Which reagent is commonly used to convert an alcohol to an alkyl chloride?

• A. PCC
• B. H2SO4
• C. PCl5
• D. SOCl2

Answer: (D)

Transforming an alcohol into an alkyl chloride relies on making the OH a much better leaving group and supplying a chloride to take its place in one step. Thionyl chloride achieves this efficiently: the alcohol reacts to form a chlorosulfite intermediate, which then collapses to give the alkyl chloride while releasing sulfur dioxide and hydrogen chloride as byproducts. Those gases exit the reaction, helping push the reaction to completion and making workup easier. This method works well for primary and secondary alcohols and is widely favored in practice.

PCC would oxidize alcohols to carbonyl compounds, not chlorides. H2SO4 mainly causes dehydration to alkenes, not chlorination. PCl5 can convert alcohols to chlorides too, but it’s harsher and less convenient in many cases. So, thionyl chloride is the standard choice for this transformation.