| Step 1: An acid/base reaction. Since we only have a weak nucleophile and a poor electrophile we need to activate the ester. Protonation of the amide carbonyl makes it more electrophilic. |
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| Step 2: The water O functions as the nucleophile attacking the electrophilic C in the C=O, with the electrons moving towards the oxonium ion, creating the tetrahedral intermediate. |
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| Step 3: An acid/base reaction. Deprotonate the oxygen that came from the water molecule. |
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| Step 4: An acid/base reaction. Need to make the -NH2 leave, but need to convert it into a good leaving group first by protonation. |
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| Step 5: Use the electrons of an adjacent oxygen to help "push out" the leaving group, a neutral ammonia molecule. |
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| Step 6: An acid/base reaction. Deprotonation of the oxonium ion reveals the carbonyl in the carboxylic acid product and regenerates the acid catalyst. |
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The above reaction under acidic conditions:
- Note that the acid catalysed mechanism is analogous to the acid catalysed hydrolysis of esters.
- The mechanism shown below proceeds via protonation of the carbonyl not the amide N (see step 1).
- The mechanism is an example of the less reactive system type.
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