madscientist
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Oxamide synthesis
I just tried to synthesize (CONH2)2 via the following method:
2CH3CH2OH + (COOH)2 --(H2SO4)--> (COOCH2CH3)2 + 2H2O
(COOCH2CH3)2 + 2NH3 --> (CONH2)2 + 2CH3CH2OH
After about an hour of gentle heating, there was still a fine white powder on the bottom of the beaker. I was using several times the stoichemitric
amount of CH3CH2OH. I allowed it to sit for 36 hours at 18C. I then filtered it, and poured the filtered solution into a beaker of 10% NH4OH. Now, my
sulfuric acid is yellowish-brown, but that still doesn't explain what happened: I ended up with an intense orange solution! There was a fine white
precipitate at the bottom of the beaker (CONH2)2, and on top of that... was a fluffy ORANGE precipitate, the color of Fe3O4! The problem absolutely
must have to do with impurities in my denatured ethanol. My denatured ethanol contains: ethanol, methanol, toluene, benzene, ethyl acetate (I think),
and methyl butyl ketone (I think). I'll double check tomorrow on the contents. I thought it might be possible that there was a reaction between the
ketone and the (COOH)2. So, I began a follow-up experiment. I placed 10g of (COOH)2 in a flask; added 50mL CH3COCH3; and then added 5mL of 94% H2SO4.
Results of that experiment will be shared later today.
I weep at the sight of flaming acetic anhydride.
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madscientist
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On the subject of the follow-up experiment: the contents of the flask are now the color of orange soda. There is a small amount of a white powder on
the bottom of the flask. Maybe the following is occuring:
CH3COCH3 + (COOH)2 --(H2SO4)--> CH3C(COO)2CH3 + H2O
[Edited on 27-5-2002 by madscientist]
I weep at the sight of flaming acetic anhydride.
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madscientist
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Very interesting...
I poured the contents of the flask from the follow-up experiment into a 500mL beaker, and added 100mL of 10% NH4OH. There was a violent reaction; it
bubbled furiously for a few moments (the gas wasn't NH3, or I wouldn't have been able to continue breathing there), the contents of the beaker became
very hot, and a large amount of a white solid precipitated out.
I weep at the sight of flaming acetic anhydride.
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Polverone
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How bizarre
I must agree with you that paint-grade denatured alcohol is the source of your "orange soda." I prepared oxamide starting with 95% food grade ethanol
and had no problems. Of course this is a very expensive way to get such a simple chemical. Can you use 99% methanol instead when forming your ester? I
can get methanol (as "HEET" gas line de-icer) from the automotive supplies area at the local Safeway. The methanol works out to about $4.50 per liter,
which would be pretty bad on an industrial scale but is reasonable for the home chemist. The methanol has very little scent (to me), so be careful
that you aren't inundating yourself with methanol vapor if/when you try this route.
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madscientist
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I am now thinking that the white precipitate formed in the follow-up experiment is actually oxamide. The white precipitate is relatively insoluble in
water, and is slightly alkaline, as should be oxamide.
CH3COCH3 + (COOH)2 --(H2SO4)--> CH3C(COO)2CH3 + H2O
CH3C(COO)2CH3 + 2NH3 --> CH3C(OH)2CH3 + (CONH2)2
CH3C(OH)2CH3 --> CH3COCH3 + H2O
The violent boiling could easily be from the CH3COCH3 formed boiling off.
I prepared oxamide from methyl oxalate today. I placed 10g (COOH)2*2H2O in a beaker, then added 22.5g CH3OH. I poured in 4mL 94% H2SO4; there was a
bit of violent boiling for a few moments, and the contents of the beaker heated up considerably. I proceeded to heat the beaker to about 50C for an
hour. Then, I poured the contents of the beaker into 500mL of cold water. The methyl oxalate at first remained as a solid, but soon most either
dissolved or (more likely) decomposed. I quickly poured in 50mL of ammonia solution. After two minutes, I began filtering the contents of the beaker.
I ended up with 2.1g (CONH2)2.
I weep at the sight of flaming acetic anhydride.
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madscientist
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I tried preparing oxamide again today.
I placed 20.3g (COOH)2*2H2O in a flask. I added 34.3g CH3OH. Then, I added 5mL 94% H2SO4. I let it react for 24 hours. The next day, the flask
contained a solid mass, which was (COOCH3)2 (which melts at 54C). I shook the flask, causing the crystals to break up, forming a slush with the
unreacted CH3OH. I poured this into 150mL 10% NH4OH. A solid mass of (CONH2)2 formed quickly, and a lot of heat was evolved. I filtered out the
(CONH2)2, and accelerated the drying process by heating it gently. I ended up with 7.1g (CONH2)2.
I weep at the sight of flaming acetic anhydride.
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Madog
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STRANGE
i tried the acetone oxalate method and this is what hapened:
i added 40ml of acetone 10g of (COOH)2 and 5ml of H2SO4 to a beaker. the (COOH)2 disolved. 10 minutes later out of curiosity i droped a tiny amount
into some amonia, the amonia whent cloudy with a fine white precipitate. yay.. or so i thought. i let it sit and checked on it that night, it was a
darkish orange. the next mornign it was dark brown, and then after school it was darker and had crystals. some of the acetone had evaporated. i took
it and dumped it into some household NH3, nothing hapened but it was diluted to its oragned color. a little bit of something precipitated in about 5
minuted, it looked like it was oxalic acid, i added more NH3 and this stuff disolved, no bulbeing. the solution cleared up rapidly by adding more
amonia. then i had about half of this in a beaker and teste the PH, it was pretty acidic, hgm, added more amonia and it was filled with a fluffy off
white precipitate. i filtered this and washed it with water, it disolved, oh well, i guess the acetone oxalate method doesnt work.
the thing thats strange is the orange color, maybe your EtOH had some acetone in it, my CVS 70% ethanol has some. i guess ill get some methanol. my
hardware store ethanol clains to have 4% methanol and iddnt say anything else
Most people outgrow their pyro tendencies, we are the ones who\'s tendencies outgrew us.
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Madog
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ok, i did it again, i used denatured alcahol, which i believe to only have impureity of methanol, and i think i verified that. my brand is Sunnyside,
and it comes in a solvent can in the section of the hardware store that has all the solvents.
20ml of EtOH was added to 5 grams of oxalic acid and then i put in aproxomately 2.5ml of H2SO4. i swirled it around and let it sit, after a while all
the oxalic acid disolved. the next day, probaly 22 hours later i dumped it into some NH4OH solution and i got a white precipitate, i filtered it out
and dryed it, it is pretty insoluble in water and slightly basic(though i had alot of water and only a little oxamide the PH didnt seem to change much
but its definately not acidic)
the yield was just under a gram
i have another batch going now that is 2x the size of this one, i will report back when its done, i think im gona let this one go for a few days.
[Edited on 4/13/03 by Madog]
Most people outgrow their pyro tendencies, we are the ones who\'s tendencies outgrew us.
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MattEx
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Preparation of Oxamide (Ethane Diamide)
Anyone know a synthesis of this? I've searched for one at all my usual resources, but have been unable to find one. I have obtained the most
obvious reagent for it, Oxalic Acid (Ethanedioic acid), already. I just need to know how to amide it - I haven't studied chemistry at that level
quite yet  .
I need the oxamide as a burnrate modifier in my AP/PU rocket propellant compositions  .
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stygian
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Make ethyl oxalate and then add aqueous NH3.
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MattEx
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Oh, ok - thanks .
Pity I don't have any distillation equipment to make the dietyl oxalate with. It looks like i'll have to get some.. i've been meaning
to for quite awhile but it is very difficult to get, as no glassware suppliers where I live sell to individuals, and all purchases to businesses are
monitored  ...
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Magpie
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Can you buy glassware from eBay. I presume you have access to the US eBay market where there is a great deal of glassware for sale.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Eclectic
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You could try a melt of oxalic acid with urea (untested and unresearched idea).
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Odin
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| Quote: | Originally posted by Polverone
I must agree with you that paint-grade denatured alcohol is the source of your "orange soda." I prepared oxamide starting with 95% food
grade ethanol and had no problems. Of course this is a very expensive way to get such a simple chemical. Can you use 99% methanol instead when forming
your ester? I can get methanol (as "HEET" gas line de-icer) from the automotive supplies area at the local Safeway. The methanol works out
to about $4.50 per liter, which would be pretty bad on an industrial scale but is reasonable for the home chemist. The methanol has very little scent
(to me), so be careful that you aren't inundating yourself with methanol vapor if/when you try this route. |
You can get methyl hydrate at a Home Hardware Store as Windshield wiper fluid.
I think the percentage of methanol is over 70%.I dont think there are any additives added to prevent a simple distillation
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