Oxime formation: practice and mechanism
Hydroxylamine (NH₂OH) reacts with aldehydes and ketones like a primary amine: after loss of water a C=N–OH group forms, an oxime.
Example
Hydroxylamine adds to the carbonyl group like a primary amine; after loss of water a C=N bond forms: an oxime. Oximes are usually crystalline and were used to identify aldehydes and ketones.
Mechanism step by step
- 1
The N of hydroxylamine (more nucleophilic than the O) attacks the carbonyl carbon.
- 2
After proton shifts a hemiaminal-like intermediate with C–OH forms.
- 3
Acid protonates the OH group and water leaves: C=N–OH (oxime).
Practice tasks
Which product forms, which reagent is needed? After each answer you see the explanation.
Which main product forms?
Typical mistakes
Often confused with: Imine formation · Reductive amination
Frequently asked questions
Why only catalytic acid?
Too much acid protonates the hydroxylamine and it is no longer a nucleophile. A weakly acidic pH (about 4 to 5) is ideal.
What can be done with oximes?
Beckmann rearrangement with acid to an amide (cyclohexanone oxime gives caprolactam for nylon-6) or reduction to the amine.