Hi. So we did the Cannizzaro rxn with 4-chlorobenzaldehyde to make 4-chlorobenzoic acid and 4-chlorobenzyl alcohol. We carried it out with 11M KOH. I understand the mechanism and I am assuming that because this is a strong basic solution, it forms that doubly charged anion as an intermediate. I just have a few questions about the extraction process. Why were the two initial products formed the carboxylate ion and the alcohol? Why was the alcohol protonated?? To separate the layers, we added water first and then CH2Cl2.
BTW methanol was used as a solvent. WHY WAS THE ALCOHOL NOT AN ALKOXIDE AFTER BEING FORMED?!?
BTW methanol was used as a solvent. WHY WAS THE ALCOHOL NOT AN ALKOXIDE AFTER BEING FORMED?!?
-
Okay, here goes...
Before acidic workup, the alkoxide O minus is much less stable than the carboxylate (which is stabilized by resonance), so it would be protonated first by the MeOH or water.
You really can't avoid workup, bc you must have water for the KOH to be in solution, and you have methanol either way, and either one can account for the acidic workup.
Phenol is much more acdic than benzylalcohol b/c the conj. base of phenol is stabilized by resonance with the aromatic ring. Benzylalcohol has no such luxury and give high localized electron density on the O. This means that since the conj. base is less stable, it would be protonated first.
In many cases, ppl downplay the stability of the carboxylate anion, but it is quite stable.
Hope this helps...
Before acidic workup, the alkoxide O minus is much less stable than the carboxylate (which is stabilized by resonance), so it would be protonated first by the MeOH or water.
You really can't avoid workup, bc you must have water for the KOH to be in solution, and you have methanol either way, and either one can account for the acidic workup.
Phenol is much more acdic than benzylalcohol b/c the conj. base of phenol is stabilized by resonance with the aromatic ring. Benzylalcohol has no such luxury and give high localized electron density on the O. This means that since the conj. base is less stable, it would be protonated first.
In many cases, ppl downplay the stability of the carboxylate anion, but it is quite stable.
Hope this helps...