Question

Which of the following substances cannot be used for replacing the $-OH$ group of alcohols by chlorine atom?

• A. Hydrogen chloride
• B. Phosphorus dichloride
• C. Phosphorus tetrachloride
• D. Chlorine molecule

Answer 1

Answer: (D)

Chlorine molecule

Chlorine molecule will not follow substitution mechanism rather it will go through the free radical mechanism. Hence cant get the required result
Hydrogen chloride, Phosphorus dichloride and Phosphorus tetrachloride will produce chloride ion which can susbtitute $-OH$ group by $C{l}^{-}$

$R-OH\underset{\Delta }{\overset{HCl}{\to }}RCl$
$R-OH\underset{\Delta }{\overset{PC{l}_3}{\to }}RCl$
$R-OH\underset{\Delta }{\overset{PC{l}_5}{\to }}RCl$