ItalianChemist
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oxalyl chloride and water
A few time ago I put oxalyl chloride in not anhydrous solvent.
A lot of withe smoke appeared, i think it was hydrogen chloride, but is possible that carbon monoxide was evolved?
The reaction is:
(COCl)2+H2O -> 2HCl+CO2+CO
or
(COCl)2+2H2O -> 2HCl + (COOH)2?
Thanks!
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redox
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It is the seconds reaction. Acid chlorides hydrozyle to the acid and HCL.
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Ozone
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Yes, oxalic acid and HCl.
O3
[Edit]:
Hmm. It would appear that in some cases (depending upon pH and temperature) quenching oxalyl chloride may yield either CO + CO2 + 2HCl or oxalic acid
+ 2HCl. I suppose this might be due to a kinetic limitation where hydrolysis competes with elimination of Cl- at the expense of the C-C bond?
Fieser and Fieser point out the rxn with other carboxylic acids (and alcohols) to yield ROCl or RCl (respectively) when heated with a trace of alkali.
Chem. Res. Toxicol., 2002, 15 (8), pp 1096–1105 points to the direct formation of CO + CO2, but to oxalic acid via oxalylphosphate in neutral
phosphate buffer.
More superficial sources such as inchem (IIRC) and soe MSDS indicate oxalic acid and HCl.
It also seems that water into oxalyl chloride vs. oxalyl chloride into excess water may have different results, as well.
I suppose there is only one thing to do...I'll quench some oxalyl chloride into a large excess of water and use the HPLC to look for (and perform
rough quantitation of) oxalic acid. I'm running organic acids (BioRad Aminex HPX-87H, ABS @ 210nm) on monday, anyway, so that shouldn't be too hard to
squeeze in. I'll post the results here.
Cheers,
O3
[Edited on 9-4-2011 by Ozone]
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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garage chemist
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Oxalyl chloride does not give any oxalic acid upon hydrolysis because the monochloride intermediate is highly unstable and immediately decomposes to
HCl, CO2 and CO.
So CO, CO2 and HCl are the only products.
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jon
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i was always curious with my dumb self why in the hell you could use acid chlorides under aqueous conditions in a reaction known as the
Schotten-Baumann reaction it's somewhat counterintuitive.
http://www.organic-chemistry.org/namedreactions/schotten-bau...
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ItalianChemist
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Thanks Ozono, let me know the results!
Isn't used anhydrous dichloromethane in the Shotten-Baumann?
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ScienceSquirrel
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The acid chloride does undergo hydrolysis as a competing reaction but the amine is a more effective nucleophile than water or hydroxide so it reacts
at a faster rate. The other factor favouring it is that the mixture is biphasic eg the amine, acid chloride and amide are in one phase and the alkali
hydroxide is in a separate aqueous phase. The amine hydrochoride reacts at the boundary between the phases to reform the amine and an alkali chloride.
Organic chemistry is very recipe based as getting a good set of reaction conditions can mean the difference between a stonking yield and brown glop.
[Edited on 10-4-2011 by ScienceSquirrel]
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woelen
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I can confirm garage chemists post. I actually tried it and indeed, no oxalic acid is formed. This is an exception to the rule that in general acyl
chlorides give the acid and hydrochloric acid when treated with water.
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Ozone
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OK, I have confirmed garage chemist and woelen:
Method:
To 50 mL just-freezing DI water was rapidly added 1 mL chilled oxalyl chloride (5°C, 98%) with rigorous magnetic stirring. After vigorous
effervescence, the mixture was degassed under vacuum with sonication, quantitatively transferred to a 100 mL volumetric flask and brought to mark with
18 Mohm Di water. This solution was chromatographed using an Agilent 1100 HPLC, a DAD monitoring 210 nm, BioRad Aminex HPX-87H/H2SO4 0.005N/0.8
mL/min. The instrument was standardized against a 3 pt curve (250, 500, 1000 ppm) and the detection limit was easily 10 ppm) of oxalic acid
(calculated from sodium oxalate).
Result:
No oxalic acid was noted above the detection limit. A new peak (and shoulder) which eluted earlier was noted (and remains unidentified).
Conclusion:
Under these conditions, oxalyl chloride quantitatively yields something other than oxalic acid. It is likely that the products are CO2 and CO (and,
undoubtedly, HCl; the solution was strongly acidic after the rxn). Another product (or two) may result (perhaps as transient species) or may be part
of the 2% impurity declared on the material label.
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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ItalianChemist
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Thanks Ozono!
The other products are phosgene and tricloroacetyl chloride isn't it?
Wow! You have 100g of (COCl)2, I have only 25ml 
Bye
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woelen
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Good to see what you have done Ozone. In my experiment I simply allowed the mix to react and stand for a while and then heated the mix slowly and
carefully. No solid material remained after that, only some white stains on glass as if tap water is evaporated. Probably that is due to impurity of
the reactants I used.
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