Oxygen present as "peracid type" as determined by titration after NaPerborate/carboxylic acid (1:10 molar)mixing at 40deg. ACID .5hr 1hr 2hr 3hr Formic >90% >90 >90 >90 Acetic 20 46 66 73 Propionic 2 9 19 31 Acetic + 1% H2SO4 56 72 78 80 Since the perborate is mostly consumed in about an hour at 70deg (in my experience) it can be easily seen that the peracid formation should be essentially complete within about 2 hours for maximum yield in the Baeyer/Villiger oxidation of unsaturated ketones. In fact in the reaction I am referring to the bulk of the O2 is released in only about 30-45min although it continues slowly for another 2 or 3 hours depending on the temperature. My question is; does the 1% Sulfuric Acid amount (no examples are given) mean 1 mole percent, which would be 100mm or about 9.8 grams, or 1% of the weight of acid (about 6g for acetic)????



		Rhodium (Chief Bee) 09-27-04 23:10 No 533462				1% H2SO4
						I believe they are referring to the proportions given in https://www.rhodium.ws/pdf/peracid.pdf ^{The Hive - Clandestine Chemists Without Borders}



		bio (Hive Bee) 09-28-04 22:59 No 533656				Peracid Catalysts
						Yes, thank you Rhodium. I recall reading this before when you had posted it in twodogs thread. Very interesting that there is such a huge difference in the time to maximum concentration 80hrs using 30% H2O2 (journal article) versus about 3hours, review article not definite on time to max concemtration. This can't be explained by temperature alone (22 versus 40 deg) and would seem to confirm the reviews statement that something more than just peracid formation is happening (boron species?) I am preparing to treat the NaPerborate 4H20 with 35% H2O2 per the patent (US2491789) found recently in another thread. These explain that drying the perborate after additional H2O2 treatment has a much greater effect on activity that simple adding more H2O2 to the reaction, which must be the water effect. If any of you other bees out there with experience in peracid reactions especially catalysed ones would be willing to share your data I would also reciprocate and perhaps not reinvent the wheel again. What is found in the Journals is not always optimum from the standpoint of simplicity combined with best yields. Apparently Mn Sulfate is a good peracid catalyst ( best of 20 or so tested). Has anyone tried this? Also I would like to get a discussion going on the "recycling" of the oxidation mixture which according to some patents can bring yields approaching quant if done "appropriatly".

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