In the given reaction,what is $A$?
$4-methylcyclohexyl bromide + OH^- \xrightarrow{S_N2} A$

Compare the rate of $E_2$ reaction for the following compounds:
$a$: $(CH_3)_3C-Br$
$b$: $CH_3-CH(Br)-CH_3$
$c$: $CH_3-CH_2-Br$

What is $E$?
Cyclohexanone $\xrightarrow{Br_2 + CH_3COOH} A$ $\xrightarrow{Alc. KOH} B$ (Product with six-membered ring) $\xrightarrow[(2) H_2O]{(1) CH_3MgBr} C$ $\xrightarrow{H^{\oplus} + \Delta} D$ $\xrightarrow{HBr (1 \text{ mole})} E$

$A$ solution of $D(+)-1-$chloro$-1-$phenylethane in toluene racemises slowly in the presence of a small amount of $SbCl_5$,due to the formation of:

Hydrolysis of an alkyl bromide $X$ $(C_5H_{11}Br)$ follows first-order kinetics. Reaction of $X$ with $Mg$ in dry ether followed by treatment with $D_2O$ gives $Y$. What is $Y$?

Which of the following is added to chloroform to slow down its aerial oxidation in the presence of light?