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My problem sheet asks me: "Draw a mechanism for the formation of $\ce{EtCH2COOH}$ from the reaction of $\ce{MeCOCH(Et)COOEt}$ with $\ce{NaOH}$ in $\ce{EtOH}$"

This has got me stumped. The mechanisms that I have attempted use the hydroxide ion as the base/nucleophile, is this right? My initial thoughts were to make the enolate by deprotonating between the caronyl groups then doing and aldol into the ketone part of another molecule of ethylacetoacetate but this just gives me a complicated molecule that I can't see reacting further.

I simply cannot find a way to make the product using only the reactants in the question.

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    $\begingroup$ Formally, it looks like reversing a mixed Claisen ester condensation, followed by saponification. $\endgroup$ Apr 8, 2015 at 14:46
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    $\begingroup$ Thank you very much. Should I use the hydroxide ion as the nucleophile or should I use the ethoxide ion? Given that sodium hydroxide is dissolved in ethanol. $\endgroup$
    – RobChem
    Apr 8, 2015 at 14:56

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I thought about adding solid $\ce{NaOH}$ to ethanol and therefore used $\ce{EtO-}$ ;) :

enter image description here

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  • $\begingroup$ Final arrow pointing towards me? Weird :D $\endgroup$ Apr 8, 2015 at 15:02
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    $\begingroup$ Why not the hydroxide ion though? The hyroxide ion is used in the saponification. $\endgroup$
    – RobChem
    Apr 8, 2015 at 15:02
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    $\begingroup$ Actually you're right: ethanolate is the stronger base! Hydroxide is correct and would explain the saponification step! $\endgroup$ Apr 8, 2015 at 15:06
  • $\begingroup$ @RobChem It doesn't matter which (hydroxide or ethoxide) you use to initiate the retro-Claisen. If the ethoxide participates, then hydroxide will saponify the resulting ester. $\endgroup$
    – jerepierre
    Apr 8, 2015 at 16:18
  • $\begingroup$ I have one concern about this approach. How much of the substrate is protonated. The enolate will not cleave. This may only be a rate problem. Another route is to do an acid hydrolysis/decarboxylation followed by a haloform reaction. $\endgroup$
    – user55119
    Sep 20, 2021 at 20:09

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