Question

What happens when carbon tetrachloride is heated with dry hydrogen fluoride in the presence of antimony pentachloride?

Answer 1

When carbon tetrachloride (CCl₄) is heated with dry hydrogen fluoride (HF) in the presence of antimony pentachloride (SbCl₅), substitutive fluorination occurs.

\[\ce{\underset{tetrachloride}{CCl4} + \underset{hydrogen fluoride}{2HF} ->[SbCl5][]\underset{chlorofluorocarbon}{CCl2F2} + 2HCl}\]

This reaction takes place because antimony pentachloride acts as a Lewis acid catalyst, facilitating the substitution of chlorine atoms in CCl₄ with fluorine from HF. The presence of SbCl₅ helps to generate a more reactive electrophilic fluorinating species or activates the substrate for nucleophilic attack by fluoride.