Monoamine
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Separating chloroacetic acid and an sulfuric acid
I'm trying out the method from this patent for making chloroacetic acid from trichloroethylene by oxydizing it with sulfuric acid.
According to the patent this works very well. However, I'm having a lot of trouble separating the two later on.
To test their solubility, I tried DCM, dichloroethane, hexane and toluene. The thing is that the sulfuric acid does not seem to be soluble in
any of these solvents - and neither does the chloroacetic acid!
So how am I supposed to separate them now, other than distillation (which I would like to avoid since that would likely damage the product or the
sulfuric acid might react with the chloroacetic acid.
Does anybody know a likely solvent system that I can use to separate these two compounds?
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Boffis
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@Monoamine, the patent suggest extraction with ether so I presume you don't have access to this solvent. Maybe some other polar solvent like an alkyl
acetate, or another ether say THF or dioxane (these might be too soluble in the aqueous medium) or diglyme (dimethylglycol / dimethoxyethane)
Alternatively could you add an alcohol and esterify it then distil the ester out of the sulphuric acid?
Alternatively could you treat with excess calcium carbonate, filter off the gypsum and isolate the calcium salt? Liberating it from the calcium salt
may be tricky but it depends what you want to do with it. Quite a few operations with chloroacetic acid use the sodium salt anyway so you may be able
to substitute the calcium salt. If not you could treat the calcium salt with sodium carbonate to get the sodium salt.
For me the methyl or ethyl ester would be most useful so I would probably go for the ester route.
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DraconicAcid
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Trying to extract with an ester will probably result in the acid hydrolyzing the solvent.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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bnull
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The same patent (US1304108) suggests:
vacuum distillation (p.1, lines 58-62);
use of a gas current (p.2, lines 1-5);
solvent extraction (p. 2, lines 6-9);
esterification (p.2, lines 10-17).
The way to go is either vacuum distillation or esterification. I'd go with vacuum distillation because the distillate wouldn't require more processing
(apart from desiccation). The solvent extraction may work with solvents other than ether with varying degrees of success. Forget the gas current; it
is more trouble than it is worth.
From Ullmann's (page 3 of attachment): | Quote: | 2.3.1. Hydrolysis of Trichloroethylene[13–15]
Equal amounts of trichloroethylene and 75 % sulfuric acid are reacted at 130--140 °C in a continuous process so that with complete trichloroethylene
conversion, the resultant reaction mixture contains about 50 % chloroacetic acid and 1--2 % water. This blend is vacuum distilled to give pure
chloroacetic acid. During this process the vapors are washed with water, which is returned to the sulfuric acid as a diluent. |
Attachment: 3527334777_c01.pdf (345kB)
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Quod scripsi, scripsi.
B. N. Ull
P.S.: Did you know that we have a Library?
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clearly_not_atara
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Depending on how much sulfuric acid you used, it might be possible to absorb it onto anhydrous sodium sulfate along with any water and then filter off
chloroacetic acid.
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Monoamine
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Thanks for the replies. I will try it with ether then. But distillation also seems like a good option.
But keep in mind: the reaction calls for 4 times as much sulfuric acid as acetic acid, so there is quite a lot.
Also, Im slightly worried that the sulfuric acid will cleave the ether.
But it's certainly worth a go!
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bnull
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What did you do with all the hydrogen chloride generated?
Quod scripsi, scripsi.
B. N. Ull
P.S.: Did you know that we have a Library?
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