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I'd read yesterday that Grignard reagents can't give ketones on reaction with carboxylic acids. It is because of the fact that Grignard reagent is a "super-base", and it will deprotonate the acid to form a carboxylate salt, rather than doing a $\ce{Nu-}$ attack.

However, after watching a video on Youtube, on the reaction of organolithium with acids (example reaction below),

organolithium-with-acids-mechanism

I wondered,

  • After the acid-base reaction, why couldn't Grignard reagent (when taken in excess) do a $\ce{Nu-}$ attack on the carboxylate salt, just like organolithium does and then form ketone? Just like it does with an ester, acid chloride, etc.
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  • $\begingroup$ Does this answer your question? Why are organolithium and organomagnesium compounds nucleophilic in nature? $\endgroup$ Aug 29 '20 at 7:44
  • $\begingroup$ @Safdar, No. I couldn't think how a difference in Nu nature can prevent the grignard reagent from attacking the carboxylate salt? $\endgroup$ Aug 29 '20 at 7:53
  • $\begingroup$ After formation of salt, the $\ce{O-}$ makes carbon way less electrophilic due to the distribution of electron density, so we need a much better nucleophile. $\endgroup$ Aug 29 '20 at 7:56

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