Elimination of bromine from $2-$bromobutane results in the formation of

Which of the following compounds will not undergo Friedel-Crafts reaction with benzene?

For the reaction:
$RCH_2Br + I^{-} \stackrel{\text{Acetone}}{\longrightarrow} RCH_2I + Br^{-}$
The correct statement is:

Which of the following is an example of an $S_N2$ reaction?

Arrange the compounds of each set in order of reactivity towards $S_{N}2$ displacement:
$(i)$ $2-Bromo-2-methylbutane$,$1-Bromopentane$,$2-Bromopentane$
$(ii)$ $1-Bromo-3-methylbutane$,$2-Bromo-2-methylbutane$,$2-Bromo-3-methylbutane$
$(iii)$ $1-Bromobutane$,$1-Bromo-2,2-dimethylpropane$,$1-Bromo-2-methylbutane$,$1-Bromo-3-methylbutane$.

The product $X$ is
[Image: $1-$chloro$-1-$($2$-chloroethyl)cyclopentane] $\xrightarrow{LiBr/DMSO, S_N2 \text{ conditions}}$ Major product $(X)$