Write the mechanism of acid dehydration of ...

NCERT Class XII Chemistry
Chapter - Alcohols, Phenols and Ethers
Questions with Solutions

Question : 19 of 45

Marks: +1, -0

Write the mechanism of acid dehydration of ethanol to yield ethene.

Solution:

In the presence of conc. acids such as

\mathrm{H_3PO_4}

and

\mathrm{H_2SO_4}

, alcohols undergo dehydration to yield alkenes.

\underset{\text{Ethanol}}{\mathrm{H_3C-CH_2-OH}} \xrightarrow{\mathrm{conc.H}^{+}/\Delta} \underset{\text{Ethane}}{\mathrm{CH_2=CH_2}} + \mathrm{H_2O}

The mechanism for this reaction is :

Step 1 : Protonation of ethanol

Step 2 : Formation of carbocation

Step 3 : Formation of ethene and regeneration of proton

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