3,3-Dimethylbutan-2-ol, CH3-CH(OH)-C(CH3)3, is heated with concentrated HBr. The main bromide obtained is

JEE Advanced levelSingle correct optionDifficulty 3 of 3o3040

3,3-Dimethylbutan-2-ol, $CH X_{3} - CH (OH) - C (CH X_{3}) X_{3}$ , is heated with concentrated $HBr$ . The main bromide obtained is

Protonation turns OH into the leaving group

H X_{2} O

and ionisation gives the secondary cation

CH X_{3} - CH X^{+} - C (CH X_{3}) X_{3}

. A 1,2-methyl shift gives the tertiary cation

(CH X_{3}) X_{2} C X^{+} - CH (CH X_{3}) X_{2}

, which bromide captures to give

(CH X_{3}) X_{2} CBr - CH (CH X_{3}) X_{2}

, 2-bromo-2,3-dimethylbutane. (Unrearranged 2-bromo-3,3-dimethylbutane is only a minor product.)