oxidation of diols

oxidation of ethylene glycol to oxalic acid

HO-CH2CH2-OH + 8HNO3 --> 8NO2 + HOOC-COOH + 6H2O

Preliminary
Yesterday I recovered about 75 mL of ethylene glycol from antifreeze by fractional distillation. Column packing was a ss scrub pad. This antifreeze contained, besides EG, diethylene glycol, water, dipotassium phosphate, corrosion inhibiters, defoamer, silicates, and dye.

The distillation went very well with a little water coming off first right at 100C, then the EG came off cleanly at 196-197C. I started with 125 mL and left about 25 mL in the pot. It's not like I have any shortage of antifreeze.

Oxalic Acid Procedure
The following procedure is based on "Oxidation with Nitric Acid of Aliphatic Alcohols and Diols to Carboxylic Acids" from the Russian Journal of Organic Chemistry, 2006. My thanks to forum member sonogashira for this paper.

Today 5.6 mL (0.1 mole) of EG was placed in a beaker and 33 mL (0.5 mole) of 68% nitric acid (the azeotrope) was added and stirred. Temperature only rose to 30C from room temperature. This was then placed in a 100 mL RBF suspended in a silicone oil bath under temperature control at 88C. For some minutes nothing was happening although I could see a little brown coloration, indicating production of NO2. My PID controller wasn't properly tuned and the temperature rose to 97C. Still no action. Then, all of a sudden there was a runaway with copious amounts of NO2 generated. I quickly turned on the hood fan which immediately vacated the brown fumes filling the hood space.
Things did settle down without any boilover. The reactants were kept stirred in the bath for a total of 4.5 hours.

The products were set aside to cool to room temperature whereupon crystals (needles) of putative oxalic acid formed. These were Buchner funnel dried with no wash. After air drying 2.3g of crystals were obtained for a yield of 25%, assuming the crystals are not hydrated.

Discussion
This synthesis was done only to determine the viability of the Russian procedure for making dicarboxylic acids from diols. The expected yield was 69%, so that is a little disappointing. But there was no char, and I did use 68% nitric acid vs the prescribed 80% nitric acid. There may be better procedures for making dicarboxylic acids but the viability of this one is established for me. The workup is extremely simple.



[Edited on 19-9-2009 by Magpie]



[Edited on 19-9-2009 by Magpie]

[Edited on 19-9-2009 by Magpie]

Quote: Originally posted by Magpie

The following procedure is based on "Oxidation with Nitric Acid of Aliphatic Alcohols and Diols to Carboxylic Acids" from the Russian Journal of Organic Chemistry, 2006.

This has already been mentioned.

Thank you entropy, I can likely find that journal at my local library.

I agree that my crystals are probably oxalic acid dihydrate. I'm just too lazy to dry them and determine a mp. That would be the safe thing to do, however.

It's interesting that they claim 6N HNO3 is best. The Russians make the same claim for 75-80% HNO3.

Edit: Thanks for the reference link. I didn't know that they did anything serious at Reed College.

[Edited on 20-9-2009 by Magpie]

[Edited on 20-9-2009 by Magpie]

This is the right approach when doing this type of reaction on an experimental basis. After hosing down everything in the hood with water I prepared to try it again. This time I would go half scale and add the diol with a pressure equalizing funnel.

I first added 3 drops of diol to the acid before any heating. Then I gently heated until that small amount of diol began reacting. Then removed the heat and added the diol 5 drops at a time as the reaction subsided. This kept everything under good control. After all the diol was added the RBF was placed in a silicone oil bath set at 105C and heated for another 1/2 hour.

I can see now why only a 5:1 mole ratio of nitric acid to diol is needed. The nitric is mostly reduced to NO, not NO2. This is most graphically seen at the top of the reflux column where the clear gas rising in the column is converted to NO2 as it contacts the O2 in the atmosphere. So, this is probably a more correct stoichiometry:

3HO-(CH2)3-OH + 8HNO3-->3HOOC-CH2-COOH + 8NO + 10H2O

I now have the putative malonic acid products sitting in an evaporating dish. I don't want to go through an ether extraction. For one thing I don't see how it can be very effective when the solubility of malonic acid in water is 1g/0.65 mL water. I am planning on doing another batch where I will convert the malonic acid to diethyl malonate. This may be the most effective way to recover the acid itself, also.

Any suggestions for workup of the malonic acid are welcomed.



[Edited on 24-9-2009 by Magpie]

Quote: Originally posted by Magpie

re: not_important ... During the evaporation a lot of small bubbles were generated along with a fair amount of NOx. I hope those bubbles were NOx and not CO2. At 135C this is supposed to happen: HOOC-CH2-COOH ---> CH3COOH + CO2 How important do you think it is to evaporate at reduced pressure?

I decided to keep my malonic acid product on the steam bath until no more NO2 evolved. As the liquid volume decreased more NO2 evolved. I added a few mLs of water twice. After that I just heated it until NO2 stopped evolving and it was nearly dry. At this point it was rehydrating as fast from the steam bath vapors as it was losing liquid from the heating. I then placed it in my drying oven, set at 70C, for 2 hours. I then weighed it and took a melting point. If the mp was not satisfactory I was going to try washing it with very cold DCM. But the mp, or decomposing point, was 137C vs my literature value of 130-135C. The weight is 4.8 g for a yield of 46%.

I'm very satisfied with this method for making malonic acid, especially in comparison to the classical method that uses KCN. Further procedure refinement would no doubt result in increased yield.

Thanks to Pantone159 for the idea of using 1,3-propanediol as precursor, way back when. Thanks also to entropy51 for the reference from J. Chem. Educ.



[Edited on 25-9-2009 by Magpie]

I also thank BromicAcid. Apparently he was the first to mention the use of 1,3-propanediol for making malonic acid.

I certainly miss his contributions and prolific experimental work. But I have a feeling he'll be back...someday.

[Edited on 26-9-2009 by Magpie]

Quote: Originally posted by Magpie

I also thank BromicAcid. Apparently he was the first to mention the use of 1,3-propanediol for making malonic acid. I certainly miss his contributions and prolific experimental work. But I have a feeling he'll be back...someday. [Edited on 26-9-2009 by Magpie]

What he get 18 to life?
LMAO sorry I couldn't resist. Its friday and late. I sure hope Im not correct because that wouldn't be cool at all and make my crappy jokes just ignorant. I always liked bromics post though.

[Edited on 26-9-2009 by Sedit]

Quote: Originally posted by Sedit

I see mentioned in this thread the suggestion of adding the HNO3 to the hot glycol, could you explain what advantage this would have?

From

A Dictionary of Chemical Solubilities, Inorganic 2nd Ed. Comey

Available at the Internet Archive and Google Books

(and yes, the calcium nitrate file is just CaNO3... because Ca(NO3)2... has some potential filesystem squibble.


I don't see your reasoning matching what would happen, I think that a runaway is even more probable. Also, given the near anhydrous conditions I'd expect EtONO2 to form.

If nothing else I'd dissolve the H2SO4 in some EtOH first, so as to avoid thermal input from it reacting with the alcohol in the nitrate mix. More heating drives the reaction faster, that's what the runaway is about, the heat of the reactions speeding up the reactions even more.

(remember - babies bottoms may be smooth, but consider the high volume of you-know-what that comes out of them :-)


Personally, I don't see the reason to waste expensive or increasingly difficult to obtain oxidisers on simple lower alcohols; I'm a bit puzzled as to why you've chosen this route.





[Edited on 25-6-2010 by not_important]

Quote: Originally posted by not_important

From I don't see your reasoning matching what would happen, I think that a runaway is even more probable. Also, given the near anhydrous conditions I'd expect EtONO2 to form. If nothing else I'd dissolve the H2SO4 in some EtOH first, so as to avoid thermal input from it reacting with the alcohol in the nitrate mix. More heating drives the reaction faster, that's what the runaway is about, the heat of the reactions speeding up the reactions even more. Personally, I don't see the reason to waste expensive or increasingly difficult to obtain oxidisers on simple lower alcohols; I'm a bit puzzled as to why you've chosen this route. [Edited on 25-6-2010 by not_important]

Quote: Originally posted by Sedit

Lambda, Nitration is much more hazardest then this reaction yet everyone seems to have no issue running that daily. This is not going to sit on the shelf for anytime so the dangers associated are null.

I found that using an old stainless steel deep fryer that I modified for steam generation to be the best means of concentrating the NaOAc since it has ability to boil off gallons of liquid in a matter of minutes instead of hours. I will have to give IpOH a shot if I ever go that means again but even though im a huge kitchen chemist even this seemed a little excessive for 500 grams or so of NaOAc. Ill take electrochemical means that produces NaOAc from EtOH over evaporation of that much liquid again but thats a method of the acetic acid threads.


I had a chance to attempt the HNO3 oxidation at a one more scale of acid which I sort of botched but showed some interesting results to me anyway. I used 1:1 KNO3-H2SO4 with 20ml of H2O to increase the fluidness of the acid when I could have gotten away with 1:0.5 nitrate to acid ratio but was not thinking. However after reading abstract after abstract over the past few days I decided I was going to start with the addition mol of EtOH the paper recommends of .2 mol or something on the order of around 10 grams of EtOH and slowly add more until NO2 stops being released. After getting all the way to 50 grams of EtOH and still showing signes of NO2 I stopped because this does not make much sense to me.

The reaction contains the initial NO2 ions needed for initiation of the reaction from over heating as the H2SO4 is added presumably. Drop by drop I started to add the EtOH to warm acid and stand back to observe. At first I thought stirring would be good but this causes heavy foaming and I found if I just leave it as is it starts a relatively mild cycle that was not hard to control with addition rate at all. I would still take much caution for the first few grams of addition since it does show potential for going out of hand. A cold water bath was used for cooling and I think Ice would be much better since alot of heat is generated at the start of this reaction and with NO2 already present it does not need an initial heat source to get it going.

One drip of EtOH is enough to cause all of the NO2 to vanish instantly from the flask leading me to think the NO2 ester plays an important role in the oxidation of some kind.

Even after breaching 1 mol of EtOH there is still signs of NO2 but much calmer then before and the entire reaction is now fluid with the Potassium bisulfate almost completely dissolved. This would precipitate at the start and I attribute this to the sulfates solubility in AcOH and insolubility in EtOH where as it could also be in solution from H2O formed in the reaction, that is yet to be seen.

The smell of AcOH(Dont sniff the FLASK drip it on blotter paper) is very very strong now after a slow warm water bath that lasted a couple days since I was allowing it to react then add a little more and so on....

Its non flammable by any means at this point.

Why would this reaction still show signs of NO2 generation even after 1 mol of EtOH? I hypothesized that I may be able to do about .5 mol but not 1. Could the acidic nature of KHSO3 be affecting the reaction somehow?

I wish I had a GC or some means of analysing stuff like the big boys do but its hard here down on the bottom. Still betcha I have more fun doing what I do for free then they do for money

I obviously have alot of work to do before I could give a definitive yeild. I am going to add a few drops to Sodium bicarbonate and see how wet it stays after its done reacting. NaOAc should be relatively dry where as H2O and EtOH would leave it damp afterwards. And it will allow me to smell for the presence of EtOH, AcO, and any esters that may form. Freezing the reaction mixture would be a good idea as well if it can indeed freeze. I want to have a good idea whats in the mixture before I distill it because all this talk of EtOH and Nitric acid forming explosive mixtures has got me a little uneasy.

Where did all the stuff go???

I tried to repeat Julius B. Cohen's method for oxidising sucrose to oxalic acid with conc. nitric acid and V2O5 but with remarkably little success so far.

I don't have any conc. HNO3, only 38 w% (6N), so had to adapt the recipe. I ended up with a hybrid between Cohen's and Magpie's (first post in this thread), figuring that sucrose could very loosely be described as a hexamer of ethylene glycol.

Cohen calls for 20 g sugar (sucrose), 140 ml conc. HNO3 and 0.1 g of V2O5.

I cooked up 10 g, sugar, 140 ml 38 % HNO3 and 0.05 g of V2O5, by adding the sugar to a hot (steam bath) mixture of the nitric and the catalyst. Based on Magpie's first attempt, this is somewhat sub-stoichiometric in HNO3.

Ready for a run away, instead the solution turned green (V(H2O) +3) first and slowly started fuming NO2. That fuming build up until thick oodles of brown smoke bellowed out of the flask but without any run away: the solution was boiling away nicely.

After an hour or so on the steam bath the reaction started slowing down and the boiling stopped. I transferred the liquid to a Pyrex jug and started to heat with a small direct flame, for about another hour, topping up the liquid with water so that the level didn't fall below 100 ml. At the end the fuming had all but stopped and I reduced the green solution to about 40 ml, cooled and even chilled it but no crystals of HOOC-COOH where forth coming.

The next day the solution was carefully reduced to almost nothing and a reddish precipitate formed: hydrated V2O5? But little else was found. I filtered the solution, the filtrate ran green. But adding concentrated Ca2+ yielded no calcium oxalate...

I tied again, this time 5 g sugar, 115 ml 38 % HNO3 + pinch of V2O5. Assuming sucrose is about (EG)6, this is then stoichiometric in HNO3. The procedure above was used.

This time, after careful and complete evaporation, an amber-reddish crystalline mass was obtained probably less than one gram though. This dissolved effortlessly in water, turning clear green in the process. Added anh. CaCl2, this dissolved effortlessly, without any calcium oxalate forming!

Am I overheating this stuff and oxidising also the oxalic acid, or what is going on here???

One more attempt will be made with 5 g sucrose, 115 ml 38 % HNO3, no V2O5 and cooling on a cold water after the reaction starts...

Quote: Originally posted by Paddywhacker

If the oxidation is going too far, then maybe more sugar or less acid would do the trick. Also, adding the acid mixture to boiling sugar solution will stop the acid being in excess.

Cohen actually recommends adding the sugar to the acid. I can't really see it make much difference but I could be wrong on that. I believe an excess of nitric is better than not enough but it's more an article of faith than anything else...

Third attempt: this time a mixture of 5 g sugar and 115 ml of 38 % HNO3 (no V2O5) was gradually heated on the steam bath. It took decidedly longer for the reaction to start but once started, it's indistinguishable from a reaction that includes the catalyst. Interesting to note is that the solution also turned green, as in the presence of V2O5.

Taking the bottle off the steam bath and the reaction stopped. I see little point in doing that, so continued with the steam bath for about 2 hours, until NO2 elution had subsided much. That was then left to stand, quasi-stoppered, overnight.

The flask, with camera shake, just after taking off the steam bath. It was then returned to it:



The 100 or so ml of liquid left was transferred to Pyrex receptacle and simmered under partial reflux. The oxidation reaction started up again and continued for about an hour or so, with the solution also picking up a brownish colour. At about 50 ml it was transferred to a smaller Pyrex receptacle and gently boiled in to almost nothing. It dried, showing plenty material, including some black stuff. It seems that right to the end some oxidisable saccharide remains, which then carbonises at the end.

The Pyrex jug, after gentle boiling (with camera shake): the head space is still full of NO2:



After the smoke has cleared: whitish/yellow mass with a black spot. White material can also be seen on the inverted glass lid (right):



To the solid material was then added 10 ml of water: most of it dissolves but not all. It was heated on steam bath for some time, then filtered. The filtrate is clear but brownish. On the filter: a white powder. The powder was isolated. It doesn't dissolve in water but it does dissolve in an excess of strong HCl: an oxalate? It will be neutralised with NH4OH and checked for oxalate.

The filtrate was gently evaporated on steam bath until almost nothing, then left to dry: needle like structures so typical of oxalic acid developed (hard to see in the photo below). Unfortunately the brown muck did not separate out much and the amount of material is very small. Rough yield to be determined yet but it seems to me that the oxidation of ethylene glycol with diluted nitric (Magpie and other sources) works well, but not the oxidation of sucrose for which much stronger nitric is needed for more quantitative yields...



I wonder if improvement could be obtained by carrying out the whole operation on steam bath, from reaction to evaporation of water...


[Edited on 25-7-2010 by blogfast25]

Well, a fourth attempt did work: this time 200 ml HNO3 38 % and 8 g of sugar, a ratio I believe uses a slight excess of HNO3.

Most of the reaction was carried out on steam bath, then paused overnight and finished off by gentle simmering. The last 100 ml or so were evaporated on steam bath. NOx continued to elute up to the last moment.

5 - 6 g of crude oxalic acid, slightly wet and very slightly yellowish:



The crude has been worked up with three precise recrystallisations.

So it's possible to make oxalic acid even from sugar with fairly dilute HNO3. But it will work faster and better with azeotropic or higher HNO3...

You can make formaldehyde from it too, at least according to these Authors (they use Lead Dioxide and acetic acid, forming the tetraacetate in-situ

Quote: Originally posted by blogfast25

The powder was isolated. It doesn't dissolve in water but it does dissolve in an excess of strong HCl: an oxalate? It will be neutralised with NH4OH and checked for oxalate.

Quote: Originally posted by Formatik

In Beilstein it's said that oxalic acid stubbornly retains alkalis, method for purification given there recrystallizes from boiling 10-15% HCl. Then washing with a little cold water and recrystallizing from alcohol. [Edited on 31-7-2010 by Formatik]

Quote: Originally posted by un0me2

Funny, oxalic acid is one of the few I can purchase no questions asked. They use it for a huge number of reasons, look for it via google "oxalic acid msds" normally works for me.

Quote: Originally posted by not_important

OK A) I found that using s slow cooker to evaporate the neutralised vinegar until you've got essentially liquid NaOAc.3H2O, then slowly pouring that into chill i-Pr alcohol with good stirring, gives a pretty clean precipitate of the acetate, partially dehydrated to the monohydrate. Washing the ppt with several small amounts of further chilled IPA removes much more of the colouring; after a single wash with IPA, adding a bit of water the the acetate and going through the melt-evaporate-pour and washing the precipitate twice gave me a white product without much loss (the trihydrate's solubility in EtOH is around 50g/l, in IPA it's lower) A dichloromethane extraction of the powdered solid acetate also might give good results. In either case sugars in the vinegar would remain with the organic solvent insoluble portion, but as they're non-volatile the distillation of the AcOH should take care of them. I'd also consider the oxidation of EtOH by NaOCl catalysed by nickel salts (which form NiOOH/NiO2). Filtering removes the nickel, evaporation leaves NaCl and NaOAc.3H2O In either case I believe it is important to avoid localised overheating when adding the strong acid to the NaOAc. Dispersing the acetate in acetic acid and slowing adding H2SO4 seems to work, a similar approach is used for formic acid when the dehydration to carbon monoxide can be a real problem.