Question

Which of the following agents can be used for dehydration of alcohols to yield alkenes?

• A. $\mathrm{Conc}.H_2{\mathrm{SO}}_4$
• B. $\mathrm{Conc}.H_3{\mathrm{PO}}_4$
• C. $\mathrm{Hydrated}{\mathrm{ZnCl}}_2$
• D. $\mathrm{Anhydrous}{\mathrm{ZnCl}}_2$

Answer 1

Answer: (A), (B), (D)

The correct options are
A $\mathrm{Conc}.H_2{\mathrm{SO}}_4$
B $\mathrm{Conc}.H_3{\mathrm{PO}}_4$
D $\mathrm{Anhydrous}{\mathrm{ZnCl}}_2$

Dehydration of alcohols results in the formation of alkenes. $\mathrm{Conc}.H_2{\mathrm{SO}}_4,\mathrm{conc}.H_3{\mathrm{PO}}_4$ and $\mathrm{anhydrous}{\mathrm{ZnCl}}_2$ are some of the strongest dehydrating agents. All of these can be used for dehydration of alcohols under specific conditions. e.g. for conversion of a tertiary alcohol into alkene, $20\%\mathrm{conc}.H_3{\mathrm{PO}}_4$ can be used at 360K.