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SolutionsReduction

1. Which amine is obtained?

  1. CH3CH2CH2C≡N + LiAlH4, then H2O
  2. CH3CONHCH2CH3 + LiAlH4, then H2O
  3. Cyclohexanone + CH3NH2, NaBH3CN
  4. Nitrobenzene + Fe/HCl, then NaOH
  1. Butylamine, CH3CH2CH2CH2NH2 (a primary amine with one carbon more than the halide from which the nitrile was made).
  2. N-Ethylethylamine (diethylamine): LiAlH4 reduces the C=O of the amide to CH2.
  3. N-Methylcyclohexylamine (reductive amination).
  4. Aniline.

2. Reductive amination

Which carbonyl compound and which amine would you use to prepare N,N-dimethylbenzylamine by reductive amination? And 2-butylamine?

Benzaldehyde and dimethylamine for the first; butanone and ammonia for the second.

NaBH3CN reduces the iminium ion much faster than the carbonyl compound, so it can be added from the start.

3. Oxidation state

Why can amides, nitriles and nitro compounds be reduced to amines, while amines cannot be reduced further?

Because in the amine the nitrogen already has its minimum oxidation state (−3) and the carbon bonded to it cannot be reduced without breaking the C–N bond. In the other functions the carbon or the nitrogen is more oxidized.

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