Which one of the following statements is incorrect regarding polyhalogen compounds?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Triiodomethane can be used as an anaesthetic agent.
Carbon compounds with more than one halogen atom (polyhalogen compounds) have many industrial and medical uses.
Option (1) Dichloromethane can be used as a propellant in aerosols. — A correct use. It is widely used as a solvent, a paint remover and an aerosol propellant.
Option (2) Trichloromethane can be used for the production of freon refrigerant R-22. — A correct use. This is the major present-day use of chloroform; it was once an anaesthetic but has been replaced by safer ones.
Option (3) Triiodomethane can be used as an anaesthetic agent. — The incorrect statement. Iodoform was used earlier as an antiseptic (owing to the free iodine it releases), not as an anaesthetic; the statement confuses it with chloroform.
Option (4) Tetrachloromethane can be used in the manufacture of refrigerants and propellants for aerosol cans. — A correct use. \( \ce{CCl4} \) is produced in large quantities for this purpose.
NCERT (2026-27 edition):
Dichloromethane (Methylene chloride) – “Dichloromethane is widely used as a solvent as a paint remover, as a propellant in aerosols, and as a process solvent in the manufacture of drugs. …”
Trichloromethane (Chloroform) – “… The major use of chloroform today is in the production of the freon refrigerant R-22. It was once used as a general anaesthetic in surgery but has been replaced by less toxic, safer anaesthetics, such as ether. …”
Tetrachloromethane (Carbon tetrachloride) – “It is produced in large quantities for use in the manufacture of refrigerants and propellants for aerosol cans. …”