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प्रश्न
Write the mechanism of acid-catalysed dehydration of ethanol to yield ethene.
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उत्तर
In the presence of conc. acids such as H3PO4 and H2SO4 alcohols undergo dehydration to yield alkenes.
\[\ce{\underset{Ethanol}{H3C - CH2 - OH} ->[conc{.} H+/\Delta] \underset{Ethene}{CH2 = CH2} + H2O}\]
The mechanism for this reaction is:
Step 1: Protonation of ethanol:
Step 1: Formation of carbocation:
Step 3: Formation of ethene and regeneration of proton:
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\[\begin{array}{cc}
\phantom{...................................}\ce{Br}\\
\phantom{..................................}|\\
\ce{CH3 - CH - CH - CH3 ->[HBr] CH3 - C - CH2 - CH3}\\
|\phantom{.........}|\phantom{...................................}|\phantom{...........}\\
\ce{CH3}\phantom{...}\ce{OH}\phantom{...............................}\ce{CH3}\phantom{.......}\\
\end{array}\]
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Write the mechanism of acid-catalysed dehydration of ethanol to yield ethene.
Write the mechanism of acid dehydration of ethanol to yield ethene.
