[discodermolide]

-18-crown-6 solvates the potassium ion in KMnO₄ while the quad. ammo. salt solvates the MnO₄^- anion, basically.

If the crown ether is that expensive, then don't buy it. (My recommendation) Instead, why not make some yourself? You could use Williamsom ether synthesis, though chances are there will be multiple products.

Toxicity can be handled with some antidote (if possible), some PPE, and a fume hood. In factories people carry around hydrofluoric acid while whistling, and people almost never get hurt. Why so afraid of crown ethers?

If he is making tens of tons a month then he is using very large amounts of catalyst, just take it on a weight basis for an estimate: if the cat is 10% then that is 1 ton of 18-crown-6. Not you can't weigh that out in a fume hood. I am not aware of an antidote for 18-C-6. You need a complete body suit to handle this stuff, with separate air supply, so it is not to be trivialised.

[opsomath]

I used water spiked with pyridine. Worst smell ever.

[magician4]

This isn't a lab prep but an intended commercial process  with target volumes of several tens of tons per month of a not-very-high-value product (~$5-7 / kg).

just my 2 cents: with KMnO4 going at ~ 30$ /kg , and the volumes involved, it might be worthwhile to look into some catalyst / air, oxygen system instead....

regards

Ingo

[discodermolide]

Using an air/oxygen mix on this scale may be problematic, you'd have to keep it under the explosion limit and then then reaction may not work due to the dilution with nitrogen.

[curiouscat]

This isn't a lab prep but an intended commercial process  with target volumes of several tens of tons per month of a not-very-high-value product (~$5-7 / kg).

just my 2 cents: with KMnO4 going at ~ 30$ /kg ,

Are you sure it is so expensive? I was expecting (just intuitively) around $5 /kg; bulk grades. I could be wrong. I'll check again.

[magician4]

that would be ballpark bulk prices in Europe, based on 100 kgs  / shipment CF RoAn
If, however, you became a real huge consumer (like: 100 metric tons/year) and if you imported from, let's say India, you'd significantly would reduce prices down to approx. 1500 euro / metric ton  (approx 1 US-$ per pound)

... but: is your production really that huge?


different countries, different connections, different grades, different amounts...

regards

Ingo

[curiouscat]

that would be ballpark bulk prices in Europe, based on 100 kgs  / shipment CF RoAn
If, however, you became a real huge consumer (like: 100 metric tons/year) and if you imported from, let's say India, you'd significantly would reduce prices down to approx. 1500 euro / metric ton  (approx 1 US-$ per pound)

Yes, $1-3 / lb sounds more reasonable to me. It is a bulk chemical after all.

I did a quick estimate and I think we'll end up using not quite 100 tons / year but say 20-30 tons I think.

[curiouscat]

They really do rip you off for small orders; that's a 15x price markup we see, and 100 kgs is not that small a quantity after all! 

I cringe to see how much Sigma will charge for a kg or two. Probably a 100x markup on bulk prices. 

[magician4]

Sigma in Europe goes at approx 100 Euro / kg (~ 62 US-$/lb ,  1 kg single order)
http://www.sigmaaldrich.com/catalog/product/sial/223468?lang=de&region=DE


... at that's about the level for other lab-suppliers in general  here, too


regards

Ingo

[curiouscat]

As a supplementary question:

For a KMnO4 oxidation is it necessary / recommended to acidify the reagent? I'm trying to oxidize benzaldehyde. Often I see H2SO4 added for KMnO4 based oxidations.

[magician4]

the oxidation potential of MnO₄^- is highly pH- dependant: with slightly alkaline to ~ neutral conditions you'll end up with MnO₂ , i.e. 3 electrons per permanganate , under acid conditions with Mn²⁺(aq.) (i.e. 5 electrons per permanganate)

"acid" to the best of my knowledge means pH < 3


regards


Ingo