To propose a mechanism for an Î±-hydroxy amide is treated with Br 2 in aqueous NaOH under Hofmman rearrangement conditions.

Question

When an α-hydroxy amide is treated with Br2 in aqueous NaOH under Hofmann rearrangement conditions, loss of CO2 occurs and a chain-shortened aldehyde is formed. The mechanism involves the following steps: Base abstracts an acidic amide proton, yielding amide anion 1; The amide anion reacts with bromine in an α-substitution reaction to give N-bromoamide 2. Abstraction of the remaining amide proton by base gives a resonance-stabilized bromoamide anion 3; Rearrangement occurs to yield isocyanate 4; Water adds to the isocyanate to yield carbamic acid 5; Elimination of CO2 yields carbinolamine 6; Following proton transfer, expulsion of ammonia yields the final product aldehyde. Write out the mechanism and then draw the structures of bromoamide anion 3 and amide anion 1.

Answer 1

Question

Chapter 24.SE, Problem 43MP

Interpretation Introduction

Interpretation:

To propose a mechanism for an Î±-hydroxy amide is treated with Br₂ in aqueous NaOH under Hofmman rearrangement conditions.

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When an α-hydroxy amide is treated with Br2 in aqueous NaOH under Hofmann rearrangement conditions, loss of CO2 occurs and a chain-shortened aldehyde is formed. The mechanism involves the following steps: Base abstracts an acidic amide proton, yielding amide anion 1; The amide anion reacts with bromine in an α-substitution reaction to give N-bromoamide 2. Abstraction of the remaining amide proton by base gives a resonance-stabilized bromoamide anion 3; Rearrangement occurs to yield isocyanate 4; Water adds to the isocyanate to yield carbamic acid 5; Elimination of CO2 yields carbinolamine 6; Following proton transfer, expulsion of ammonia yields the final product aldehyde. Write out the mechanism and then draw the structures of bromoamide anion 3 and amide anion 1.

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