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Alcohols, Phenols, and Ethers — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryAlcohols, Phenols, and Ethers1 Mark
MCQ
Which is the best reagent to convert cyclohexanol into cyclohexene?
  • A
    Conc$.\text{HCl}$
  • B
    Conc$.\text{HBr}$
  • ✓
    Conc. $\mathrm{H}_3 \mathrm{PO}_4$
  • D
    $\mathrm{HCl}+\mathrm{ZnCl}_2$
✓

Answer

Correct option: C.
Conc. $\mathrm{H}_3 \mathrm{PO}_4$
Cyclohexanol is used as substrate and phosphoric acid is present as catalyst which promotes the reaction but is not consumed in it. The hydroxyl group in $\ce{R-OH}$ is a poor leaving group because it leaves as hydroxide ion. An acid is used to protonate the alcohol and form $\text{R}−\text{OH}_2^+​$

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