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Preparation of ethers by acid dehydratio...

Preparation of ethers by acid dehydration of secondary or tetiary alcohols is not a suitable method. Give reason.

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Acid-catalysed dehydratrion of `1^(@)` alcohols to ethers occurs by `SN^(2)` reaction involving nucleophilic attack by the alcohol molecule on the protonated alcohol molecule.

Under these conditions, `2^(@)` and `3^(@)` alcohols, however, give alkenes rathenes than ethers. The reason being that due, to steric hindrance, nucleophilic attack by the alcohol molecule on the protonatedc alcohol molecule does not occur. Insted protonated `2^(@)` and `3^(@)` alcohols lose a molecule of water form stable `2^(@)` and `3^(@)` carbocations. These carbonations prefer to lose a proton to form alkenes rather than undergoing nucleophilic attack by alcohol molecules to form ethers.


Similarly, `3^(@)` alcohols give alkenes rather than ethers.

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Preparation of ethers by acid dehydration of secondary or tertiary alcohols is not a suitable method. Give reason.

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Knowledge Check

  • Preparation of diethyl ether by dehydration of alcohol is an:

    A
    `SN^(1)` reaction
    B
    `SN^(2)` reaction
    C
    Nucleophilic addition reaction
    D
    Elimination reaction

  • Dehydration of tertiary alcohols with Cu at 573 gives

    A
    Aldehydes
    B
    Ketones
    C
    Alkenes
    D
    None of these

  • Acidic dehydration of the following alcohols is in the order :

    A
    `(I)lt(II)lt(III)lt(IV)`
    B
    `(I)gt(II)gt(III)gt(IV)`
    C
    `(III)lt(II)lt(I)lt(IV)`
    D
    `(II)lt(III)lt(IV)lt(I).`

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