An organic compound A (molecular formula C₂H₄O₂) reacts with Na metal to form a compound B and evolves a gas which burns with a pop sound. Compound A on treatment with an alcohol C in the presence of a little of concentrated sulphuric acid forms a sweet-smelling compound D (molecular formula C₃H₆O₂). Compound D on treatment with NaOH solution gives back B and C. Identify A, B, C and D.

The organic compound, A, with the molecular formula C₂H₄O₂ is ethanoic acid (CH₃COOH), as it evolves hydrogen with a pop sound on reacting with sodium.

When ethanoic acid reacts with sodium, a compound B called the sodium ethanoate (CH₃COONa) is formed.

The alcohol, C, is methanol (CH₃OH) which is treated with ethanoic acid in the presence of concentrated sulphuric acid to form a compound D.

The sweet-smelling compound D is methyl ethanoate (CH₃COOCH₃).

The chemical equation for the above stated reaction is as follows:
CH₃OH + CH₃COOH → CH₃COOCH₃ + H₂O

When ethanoic acid reacts with alcohol in the presence of concentrated sulphuric acid, a sweet-smelling cmpound, ester is formed. Methyl ethanoate is a carboxylate ester, which on reaction with sodium hydroxide gives back methanol and Sodium ethanoate.

The chemical equation is as follows:
CH₃COOCH₃ + NaOH → CH₃COONa + CH₃OH