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clearly_not_atara
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Yeesh. I knew making BBr3 was hard, but I didn't think it was bromine at 325 C hard.
Pyridinium hydrochloride is reported as an effective demethylating agent. I've always secretly suspected that pyridinium hydrobromide might be even
better.
CuReUS is right: unsubstituted o-quinones are unstable. O-quinone undergoes Diels-Alder reactions with itself, forming strange side products.
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Melgar
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If I can do the niacin to pyridine decarboxylation, then I'll look into pyridinium chloride and/or bromide. I think the chloride is because halogen
exchange would make the bromide pointless and potentially complicating, since AlCl3 is also present, no?
With the type of videos we want to show, unorthodox routes and reactions that haven't been documented are actually preferred. The idea we
want to convey is that you don't need to have a state-of-the-art lab to make new discoveries in science. Like, new scientific discoveries are within
reach of anyone of moderate means.
I have boron carbide and bromine, the trouble is finding anything that won't instantly be eaten through by bromine at 325C. Besides boron carbide,
apparently. The only way it'd be possible is by sealing it in a glass tube, but the tube would have to be at least 20-30 cm long, so the bromine
wouldn't boil away as you melted the glass.
[Edited on 11/9/17 by Melgar]
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JJay
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I don't have any boron carbide....
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clearly_not_atara
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| Quote: | | I think the chloride is because halogen exchange would make the bromide pointless and potentially complicating, since AlCl3 is also present, no?
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No, the reaction uses pyridine hydrochloride alone with strong heating (microwave):
"Basically the microwave demethylation fucking rocks, as far as ease goes, but the downside is because you need 5:1 pyridine HCl:eugenol."
"I made my pyridine HCl by gassing pyridine with anhydrous HCl gas, this was pretty easy (just gassed it for a while, some crystals formed but it was
quite hot so i froze it, many more crystals formed, filtered it, washed with ether, then put the crystals on the bench to dry, came back, almost no
crystals left and very sloppy, note-they are very deliquescent and they sublime so put them in a closed container immediately post production."
"All I did was added eugenol in the weight ratio five parts pyridine HCl two parts eugenol (this is molar 5:1), put this in a round bottom flask,
stoppered it, microwaved in a normal microwave on medium low (the paper uses 215 watt oven) for two minutes, the stuff melts and turns quite hot, it
was removed, cooled under the tap until it was room temp again (just felt it with my hand), then microwaved again for two minutes etc etc, this
process was repeated six times, the more you do it the hotter it gets each time. After the sixth time i cooled it again, poured some cold water from
the fridge into into it and extracted it three times with ether, pooled the ether extracts, removed the ether on the rotavap, the residue had no smell
of clove oil whatsoever, just the smokey smell of the demethylated product, so i assumed quantitative yeild cause I couldn't be fucked vac distilling
a room temp solid and/or GC'ing it, also the methylation requires an excess of all other reagants anyway."
[Edited on 9-11-2017 by clearly_not_atara]
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Melgar
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Got five bucks?
https://www.ebay.com/i/181516028071
It's also a commonly-used sandblasting grit, so I'd consider it OTC for all practical purposes.
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JJay
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It's about as OTC as iron oxide... but I think you can use boric acid or borax with carbon too.
It looks like higher temperatures reduce the amount of bromine required: https://www.google.com/patents/US2989375
Edit: I should probably point out that I'm having some difficulty finding a credible reference for the temperature of 300 C quoted in various places.
[Edited on 9-11-2017 by JJay]
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Melgar
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Quote: Originally posted by JJay  | It's about as OTC as iron oxide... but I think you can use boric acid or borax with carbon too.
It looks like higher temperatures reduce the amount of bromine required: https://www.google.com/patents/US2989375
Edit: I should probably point out that I'm having some difficulty finding a credible reference for the temperature of 300 C quoted in various places.
[Edited on 9-11-2017 by JJay] |
Hmm. What about a fused-quartz reaction area, heated to red hot with a torch, containing boron carbide? Say, a length of tube, bent slightly in the
center so the boron carbide stays there. Run bromine through the reaction area in a loop by collecting the distillate in a non-pressure-equalizing
funnel, then adjust the flow rate on the funnel to send more bromine through the reaction area? Not sure how to make a fused quartz tube part of a
closed loop for bromine distillation, but if that could be solved, it seems straightforward otherwise.
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JJay
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Continuously recycling the bromine in a reasonably-priced setup is going to be tricky.
[Edited on 10-11-2017 by JJay]
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Melgar
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Oh, I just meant use borosilicate for everything except the hottest part where the boron carbide is. It could also be open to the air, via a vigreux
column or something, since bromine vapors are easy to see. Really though, I wouldn't bother with that since bromine barely generates any pressure in
a closed system, assuming the vapors can easily flow to cooler parts. There needs to be vapor movement though, and what you seem to be suggesting
could result in an equilibrium, with very little bromine ever being able to come in contact with the boron carbide.
Boron tribromide has a boiling point of 91C, apparently. Wikipedia is saying it's soluble in ethanol but reacts violently with water. Usually a
violent reaction with water implies a somewhat less-violent reaction with ethanol, but perhaps not in this case?
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JJay
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It would be easiest to recycle the bromine manually. But according to that patent, if the temperature is high enough, it will all be consumed.
I would personally not try using a sealed system for 900 C bromine at home except maybe a small sealed test tube, but I'd prefer to have more than a
tenth of a gram of boron tribromide to play with. I'd just drop it or boil the vapors through the hot zone and condense them in another part of the
apparatus, fractionally distill, and recycle the excess bromine.
Aluminum tribromide looks easier to make than boron tribromide. I wonder if you can make sodium borohydride by reacting boron tribromide and sodium
hydride....
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wakatutu
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Since people are asking about it, I have never seen a write up of an amateur successful with producing protocatechualdehyde via ether cleavage. I had
read someone post on this site, I think, where the notion of using sulfuric acid to cleave vanillin was dismissed but the same procedure was said to
be effective with ethyl vanillin.
I will have to post some lab notes on here when I get back to my home area. But from here, on my phone at work, I can at least say some of the basics
about the reaction. I first tried it with my ample supply of vanillin. The idea is to dissolve the aldehyde in sulfuric acid at 0C, then heat the
mixture for some time on a steam bath. The work up is to drip the acid solution into ice water, which causes the unreacted vanillin to precipitate,
leaving the catechol aldehyde in aqueous solution. The aqueous solution is then extracted with diethyl ether.
This was highly ineffective with vanillin. Yields were there but very very low. Then I bought some ethyl vanillin after several attempts and
failures. This substrate was magical for this process. Upon dripping the acid solution into ice water, no precipitate formed. Ether was used to
extract, was distilled leaving behind a crystalline solid with a bit of purple tint. The reaction prior to extraction smelled of ether due to
dehydration of the formed ethanol.
Further studies in this area led to methylenation with DCM in DMSO which resulted in heliotropin at a yield of 36% on starting protocatechualdehyde.
I had wanted to avoid ether but after attempting to use DCM, and being unable to resolve the formed emulsion and finding the same with chloroform and
finding alkanes and aromatics to be poor solvents for this, ether turned out to be the easiest solvent to extract this with.
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Melgar
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| Quote: Originally posted by wakatutu | Since people are asking about it, I have never seen a write up of an amateur successful with producing protocatechualdehyde via ether cleavage. I had
read someone post on this site, I think, where the notion of using sulfuric acid to cleave vanillin was dismissed but the same procedure was said to
be effective with ethyl vanillin.
I will have to post some lab notes on here when I get back to my home area. But from here, on my phone at work, I can at least say some of the basics
about the reaction. I first tried it with my ample supply of vanillin. The idea is to dissolve the aldehyde in sulfuric acid at 0C, then heat the
mixture for some time on a steam bath. The work up is to drip the acid solution into ice water, which causes the unreacted vanillin to precipitate,
leaving the catechol aldehyde in aqueous solution. The aqueous solution is then extracted with diethyl ether.
This was highly ineffective with vanillin. Yields were there but very very low. Then I bought some ethyl vanillin after several attempts and
failures. This substrate was magical for this process. Upon dripping the acid solution into ice water, no precipitate formed. Ether was used to
extract, was distilled leaving behind a crystalline solid with a bit of purple tint. The reaction prior to extraction smelled of ether due to
dehydration of the formed ethanol.
Further studies in this area led to methylenation with DCM in DMSO which resulted in heliotropin at a yield of 36% on starting protocatechualdehyde.
I had wanted to avoid ether but after attempting to use DCM, and being unable to resolve the formed emulsion and finding the same with chloroform and
finding alkanes and aromatics to be poor solvents for this, ether turned out to be the easiest solvent to extract this with. |
Indeed, there seems to be a lot of hinting at the existence of some original "Q document" describing the dealkylation of ethyl vanillin, but I've
never been able to find that document. Thanks for adding that additional information, both about the reaction and about the solubility difference
that's used for workup.
I'm really looking forward to planning out this video series now. There was another series we were going to do called "how to do chemistry unsafely",
where a mannequin with poor impulse control attempts to do chemistry and makes all sorts of common mistakes that blow up in his face, often literally.
I thought that would be a lot of fun, but now I'm having trouble deciding. 
The first step in the process of learning something is admitting that you don't know it already.
I'm givin' the spam shields max power at full warp, but they just dinna have the power! We're gonna have to evacuate to new forum software!
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AvBaeyer
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Isovannilin is synthesized by methylation of ethylvanillin then selective removal f the ethyl group by treatment with sulfuric acid. This has been
published at least once in JACS which you will need to look up as I do not have the reference at hand so you will have to look it up. I have not
looked specifically for a reference for delkylation of ethylvanillin.
AvB
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JJay
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This looks pretty interesting: http://www.sciencemadness.org/talk/viewthread.php?tid=28035#...
They discovered reaction conditions for preparing 3,4-dihydroxy mandelic acid, which can be oxidized to protocatechualdehyde. They had some issues
with singularities and resolved them using partial least squares (I think you'd get the same results with SVD). Their targets were various flavoring
compounds, but as we know, protocatechualdehyde is a couple of easy reactions away from dopamine.
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