What are reactant $X$ and product $Y$ in the following sequence of reactions?
Reactant $X$ $\xrightarrow{\text{Pyridine, } CH_3C_6H_4SO_2Cl}$ Intermediate $\xrightarrow{NaN_3, \text{Ethanol-water}}$ Product $Y$

Identify the product '$B$' in the following reaction sequence:
$CH_3CH_2CH(OH)CH_3 \xrightarrow{PBr_3} A \xrightarrow{Mg, \text{dry ether}} B$

When $AgNO_3$ comes in contact with skin,it leaves a black stain. This is because of

Identify the correct order of reactivity for the $E_2$ reaction with alcoholic $KOH$ for the following compounds:
$(i)$ $(CH_3)_3C-Cl$
(ii) $(CD_3)_3C-Cl$
(iii) $(CT_3)_3C-Cl$

Which alkyl halide from the following pairs would you expect to react more rapidly by an $S_N2$ mechanism? Explain your answer.
$(i)$ $CH_3CH_2CH_2CH_2Br$ or $CH_3CH_2CH(Br)CH_3$
$(ii)$ $CH_3CH_2CH(Br)CH_3$ or $(CH_3)_3CBr$
$(iii)$ $CH_3CH(CH_3)CH_2CH_2Br$ or $CH_3CH_2CH(CH_3)CH_2Br$

The compound having the longest $C-Cl$ bond is: