Which of the following expressions is representative of the rate law for a $S_{N}2$ reaction?

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 $Y$

If all the nucleophilic substitution reactions at saturated carbon atoms in the above sequence of reactions follow $S_N2$ mechanism, then $\underline{E}$ and $\underline{E}$ will be respectively,

The following reaction is supposed to take place through the $S_N1$ mechanism: $CH_3-C(Ph)(OH)-CH_2-CH_3 \xrightarrow{HI} \text{products}$. If the configuration of the substrate is $D$,then the configuration of the products will be:

Which of the following compounds will not undergo Friedel-Crafts reaction with benzene?

For the compounds $CH_3Cl$,$CH_3Br$,$CH_3I$,and $CH_3F$,the correct order of increasing $C$-halogen bond length is