Hoffmann bromamide degradation :
RCONH2 + NaOH → RCONH− + Na+ + H2O
RCONH− + Br2 → RCONBr2 + Br−
RCONBr2 + NaOH → RCONBr− + Na+ + H2O
RCONBr− → RNCO + Br−
RNCO + H2O → RNHCOOH
RNHCOOH → RNH2 + CO2
Structures of N-bromoamide 2 and bromoamide anion 3 using symbols:
N-bromoamide 2: RCONBr2
Bromoamide anion 3: RCONBr−
i.e.
Hoffmann bromamide degradation : The amide is deprotonated by a base, such as sodium hydroxide, to form the amide anion.
The amide anion reacts with bromine to form the N-bromoamide.
The N-bromoamide is deprotonated by the base to form the bromoamide anion.
The bromoamide anion rearranges to form the isocyanate.
The isocyanate reacts with water to form the carbamic acid.
The carbamic acid decarboxylates to form the amine.
Structures of N-bromoamide 2 and bromoamide anion 3:
N-bromoamide 2 structure Opens in a new window
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N-bromoamide 2 structure
Note: The bromoamide anion is unstable and undergoes rearrangement to form the isocyanate.
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