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Difficulty: MediumAmines and Amides: Structure, Basicity, and Reactions

Primary aliphatic amines react with nitrous acid (HNO2HNO_2) at room temperature to yield an alcohol along with rapid effervescence. Which gas is evolved during this reaction?

  1. Nitrogen gas (N2N_2)Answer
  2. B
    Nitrogen(IV) oxide (NO2NO_2)
  3. C
    Ammonia gas (NH3NH_3)
  4. D
    Hydrogen gas (H2H_2)

Answer

Nitrogen gas (N2N_2)
Primary aliphatic amines react with cold nitrous acid (HNO2HNO_2) to form an unstable diazonium compound that decomposes rapidly at room temperature. This decomposition produces an alcohol, water, and liberates nitrogen gas (N2N_2), which is observed as effervescence.

Step-by-Step Solution

1
Identify the functional group and reagent
The reaction involves a primary aliphatic amine (R−NH2R-NH_2) and nitrous acid (HNO2HNO_2).
Nitrous acid is generated in situ from sodium trioxonitrate(III) (NaNO2NaNO_2) and dilute hydrochloric acid (HClHCl).
2
Write the chemical reaction equation
R−NH2+HNO2→R−OH+N2↑+H2OR-NH_2 + HNO_2 \rightarrow R-OH + N_2 \uparrow + H_2O
The aliphatic diazonium salt formed as an intermediate is highly unstable and decomposes immediately at room temperature.
3
Determine the gas released
The effervescence observed is due to the release of nitrogen gas (N2N_2).
Deamination of aliphatic primary amines yields nitrogen gas as the characteristic gaseous product.

Key Concept

Reaction of primary aliphatic amines with nitrous acid to yield alcohols and nitrogen gas
Estimated Time:1m 0s
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Topics

Amines and Amides: Structure, Basicity, and Reactions

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