Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Nozon on August 08, 2019, 12:24:22 PM
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This may be theoretical and unknown but I am wondering how LiAlH4 exactly reacts with an amide.
My book refers it as a hydrid ion makes an nucleophilic attack on the alpha-carbon, forcing the pi-bound of Oxygen to go up to itself and makes an negative charge and then Al is steps in and bind oxygen, making it a good leaving group, so that nitrogen can make a pi-bound to the alpha-carbon and become a cation. (Iminium Ion).
A new nucleophilic attack by a hydrid ion from a new LiAlH4 removes the pi bound between N and C and neutralize the molecule into an amine.
My question is here, what is the positively charged lithium's role? I would I be wrong to assume it destabilize the oxygen's pi-bound (due to it negative polarity) to the alpha carbon at first, so a nucleophilic attack can occur?
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I think you can reduce an amide with AlH3, its the hydride and aluminum that is important, lithium not so much.
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Rolnor - okay thanks a lot.
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Lithium usually coordinates to the carbonyl oxygen and furhter activates it for the reduction. It plays some role because changing the counterions effects the reactivity of the reducing agent.