02-19-03 14:37
No 409755
Hi all. Been playing, and decided to see if I could make some peroxalic acid, seeing as it appeared that no-one had tried it (I used TFSE as thoroughly as I could...)
OK, first of all. Tried to tan some hides a while back (miserable, SMELLY failure...), but it meant that I had half a container of lab grade oxalic acid lying around. Couldn't get my hands on any H2O2, but read that Sodium Percarbonate would work as a substitute. So, I took a couple of spoonfulls of oxalic, added a fair heap of 27% Sodium percarbonate washing powder (the rest, I assume, would be sodium carbonate and a little soap powder, judging from all the bubbles!). Add water, the whole thing goes crazy. Gas was evolved (not a huge amount, and stupidly I didn't even do a basic flame test to see what it was! Next time! I would, however, guess that it would be CO2). There were no indicators of what happened, so I added about 1mL of 30% HCl. The solution went almost instantly a light yellow-green colour, and stayed that way. I seem to remember reading somewhere that a peracid has a yellow tinge (or am I deluded?), so I took this as a promising sign (did the acid act as a catalyst - peroxalic acid should form rapidly, faster then performic, but would HCl help?), as I have never made or used a peracid of any type before and thus didnt really know what to look for. Either that, I thought, or it could be chlorine being oxidised by the peroxide. I tested this by mixing up some of the washing powder in water and adding a heap of HCl - the solution went a darker green but cleared up reasonably quickly. Also, CO2 (I assume - flame test) was evolved (from HCl + Na2CO3?) in large enough amounts. I was unable to do further testing, but I think this bears further investigation. Oxalic acid has a pKa about 1 less than Formic (which is in turn 1 less than acetic. And no, I cant remember exact values off the top of my head). This could lead to incresed yield, or at least decreased reaction time, if used as in a buffered performic...
(Chief Bee)
02-19-03 22:24
No 409848
The only synthesis of your target compound in the literature is from JACS 68, 534 (1946) and reads as below - I highly doubt that you could make it your way.
Diperoxalic Acid
When oxalyl chloride (Prepared according to Staudinger, Ber., 41, 3563 (1908)) was treated at 0°C with an ice-sodium peroxide mixture, it was hoped to obtain a carbon peroxide, C2O4, or one of its polymers. Neither one of these peroxides was obtained, but instead a small yield of diperoxalic acid. A higher yield of this diperacid was obtained by the following, somewhat different, procedure: To a solution of 19 g. of dry pyridine, 285 mL of anhydrous ether containing 4g. of hydrogen peroxide and maintained at -20°C, was added, dropwise in the course of two hours and with vigorous stirring, a precooled (-10°C) solution of 75 mL of anhydrous ether containing 14.3g of oxalyl chloride. At the end of the reaction, the ether layer was decanted and the solid precipitate, which had separated out, extracted with two 100 mL portions of anhydrous ether. The residue was then treated with an ice-cold mixture of 60 mL of saturated sodium sulfate solution and 40 mL of 85% orthophosphoric acid. The resulting mixture, after adding more solid sodium sulfate, was extracted with three 100 mL portions of acetone which was combined with an equal volume of ether and the mixture dried and filtered. When the solvent was removed under reduced pressure, a highly viscous residue (2.2 g.) remained which failed to crystallize on standing for some time at 0°C. This product was free from chlorine and nitrogenous products, and was found to be very soluble in water and chloroform. Diperoxalic acid is a powerful oxidizing agent, and, when treated with potassium iodide, it is reduced rapidly to oxalic acid.
(Stranger)
02-20-03 13:30
No 410106
Rhodium, as far as diperoxalic acid is concerned, I think I agree with you - it would be highly unlikely to form under the conditions I put forth. What I was thinking, however, was that the monoperacid (C2H2O5) may have been formed. It seems logical. Oxalic should react in a similar manner to formic acid, and has a lower pKa (1.27 for the first H as opposed to 3.6 for formic) and thus should react faster. I see no reason why this shouldn't work, and the empirical evidence demonstrates SOMETHING happened - and I can't really think what else could have been (unless the oxalic had some funky reaction with the soap powder, which is probably unlikely). Is there some (reasonably) simple test I could do to determine if a peracid really did form (other than epoxidising an alkene)?
(Chief Bee)
02-20-03 15:36
No 410137
Titrate with potassium iodide and see how much Iodine forms, possibly by titrating the iodine with thiosulfate.
(Stranger)
03-03-03 09:01
No 413280
OK, sorry I haven't been here for a while, but anyways. I have been unable to do any quantitative tests as suggested Rhodium, but I did do a more basic version of the iodine test. To a solution of (supposed) peracid was added some KI, along with a small amount of starch solution. The presence of iodine (I2) was confirmed by the blue colour. Thus it would seem that monoperoxalic acid was formed. However, my first trial (using sodium percarbonate as a peroxide source) failed to cause formation of iodine, so I used stronger (62%) peroxide, freeze purified from 6% solution and some water to dissolve everything. Perhaps the use of percarbonate would require the acid mix to sit for a while and/or a strong acid catalyst (like for peracetic), or perhaps the concentration would need to be increased. In any case, it would seem that peroxalic is a possible substitute for performic/acetic. If someone else would like to try this and provide some confirmation of my results (perhaps with some bloody measurements!!) it could prove very interesting... Also a test epoxidation by someone with the resources could be tried - if someone's interested in going that far, I would think that something equivalent to a buffered performic could prove quite effective.
(Obsolete)
02-20-04 11:31
No 489945
This would be a great route,
What do we need to do to test it?
This would also be a great otc refinement for peracid dreams,.
hm
I went down to the depot of evolution, and ordered the man to supply me enough, to last a lifetime..