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Reductions of Carboxylic Acids and Esters

reduction of carboxylic acids using LiAlH4

reduction of carboxylic acids using LiAlH4
Reactions usually in Et2O or THF followed by H3O+ work-ups
Reaction type:  Nucleophilic Acyl Substiution then Nucleophilic Addition

Summary

Related Reactions
REACTION OF LiAlH4 WITH AN ESTER

Step 1:
The nucleophilic H from the hydride reagent adds to the electrophilic C in the polar carbonyl group of the ester. Electrons from the C=O move to the electronegative O creating an intermediate metal alkoxide complex.
reduction of an ester using hydride
Step 2:
The tetrahedral intermediate collapses and displaces the alcohol portion of the ester as a leaving group, this produces a ketone as an intermediate.
Step 3: 
Now we are reducing an aldehyde.
The nucleophilic H from the hydride reagent adds to the electrophilic C in the polar carbonyl group of the aldehyde. Electrons from the C=O move to the electronegative O creating an intermediate metal alkoxide complex. 
Step 4:
This is the  work-up step, a simple acid/base reaction. Protonation of the alkoxide oxygen creates the primary alcohol product from the intermediate complex.

 


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© Dr. Ian Hunt, Department of Chemistry, University of Calgary