COMEDK202510 May 2025Evening ShiftChemistryHydrocarbonsActual
Identify the reagents to be used to complete the given reaction.
Options
- A( A = HBr B = ) alc. ( KOH C = CaC ₂ D = ) Red hot Ni tube
- B( A = Br ₂ / CCl ₄ ~B = ) aq. ( KOH C = ) Conc. ( H ₂ SO ₄ D = ) Red hot Cu tube
- C( A = CHBr ₃ ~B = ) aq. ( KOH C = ) Conc. ( HI D = ) Red hot Pd tube
- D( A = Br ₂ / CCl ₄ ~B = ) alc. ( KOH C = NaNH ₂ D = ) Red hot Fe tube
Correct answer
D. ( A = Br ₂ / CCl ₄ ~B = ) alc. ( KOH C = NaNH ₂ D = ) Red hot Fe tube
Step-by-step solution
The reaction sequence is as follows: Step [A]: Ethylene ( C₂H₄ ) reacts with Br₂/CCl₄ to form 1,2-dibromoethane ( CH₂Br-CH₂Br ). Step [B]: 1,2-dibromoethane undergoes dehydrohalogenation using alcoholic KOH to form vinyl bromide ( CH₂=CH-Br ). Step [C]: Vinyl bromide is treated with NaNH₂ (a strong base) to undergo further dehydrohalogenation to form acetylene ( C₂H₂ ). Step [D]: Acetylene undergoes cyclic polymerization when passed through a red hot iron (Fe) tube to form benzene ( C₆H₆ ). Comparing these steps wi