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Topic: Mechanism behind carboxylic acid + alchohol, ester condensation  (Read 6175 times)

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Offline grkn

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Mechanism behind carboxylic acid + alchohol, ester condensation
« on: September 07, 2007, 03:12:05 PM »


Is this on the right track? What role has sulfuric acid?
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Offline Yggdrasil

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Re: Mechanism behind carboxylic acid + alchohol, ester condensation
« Reply #1 on: September 07, 2007, 04:06:22 PM »
Methyl carbocations do not exist!!!

In the presence of a strong acid, like sulfuric acid, can you think of what might be protonated in solution?
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Offline grkn

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Re: Mechanism behind carboxylic acid + alchohol, ester condensation
« Reply #2 on: September 07, 2007, 08:36:58 PM »
The doubly bonded oxygen perhaps :)
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Offline Yggdrasil

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Re: Mechanism behind carboxylic acid + alchohol, ester condensation
« Reply #3 on: September 07, 2007, 09:35:09 PM »
Yup.  Now draw the resonance structures of the protonated carbonyl.
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Offline grkn

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Re: Mechanism behind carboxylic acid + alchohol, ester condensation
« Reply #4 on: September 08, 2007, 09:35:59 AM »

Better?
« Last Edit: September 08, 2007, 12:40:57 PM by grkn »
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Offline osamarashad

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Re: Mechanism behind carboxylic acid + alchohol, ester condensation
« Reply #5 on: September 08, 2007, 11:53:36 AM »
the role of H2SO4 to absorb H2O and make the reaction in one way
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Offline Yggdrasil

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Re: Mechanism behind carboxylic acid + alchohol, ester condensation
« Reply #6 on: September 08, 2007, 12:50:36 PM »
In addition to helping remove water, the sulfuric acid acts as a catalyst.  It protonates the carbonyl oxygen increasing the electrophilicity of the carbonyl carbon.  This makes the carbonyl carbon more succeptible to nucleophilic attack by the methanol.
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