Which of the following reagents convert an alcohol into an alkyl chloride?
(A) Conc. Hydrogen Chloride
(B) Phosphorus trichloride
(C) Phosphorus pentachloride
(D) Thionyl Chloride
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (B), (C) and (D)
Alcohols can be converted into alkyl chlorides (R–Cl) using several chlorinating reagents. These reagents replace the –OH group of alcohol with a chlorine atom.
Different reagents achieve this transformation through different mechanisms.
(A) Concentrated Hydrogen Chloride
Alcohol reacts with concentrated HCl to form an alkyl chloride.
Reaction:
ROH + HCl → RCl + H₂O
This reaction is often carried out in the presence of ZnCl₂ (Lucas reagent) to increase the reaction rate.
Thus this reagent converts alcohol to alkyl chloride.
(B) Phosphorus trichloride (PCl₃)
Phosphorus trichloride reacts with alcohols to produce alkyl chlorides.
Reaction:
3ROH + PCl₃ → 3RCl + H₃PO₃
Thus this reagent also converts alcohol into alkyl chloride.
(C) Phosphorus pentachloride (PCl₅)
Phosphorus pentachloride converts alcohols into alkyl chlorides.
Reaction:
ROH + PCl₅ → RCl + POCl₃ + HCl
Hence this reagent is also used for preparing alkyl chlorides.
(D) Thionyl chloride (SOCl₂)
Thionyl chloride is one of the most preferred reagents for converting alcohols into alkyl chlorides.
Reaction:
ROH + SOCl₂ → RCl + SO₂ + HCl
The by-products (SO₂ and HCl) escape as gases, making the reaction efficient.