2-Bromo-3-methylbutane is warmed in ethanol alone (no added base). The major substitution product is

A secondary halide in a polar protic, weakly nucleophilic solvent reacts by the $S_N1$/E1 pathway. The secondary carbocation $\mathrm{(CH_3)_2CH-\overset{+}{C}H-CH_3}$ undergoes a 1,2-hydride shift to the more stable tertiary cation $\mathrm{(CH_3)_2\overset{+}{C}-CH_2CH_3}$. Ethanol traps this cation to give 2-ethoxy-2-methylbutane after loss of a proton. The unrearranged ether is only minor, no water is present for the alcohol, and 2-methylbut-2-ene is the elimination (not substitution) product.