Which of the following compounds gives a racemic mixture on nucleophilic substitution?
$(a)$ $CH_3-CH(Br)-C_2H_5$
$(b)$ $CH_3-C(Br)(CH_3)-C_2H_5$
$(c)$ $C_2H_5-CH(C_2H_5)-CH_2Br$

Which one of the following is the Swartz reaction?

For the following compounds,the correct statement$(s)$ with respect to nucleophilic substitution reactions is(are):
$I$: Benzyl bromide $(C_6H_5CH_2Br)$
$II$: Cyclohexylmethyl bromide $(C_6H_{11}CH_2Br)$
$III$: tert-Butyl bromide $((CH_3)_3CBr)$
$IV$: $1-$Phenylethyl bromide $(C_6H_5CH(CH_3)Br)$
$A$. $I$ and $III$ follow $S_{N}1$ mechanism
$B$. $I$ and $II$ follow $S_{N}2$ mechanism
$C$. Compound $IV$ undergoes inversion of configuration
$D$. The order of reactivity for $I$,$III$ and $IV$ is: $IV > I > III$

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

$CH_3CH_2CH_2OH$ $\xrightarrow{PCl_5} A$ $\xrightarrow{\text{alcoholic } KOH} B$. The final product $B$ is ...... .

Which of the following reagents,when heated with ethyl chloride,produces ethylene?