# Mechanism for the formation of butanoic acid from ethylacetoacetate

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.

• Formally, it looks like reversing a mixed Claisen ester condensation, followed by saponification. – Klaus-Dieter Warzecha Apr 8 '15 at 14:46
• 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. – RobChem Apr 8 '15 at 14:56

## 1 Answer

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

• Final arrow pointing towards me? Weird :D – Klaus-Dieter Warzecha Apr 8 '15 at 15:02
• Why not the hydroxide ion though? The hyroxide ion is used in the saponification. – RobChem Apr 8 '15 at 15:02
• Actually you're right: ethanolate is the stronger base! Hydroxide is correct and would explain the saponification step! – Klaus-Dieter Warzecha Apr 8 '15 at 15:06
• @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. – jerepierre Apr 8 '15 at 16:18