Home
Class 12
CHEMISTRY
when 3-methylbutan-2-ol is treated with ...

when 3-methylbutan-2-ol is treated with HBr, the following reaction takes place:

Give the mechanism of this reaction.
Hint : The secondary carbocation formed in step II rearranges to a more stable tetriary carbocation by a hydride ion shift form the third carbon atom.

Text Solution

Verified by Experts

The protonation of given alcohol followed by loss of water gives a `2^(@)` carbocation (I), which being unstable rearranges by 1,2-hydride shift to form a more stable `3^(@)` carbocation (II). Nuclueophilic attack by `Br^(-)` ion on this carbocation (II) gives the final product.
Doubtnut Promotions Banner Mobile Dark
|

Topper's Solved these Questions

  • ALCOHOL,PHENOL AND ETHERS

    CENGAGE CHEMISTRY|Exercise Exercises Linked Comprehension|60 Videos

  • ALCOHOL,PHENOL AND ETHERS

    CENGAGE CHEMISTRY|Exercise Exercises Multiple Correct|35 Videos

  • ALCOHOL,PHENOL AND ETHERS

    CENGAGE CHEMISTRY|Exercise Exercises Subjective|25 Videos

  • ALIPHATIC AND AROMATIC ALDEHYDES AND KETONES

    CENGAGE CHEMISTRY|Exercise Archives Subjective|29 Videos

Similar Questions

Explore conceptually related problems

When 3-methylbutan-2-ol is treated with HBr, the following reaction takes place: CH_(3)-underset(CH_(3))underset("| ")("C ")H-underset(OH)underset("| ")("C")H-CH_(3)overset(HBr)rarr CH_(3)-overset(Br)overset("| ")underset(CH_(3))underset("| ")("C ")-CH_(2)-CH_(3) Give a mechanism for this reaction. (Hint : The secondary carbocation formed in step II rearranges to a more stable tertiary carbocation by a hydride ion shift from 3rd carbon atom.

When 3, 3-dimethylbutan-2-ol is treated with concentrated HI, a rearrangement occurs. Name the alkyl iodide formed showing the steps of the reaction.

Knowledge Check

  • Which one of the following carbonyl compound when treated with dilute acid forms the more stable carbocation ?

    A
    `CH_(3)- overset(O) overset(||)C - CH_(3)`
    B
    C
    D
    `C_(6)H_(5)- overset(O)overset(||)C - C_(6)H_(5)`

  • Di-tert-glycols rearrange in the presence of acid to give alpha -trtiary ketones. The trivial name of the simplest glycol of this type is pinacol, and this type of reaction therefore is named pinacol rearrangement (in this specific case, the reaction is called a pinacol-pinacolone rearrangement). The rearrangement involves 4 steps. one of the hydroxyl group is protonated in the first step. A molecule of water is eliminated in the second step and a tertiary carbocation is formed. the carbocation rearranges in the third step into a more stable carboxonium ion via a [1, 2] rearrangement. In the last step, the carboxonium ion is deprotonated and the product ketone is obtained. How many products obtained in above reaction ?

    A
    1
    B
    2
    C
    3
    D
    4

  • Di-tert-glycols rearrange in the presence of acid to give alpha -trtiary ketones. The trivial name of the simplest glycol of this type is pinacol, and this type of reaction therefore is named pinacol rearrangement (in this specific case, the reaction is called a pinacol-pinacolone rearrangement). The rearrangement involves 4 steps. one of the hydroxyl group is protonated in the first step. A molecule of water is eliminated in the second step and a tertiary carbocation is formed. the carbocation rearranges in the third step into a more stable carboxonium ion via a [1, 2] rearrangement. In the last step, the carboxonium ion is deprotonated and the product ketone is obtained. What is R.D.S. of pinacol-pinacolone rearrangement ?

    A
    I step
    B
    II step
    C
    III step
    D
    IV step

    • Similar Questions

    Explore conceptually related problems

    If 3-chloromethylhexane is treated with C_(2)H_(5)Ona//C_(2)H_(5)OH, E_(2) elimination reaction takes place predominantly. How many different alkenes would be formed ?

    Di-tert-glycols rearrange in the presence of acid to give alpha -trtiary ketones. The trivial name of the simplest glycol of this type is pinacol, and this type of reaction therefore is named pinacol rearrangement (in this specific case, the reaction is called a pinacol-pinacolone rearrangement). The rearrangement involves 4 steps. one of the hydroxyl group is protonated in the first step. A molecule of water is eliminated in the second step and a tertiary carbocation is formed. the carbocation rearranges in the third step into a more stable carboxonium ion via a [1, 2] rearrangement. In the last step, the carboxonium ion is deprotonated and the product ketone is obtained. Product 'P' is :

    Di-tert-glycols rearrange in the presence of acid to give alpha -trtiary ketones. The trivial name of the simplest glycol of this type is pinacol, and this type of reaction therefore is named pinacol rearrangement (in this specific case, the reaction is called a pinacol-pinacolone rearrangement). The rearrangement involves 4 steps. one of the hydroxyl group is protonated in the first step. A molecule of water is eliminated in the second step and a tertiary carbocation is formed. the carbocation rearranges in the third step into a more stable carboxonium ion via a [1, 2] rearrangement. In the last step, the carboxonium ion is deprotonated and the product ketone is obtained. Product (A) is :

    A : When 3,3-dimethyl butan - 2 - ol is heated in presence of concentrated H_(2)SO_(4) then 2, 3-dimethyl but -2-ene is formed as major product . R : In this reaction , carbocation is formed as an intermediate

    Under common reaction conditions, a carboncation rearranges to another carbocation of equal or greater stability. For example secondary carbocation will rearrange to a tertiary carbocation. It will not rearrange to a less stable primary carbocation. This generalization is not absolute, and because there is not is a high energy barrier to the rearrangement of carbocations, rearrangement to a less stable cation can occur if it offers the chance to forme a more stable product. In which of the following cations rearrangement takes place?

    Home
    Profile