So, I came across a quite versatile method to synthesize aldehydes and ketones, its called the Acetoacetic ester synthesis.

Suppose I need some 2-pentanone. So to synthesize it via this method I can do this

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But I'm more worried about adding a base to Acetoacetic ester. Won't self condensation occur between two molecules of Acetoacetic ester like this?

enter image description here

If it occurs how do we minimize it? If it doesn't then why?

Any help will be appreciated.

  • $\begingroup$ Doesn't happen. You just get proton exchange. $\endgroup$ – user55119 Jan 27 '19 at 17:09
  • $\begingroup$ Can you tell me the reason, please? $\endgroup$ – Shivansh J Jan 27 '19 at 17:19
  • $\begingroup$ If the addition occurred at all AAE anion would prefer the ketone, a reaction that forms an intermediate alkoxide, whose conjugate acid has pKa ~15-18. The pKa of AAE is ~11. Seems to be an uphill battle. $\endgroup$ – user55119 Jan 27 '19 at 17:27
  • $\begingroup$ @user55119 But I've learned that addition to ketones would require special conditions (i.e addition to ketones is mostly unfavourable due to steric hinderence). $\endgroup$ – Shivansh J Jan 27 '19 at 18:41
  • $\begingroup$ I disagree. Addition of what to ketones? Grignard reagents? Stobbe condensation? Wittig reaction? $\endgroup$ – user55119 Jan 27 '19 at 18:49

Self-condensation is typically not an issue with 1,3-dicarbonyl compounds, such as the one in your question. Why? Due to their acidity ($\mathrm{p}K_\mathrm{a}$ around 9 to 11), most 1,3-dicarbonyls exist in their enolate form in solution. Therefore, there is very little of the original electrophilic 1,3-dicarbonyl which the enolate can attack. Hence, the amount of self-condensation taking place is relatively little and usually not a concern.


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