An organic compound 'A' on treatment with NH3 gives 'B', which on heating gives 'C'. 'C', when treated with Br2 in the presence of KOH produces ethylamine. Compound 'A' is:

The compound A is propionic acid CH3CH2COOH. Propionic acid reacts with ammonia to form ammonium propionate. On heating, ammonium propionate is converted to propionamide. Hoffmann bromamide reaction in presence of KOH and bromine converts propionamide to ethyl amine. In this process, one carbon atom is lost.
CH3−CH2−COOH + NH3 → CH3−CH2−COO⁻ + NH4⁺
Δ → CH3−CH2−CONH2
KOH + Br2 → CH3−CH2−NH2
(A) (B) (C)