A hydrocarbon ‘A’, (C 4 H 8 ) on reaction with HCl gives a compound ‘B’, (C 4 H 9 Cl), which on reaction with 1 mol of NH 3 gives compound ‘C’, (C 4 H 11 N). On reacting with NaNO 2 and HCl followed by treatment with water, compound ‘C’ yields an optically active alcohol, ‘D’. Ozonolysis of ‘A’ gives 2 mols of acetaldehyde. Identify compounds ‘A’ and ‘B’.