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Author: Subject: Ethylacetoacetate...
vulture
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[*] posted on 14-6-2003 at 13:38
Ethylacetoacetate...


.....or 2-Ethyl-3-oxo-butyric acid.

1) To which class of organic compound does this compound belong? Keto-acids?
2) Does anybody have an idea about the synthesis?

ethylacetoacetate.gif - 1kB




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[*] posted on 14-6-2003 at 18:25


"Ethylacetoacetate" generally is used to refer to the ethyl ester of acetoacetic acid. :) I believe the compound you've targeted for synthesis is considered a keto acid.

What starting materials are you allowing yourself, and how involved of a synthesis are you looking for? You could prepare that compound via a Claisen condensation of a mix of ethyl acetate and ethyl n-butyrate. Ethyl n-butyrate could be prepared by Favorskii rearragement (in this case, treating 1-chlorobutan-2-one with sodium ethylate - you might have trouble preparing that from MEK, though, due to chlorination of MEK yielding lots of 3-chlorobutan-2-one - at least it's OTC, though) or from esterification of n-butyric acid (but you'd have to buy that from a chemical supply house).




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[*] posted on 15-6-2003 at 04:06


Ester? That's not an ester. There is no R-O-CO-R bond.



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[*] posted on 15-6-2003 at 08:22


Bugger, the structure I posted is incorrect. I obtained it by using the convert name to structure command of Chemsketch. No idea why it fucked up.:(

It's intended use is the Belousov-Zhabotinsky reaction, so the product should contain as less chloride as possible.

I was investigating if it was plausible to make it yourself from OTC compounds, but it seems not. If I have to buy the precursors I'd better buy the stuff itself because it's not expensive at all.

Ofcourse it would be fun to synthesize it myself..

[Edited on 15-6-2003 by vulture]




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[*] posted on 15-6-2003 at 09:24


You could make the required strong base by reaction of calcium oxide with anhydrous ethanol, making ethyl acetoacetate synthesis OTC (distill ethyl acetate out of nail polish remover).



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[*] posted on 11-12-2004 at 19:28


Most syntheses such as this which require anhydrous ethyl acetate call for drying it by refluxing with P2O5, however on Rhodium's ethyl acetoacetate synthesis, one purification method states that merely drying with granular CaCl2 overnight is sufficient. Is CaCl2 really enough? In that case why waste phosphorus pentoxide?



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[*] posted on 13-12-2004 at 15:47


Do you need to use the oxobutyric acid specifically? Every procedure I see on the net uses malonic or citric acid.

This site has a lot of pdf articles about cyclic reactions and lots of other interesting stuff about the general theme of chaos and complex systems.
Some of the articles concern the Belousov-Zhabotinsky directly.

http://chaos.ph.utexas.edu/entire.html#ChemicalInstabilities

[Edited on 13-12-2004 by alchemie]
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[*] posted on 14-2-2007 at 20:05
ethyl acetoacetate


I made some of this ester recently using the Claisen condensation of ethyl acetate using sodium ethoxide. It is interesting in that it requires elemental sodium as a reactant to make the sodium ethoxide in situ from generated ethanol. This depends on the charged ethyl acetate having a few percent of ethanol to get things started.

I started with 117mL of ethyl acetate and 9.25g of Na cut into slivers. This is refluxed for about 1.5 hours. A carmel colored solution results (color due to some tar generation apparently).

During the workup my procdure called for a wash with saturated aqueous NaCl. I misread this and used a saturated aqueous solution of CaCl2. What resulted was a 500mL separatory funnel nearly full of white gel! :o After feeling very discouraged for awhile I decided, what's to lose, I might as well try a salvage operation. So added enough water to get the gel to dissolve, separated off the water, then did a NaCl wash.

Final purification was by simple distillation into 3 cuts, with redistillation of the middle cut. The procedure said yields could be improved by vacuum distillation. My hydroaspirator seemed to lock onto about 63 mmHg absolute. So that is what I used and the final portion came over steadily at 95C. Normal bp for the ester is 181C.

My yield was 13mL, or 16.7%. As the procedure said only 6.5 mL would be expected by distilling at atmospheric pressure I was pleased.

This ester supposedly exists at 7% in its enolic form. This allows a qualitative test with ammoniacal CuSO4 that forms an aquamarine salt precipitate with the enol. This precipitate dissolves in chlorofrom. These tests on my ester were positive. Vogel also describes an interesting test with FeCl3 but I don't have any so couldn't do this.

This ester can supposedly be easily alkylated, hydrolyzed, and then decarboxylated to form various methyl ketones. I may try this with butyl methyl ketone being my most likely synthetic target.

[Edited on 15-2-2007 by Magpie]

[Edited on 15-2-2007 by Magpie]




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[*] posted on 15-2-2007 at 18:46


[Edited on 16-2-2007 by chemrox]
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[*] posted on 12-3-2009 at 20:48


Can methyl acetoacetate be produced by using magnesium methoxide which can be easily produced from dry methanol and magnesium powder? This would be a useful synthesis if it works because it would eliminate the need for expensive sodium metal. I chose the methyl ester because anhydrous methanol is readily available, along with ethyl acetate. You would end up with mixed esters, but this would not be a problem for synthesis of other compounds where the ester functional group is lost in the reaction.



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[*] posted on 13-3-2009 at 00:32


Magnesium methoxide is a substantially weaker base than sodium methoxide, particularly in nonpolar solvents, due to the higher acidity of the Mg<sup>2+</sup> cation when compared to Na<sup>+</sup>. But in principle it should work as long provided the reaction times are longer or conditions harsher. Try with a reflux of ethyl acetate in xylene with dried Mg(OMe)2 (or with the more soluble Mg(OEt)2), or some similar harsh conditions. Methanol (or ethanol) should be removed in the azeotrope and you should be left with the suspension of magnesium (m)ethyl acetoacetate salt.

But why not using NaOEt prepared from NaOH and EtOH? There are several methods for preparing NaOEt from NaOH and none is particularly difficult. See the threads on topic.




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