Hydrolysis of an alkyl bromide $X$ $(C_5H_{11}Br)$ follows first-order kinetics. Reaction of $X$ with $Mg$ in dry ether followed by treatment with $D_2O$ gives $Y$. What is $Y$?

Which of the following species is most reactive in $S_{N}2$ reaction?

The reaction of $3$-bromocyclohexene with $HBr$ yields $P_1$ and $P_2$ as major dibromo products. What is the relationship between $P_1$ and $P_2$?

What is the product formed when $1$-bromo-$3$-chlorocyclobutane reacts with $2$ moles of sodium in ether?

Which of the following $S_N2$ reactions is the slowest?

The following bimolecular elimination reaction $(E_2)$ is carried out with different halogen leaving groups. The per cent yield of the two products ($2$-hexene and $1$-hexene) for each leaving group is listed below.

Leaving group	Conj. Acid $pK_a$	$\%$-yield of $2$-hexene	$\%$-yield of $1$-hexene
$X = I$	$-10$	$81\%$	$19\%$
$X = Br$	$-9$	$72\%$	$28\%$
$X = Cl$	$-7$	$67\%$	$33\%$
$X = F$	$3.2$	$30\%$	$70\%$

Which of the following statement$(s)$ is/are true concerning this series of $E_2$ reactions?