$A$ bromoalkane $X$ reacts with magnesium in dry ether to form compound $Y$. The reaction of $Y$ with methanal followed by hydrolysis yields an alcohol having molecular formula $C_{4}H_{10}O$. The compound $X$ is

The order of reactivity of the following alkyl halides for a $S_N2$ reaction is

Given below are two statements:
Statement $I$: $(Et)_2N-CH_2CH_2Cl$ will undergo alkaline hydrolysis at a faster rate than $(Et)_2CH-CH_2CH_2Cl$.
Statement $II$: Intramolecular substitution takes place first by involving the lone pair of electrons on nitrogen.
In the light of the above statements,choose the most appropriate answer from the options given below:

Select the reagent that will yield the greater amount of substitution on reaction with $CH_3CH_2Br$.

Which of the following can be used as the halide component for Friedel-Crafts reaction?

Predict the order of reactivity of the following compounds in $S_{N}1$ and $S_{N}2$ reactions:
$(i)$ The four isomeric bromobutanes
$(ii)$ $C_{6}H_{5}CH_{2}Br$,$C_{6}H_{5}CH(C_{6}H_{5})Br$,$C_{6}H_{5}CH(CH_{3})Br$,$C_{6}H_{5}C(CH_{3})(C_{6}H_{5})Br$