The strongest nucleophile in a polar protic solvent is:

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

The major product of the following reaction is:

The decreasing order of reactivity of the following compounds towards nucleophilic substitution $(S_{N}2)$ is :

Which of the following reactions is used for the conversion of alkyl chloride to alkyl iodide?

$A$ dihaloalkane '$X$',having formula $C_{3}H_{6}Cl_{2}$,on hydrolysis gives a compound that can reduce Tollen's reagent. The compound '$X$' is