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Fulmen
International Hazard
Posts: 1716
Registered: 24-9-2005
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I'm sure you're right. It was nevertheless too impure for my taste, so I didn't see any other choice than to blow some of my precious SA on it.
We're not banging rocks together here. We know how to put a man back together.
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AJKOER
Radically Dubious
Posts: 3026
Registered: 7-5-2011
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Found a source (see 'Bonding Analysis of the [C2O4]2+ Intermediate Formed in the Reaction of CO22+ with Neutral CO2' by Ferran Feixas, et al., in J.
Phys. Chem. A 2010, 114, 6681–6688 6681, link to full text: https://pdfs.semanticscholar.org/aee0/2cc27bee5b913b0a1584d6... ) that basically describes an unstable intermediate [C2O4]2+ that decomposes into
CO2(2+) formed in a thermal reaction.
Bottom line, a questionable path to oxalate.
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Fulmen
International Hazard
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Whatever, I don't see it as germane to this topic. My initial focus was to investigate formates as a precursor to other useful chemicals. Oxalic acid
was the first thing to come up, and last time I looked at oxalates I could only find the nitric acid/sucrose synthesis.
The OA synth is pretty much nailed, I don't think I will spend too much effort on improving the yield. So what else could we make? Formaldehyde sounds
interesting, but it poses some additional challenges as the product is gaseous. Also I don't care much for the smell, so I'd like to find a synth that
can use the formaldehyde directly. Urea-formaldehyde might be worth some study.
We're not banging rocks together here. We know how to put a man back together.
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WGTR
National Hazard
Posts: 971
Registered: 29-9-2013
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Glyoxal. If you want a challenge. But maybe that was a rhetorical question.
In fact, oxalic acid is one oxidation product of glyoxal. If you found a way to reduce it back to glyoxal, that would be very cool, but undoubtedly
very difficult and probably impractical.
Gyoxal is normally made by the careful nitric acid oxidation of ethanol/acetaldehyde. If made in the gas phase it can remain so. If, however, it is
allowed to condense with a tiny bit of moisture it instantly polymerizes, and remains non-volatile up to its decomposition temperature.
Purification of glyoxal made by the nitric acid process is difficult, since the di-aldehyde is non-volatile. As the acid is expended the reaction
stops. Upon gentle evaporation the dilute acid concentrates further, and the reaction starts again. I've seen the reaction run away with dense red
fumes after it was seemingly completed.
The product contains numerous impurities: excess nitric acid, oxalic acid, glycolic acid, and glyoxylic acid are the main ones. Some of these side
products are interesting in and of themselves. The reaction mix can be neutralized, but only with calcium carbonate. Other carbonates or hydroxides
will perform a nasty little Cannizzaro reaction on the aldehyde.
I've read of ion-exchange membranes being used to remove the salts from glyoxal. The old literature from the early 1900's used barium and lead salts,
if I remember correctly. That produces nasty waste products. I was thinking of using a form of capacitive deionization, but haven't gotten around to
trying yet. I would have to make the electrodes for it.
What is glyoxal used for? Making N-methylimidazole via the Debus-Radziszewski imidazole synthesis. Some of the N-methylimidazolium chloride salts can be purified by melt-zone crystallization, using a hot
wire looped around a slowly moving glass tube containing the salt. The purified salt is used to make N-methylimidazolium ionic liquids. These are
used as room temperature molten salts for battery and supercapacitor chemistries. If you try to buy them, they are pretty expensive in small
quantities ( I wonder why?).
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Fulmen
International Hazard
Posts: 1716
Registered: 24-9-2005
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Sounds interesting, but it's a little too ambitious for me.
We're not banging rocks together here. We know how to put a man back together.
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