Question

An organic compound (A) with molecular formula C₂H₇N reacts with nitrous acid to form compound (B) which is unstable. Hence compound (B) gets converted to compound (C). Compound (C) is used as a substitute for petrol. Identify compounds (A), (B) and (C).

Hint:

While aliphatic diazonium salts are unstable and turn into alcohols, aromatic diazonium salts (like benzenediazonium chloride) are relatively stable at cold temperatures (0-5C) and are vital intermediates in synthetic organic chemistry.

Answer 1

Concept: Primary aliphatic amines react with nitrous acid (HNO₂) to form highly unstable aliphatic diazonium salts. These salts immediately decompose to release nitrogen gas and form alcohols.
The molecular formula C₂H₇N corresponds to Ethylamine (CH₃CH₂NH₂). It is a primary aliphatic amine.
When ethylamine (A) reacts with nitrous acid (prepared in situ from NaNO₂ + HCl) at low temperatures, it forms an unstable diazonium salt. • Compound (B): Ethyldiazonium chloride (CH₃CH₂N₂^+Cl^-). This compound is extremely unstable and cannot be isolated.
The unstable diazonium salt (B) reacts with water (formed during the reaction) to produce an alcohol while evolving nitrogen gas. • Compound (C): Ethanol (CH₃CH₂OH). Ethanol is widely used as a "bio-fuel" or a substitute/additive for petrol (often called Power Alcohol). Chemical Reactions:
(A)CH₃CH₂NH₂ + HNO₂ + HCl 273-278 K (B, unstable)[CH₃CH₂N₂^+Cl^-] + 2H₂O (B)[CH₃CH₂N₂^+Cl^-] + H₂O (C)CH₃CH₂OH + N₂ + HCl [h] |c|l|l| Code & Name & Formula
(A) & Ethylamine (Ethanamine) & C₂H₅NH₂
(B) & Ethyldiazonium chloride & C₂H₅N₂^+Cl^-
(C) & Ethanol (Ethyl alcohol) & C₂H₅OH