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.

Explanation

(i) Alcohols gets protonated.
`CH_(3)-underset(CH_(3))underset(|)(CH)-underset(OH)underset(|)(CH) CH_(3)overset(-H^(+)) to CH_(3)- underset(CH_(3))underset(|)(CH)-CH-CH_(3)`
(ii) Protonated alcohol loses `H_(2)O` molecules to frm `2^(@)` carbocatio.
`CH_(3)-underset(CH_(3))underset(|)(CH)-underset(OH)underset(+|)(CH) overset(-H^(+)) to CH_(3)-underset(2^(@)"carbocation") underset(CH_(3))underset(|)(CH)-overset(+)(CH)-CH_(3)`
(iii) 1,2hybride shift of 2-carbocation gives more stable `3^(@)` carbocatio.

(iv) Nucleophilic attack by `Br^(-)` ion gives alkyl halide.