FireLion3
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What happens to the acyl group in a base-catalyzed deacetylation?
A base catalyzed deacetylation reaction can occur if an acyl group is conjugated or nearby other electron withdrawing groups, but I am struggling to
understand what happens to the acyl group?
If COCH3 is removed from the molecule, where does it go? Is it an ion in solution (doubt it)? A radical (doubt it)? Does it react with the base - this
I doubt to, since many deacetylation reactions describe using "dilute base", and call it catalyzed, meaning equimolar quantities are unlikely?
The acyl group is 2 hydrogen short of being acetaldehyde.... since it wont be gaining any hydrogen during base catalyzed deacetylation, then what
happens to it? Most reaction schemes I have seen only show the other desired substrates of a deacetylation but not the acyl group itself, or what
happens to it.
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Metacelsus
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It becomes a carboxylate ion.
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FireLion3
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How? A carboxylate ion has two oxygen (according to wiki). Acyl group only has one.
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DraconicAcid
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Acyl plus hydroxide gives an acetate ion, plus a hydrogen for what it used to be bonded to. That's my guess, at least.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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FireLion3
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Ah, that makes sense. So, the hydroxide is not used as a catalyst but as a reactant? Meaning calling it base catalyzed is an inaccurate statement?
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Dany
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Yes hydroxide ion in base hydrolysis of ester is not a catalyst because it is consumed during the reaction. The reaction of an ester with a base is
called saponification reaction. the reaction of HO- with and ester RCOOR' lead to the formation of carboxylate ion RCOO- and the corresponding alcohol
R'OH. however, the hydrolysis of an ester with acid (H3O+) is called acid catalyzed because the proton H+ is regenerated at the end of the
reaction. So for base hydrolysis we say "base promoted hydrolysis" and for acid we say "acid catalyzed hydrolysis".
Dany.
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