Predict the order of reactivity of the following four isomers towards $S_{N}2$ reaction.
$(I)$ $CH_{3}CH_{2}CH_{2}CH_{2}Cl$
$(II)$ $CH_{3}CH_{2}CH(Cl)CH_{3}$
$(III)$ $(CH_{3})_{2}CHCH_{2}Cl$
$(IV)$ $(CH_{3})_{3}CCl$

Which of the following reactions is an example of a nucleophilic substitution reaction?

Among the following chlorides, the compounds which will be hydrolysed most easily and most slowly in aqueous $NaOH$ solution are respectively:
$1$. Methoxymethyl chloride $(CH_3OCH_2Cl)$
$2$. Benzyl chloride $(C_6H_5CH_2Cl)$
$3$. Neopentyl chloride $((CH_3)_3CCH_2Cl)$
$4$. Propyl chloride $(CH_3CH_2CH_2Cl)$

Arrange the leaving group ability of the following groups in decreasing order:
$(I)$ $CH_3-C_6H_4-SO_3^-$,$(II)$ $C_6H_5-SO_3^-$,$(III)$ $N_3^-$,$(IV)$ $Br^-$

What is the product formed when $n$-propyl bromide is reacted with ethanolic potassium hydroxide?

$HBr$ reacts with $CH_2=CH-OCH_3$ at room temperature to give