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chemrox
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I'd like to see a TCT method for oxalyl chloride. I'm running two methods of dehydrating the oxalic dihydrate:
13.75 g of oxalic acid dihydrate were place in a rb with 200 ml of toluene. A dean-stark was incorporated in the setup. The mixture was refluxed for
about 1.5 hours during which time 3.9 ml water was collected. The solvent was removed by rotovap.
10 g of oxalic acid dihydrate was place in small porcelain dish and placed in the vacuum oven. Will be tried again.. takes a lot more time than the
above.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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Paddywhacker
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Be advised that dehydrating with H<sub>2</sub>SO<sub>4</sub> is a process that could end in tragedy. The mixture releases
carbon monoxide and carbon dioxide. A single whiff of high-strength carbon monoxide is all it takes to end your life.
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Waffles SS
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What about drying Oxalic acid by molecular sieve (3A prefer)in Alcohol(like EtOH)as solvent?
[Edited on 7-2-2014 by Waffles SS]
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chemrox
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The purpose of this post is following up on the dehydration methods I posted. Heating the acid in refluxing toluene resulted in considerable
sublimation loss. Heating in open oil bath at 90-110 resulted in incomplete dehydration but seemed better than heating at 80 in the vacuum oven @
30". The latter messed the oven up and I will have to change the pump oil. Incomplete dehydration. I'm going to use the process indicated at the
beginning of this thread.
One more thing: there was almost no acid in the toluene. Not worth flashing.
[Edited on 16-2-2014 by chemrox]
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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S.C. Wack
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In the thread on this started a few weeks before this one, I noted how this was not a problem. Not at all really, it was without reflux, straight hard
distillation, stopping for addition and shaking to break up the clumping now and then. The biggest problem is vacuuming off the toluene. Not saying to
try it, or sure why a Dean-Stark would not work the same; just defending toluene.
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kmno4
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OMG
How simple things can be complicated .....
I have needed recently some ahyd. oxalic acid for some experiments with direct esterification of phenol.
One more time it turns out that the simplest method dehydration is drying of dihydrate on hot plate in air to costant weight. The mass loss is
continuous process, without monohydrate stage. At the end of dehydration, weight of the acid remains almost constant, with small decrease caused by
sublimation. At ~60 C this loss is smaller than 0,1g from 10g sample (during ~12 h, counting from the end of dehydration).
Literature searching, by the way, gave me old paper from 1907 year. Author dehydrates oxalic acid just in this simple way and use it for very precise
masurements of decomposition of oxalic acid in sulfuric acid, where water is very important factor (DOI: 10.1021/j150084a003).
I also tried azeotropic dehydration with benzene, rater for fun than preparative purposes. Surprisingly slow reaction, with grams amouts of oxalic
acid in D-S trap after few hours refluxing.
Just wasting the time.
Слава Україні !
Героям слава !
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chemrox
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@Sauron: as for scale I would be very interested in the yield of these larger quantities. I also thought you had a TCT method (?) For those of you
that don't have a rotovap pm me; I can set you up. I'm trying to find one of those older Kugelrohrs. There are some homebakes for 25ml samples...
[Edited on 25-2-2014 by chemrox]
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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