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Chemistry Question on Alcohols, Phenols and Ethers

The compound which gives the most stable carbonium ion on dehydration is

A

CH3CHOHCH3CH _{3} CHOHCH _{3}

B

(CH3)3COH\left( CH _{3}\right)_{3} COH

C

CH2=CH−CH2CH2OHCH _{2}= CH - CH _{2} CH _{2} OH

D

CH3OHCH _{3} OH

Answer

(CH3)3COH\left( CH _{3}\right)_{3} COH

Explanation

Solution

The dehydration of tertiary alcohol proceeds via tertiary carbocation intermediate which is most stable. (CH3)3)C−OHtertiary alcohol→−H2O+H+(CH3)3C+3∘carbocation more stable\underset{\text{tertiary alcohol}}{(CH_3)_3)C-OH} \xrightarrow [-H_2O]{+H^+} \underset{3^{\circ} \text{carbocation more stable}}{(CH_3)_3 \overset{+}{C}} CH3CHOHCH3→−H2O+H+CH3CH+−CH32∘carbocation less stableCH_3CHOHCH_3 \xrightarrow [-H_2O]{+H^+}\underset{2^{\circ}\text{carbocation less stable}}{CH_3\overset{+}{CH} - CH_3} CH2=CH−CH2−CH2OH→−H2O+H+CH2=CH−CH2−CH2+1∘ carbocation (least stable)CH _{2}= CH - CH _{2}- CH _{2} OH \xrightarrow[-H_2O]{+H}^{+} CH _{2}= CH - \underset{1^{\circ}\text{ carbocation (least stable)}}{CH _{2}- CH _{2}^{+}} Decreasing order of stability of carbocation is tertiary >> secondary >> primary >> methyl.