A compound 'C' (molecular formula, $$C_2H_4O_2$$) reacts with Na- metal to form a compound 'R' and evolves a gas which burns with a 'pop' sound. Compound 'C' on treatment with an alcohol 'A' in presence of an acid forms a sweet-smelling compound 'S' (molecular formula, $$C_3H_6O_2$$). On addition of NaOH to 'C', it also gives 'R' and water. 'S' on treatment with NaOH solution gives back 'R' and 'A'. Identify C, R, A, S and write down the reactions involved.