The most preferred method for the preparation of pure alkyl chlorides from alcohols is:
1. \(\mathrm{R}-\mathrm{OH}+\mathrm{HCl} \xrightarrow{\mathrm{ZnCl}_2} \mathrm{R}-\mathrm{Cl}+\mathrm{H}_2 \mathrm{O}\)
2. \(\mathrm{R}-\mathrm{OH}+\mathrm{PCl}_5 \rightarrow \mathrm{R}-\mathrm{Cl}+\mathrm{POCl}_3+\mathrm{HCl}\)
3. \(\mathrm{R}-\mathrm{OH}+\mathrm{SOCl}_2 \rightarrow \mathrm{R}-\mathrm{Cl}+\mathrm{SO}_2+\mathrm{HCl}\)
4. \(\mathrm{R}-\mathrm{OH}+\mathrm{PCl}_3 \rightarrow \mathrm{R}-\mathrm{Cl}+\mathrm{H}_3 \mathrm{PO}_3\)