Consider all the structural isomers with molecular formula C_5 H_11 Br are separately treated with KOH ( aq ) to give respective substitution…

Consider all the structural isomers with molecular formula $\displaystyle \mathrm{C}_5 \mathrm{H}_{11} \mathrm{Br}$ are separately treated with $\displaystyle \mathrm{KOH}(\mathrm{aq})$ to give respective substitution products, without any rearrangement. The number of products which can exhibit optical isomerism from these is $\displaystyle \_\_\_\_$.