2-Methylbutan-2-ol is treated separately with (i) conc. HBr at room temperature and (ii) conc. H2SO4 at 440 K. The main products are, respectively,

2-bromo-2-methylbutane; 2-methylbut-2-ene

2-methylbut-2-ene; 2-bromo-2-methylbutane

1-bromo-2-methylbutane; 2-methylbut-1-ene

2-bromo-2-methylbutane; 2-methylbut-2-ene

2-bromo-2-methylbutane; 2-methylbutan-2-yl ether

JEE Advanced levelSingle correct optionDifficulty 3 of 3o4162

2-Methylbutan-2-ol is treated separately with (i) conc. $HBr$ at room temperature and (ii) conc. $H X_{2} SO X_{4}$ at 440 K. The main products are, respectively,

The tertiary cation from the protonated alcohol is captured by the good nucleophile

Br X^{-}

at low temperature (SN1). With non-nucleophilic hydrogen sulfate at high temperature, loss of a proton wins (E1, Saytzeff), giving 2-methylbut-2-ene.