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Michael Wallis Adkins

Reaction of primary amine with mixed acid anhydride

Chris Johnston  Follow

The reaction between anhydride and primary amine is by the Nucleophic addition-elimination mechanism (NOT by SN2).

First step: Nucleophilic addition step (Rate determining step):

The addition of amine to carbonyl center (at the most electrophilic carbonyl center and it should generate least sterically hindered intermediate) gives rise to a tetrahedral intermediate (4 groups bonded to the carbon center), which is influenced by steric hinderance. Therefore the attack of primary amine will prominently take place at -CH3 end carbonyl center which is more electrophilic and gives less sterically hindered intermediate.

Second step: Elimination step (fast step, not a rate determining):

The internal nucleophile (O- of earlier carbonyl) reverts back to generate the carbonyl center and propionate ion is eliminated.

Note: As the mechanism of reaction is not by SN2, therefore leaving group stability is not the sole criteria.

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Erik Bergstr?m  Follow
kinetic propertyMore
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Jimswen  Follow
Theres no such thing as a "sterically hindered intermediate". Steric hindrance is a More
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Iain Mcgregor  Follow
Then "sterically hindered transition state or pathway" will be correct ?More
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Evelyn Dellcerro  Follow
thermodynamic propertyMore
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Jona Arkenson  Follow
of a molecule.More
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