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-I Have 2 problems I followed a method but one of them a low yield and the other didn't precipitate(give red liquid) -I used ethanol instead of methanol but it worked with one and the other didn't although the first reaction didn't ppt but its color changed into red like the other reaction that ppt. so I wonder why it doesn't ppt. and the other didn't give a moderate yield -I tried to add diethyl ether to the first reaction product but nothing happened

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    $\begingroup$ Welcome to ChemSE. Have you monitored the formation of the Schiff's base? IR or NMR. There is a chance that the EtOH is wet. I would opt for toluene azeotrope with a Dean-Stark trap or a Soxhlet with 3 Angstrom molecular sieves. If that fails, use a weak acid catalyst such as benzoic acid. Removal of water is essential. $\endgroup$
    – user55119
    Sep 14 at 23:35
  • $\begingroup$ is this SPECIFIC reaction well known in the literature? that keto carbon doesn't look particularly reactive to me—Schiff base reactions start with nucleophilic attack of the amine on the keto carbon. My guess is that this is why the reactions aren't working. The reason the bottom reaction has any yield at all (if i had to guess) is hydrogen bonding between the amine and the N-heterocyclic nitrogen of the aldehyde directing the amine lone-pair towards the keto carbon, catalyzing the reaction but not impacting its energetics. just my guess, though. $\endgroup$ Sep 15 at 6:38


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