Ethyl bromide reacts with lead-sodium alloy to form

How many of the four monochloro derivatives of $(CH_3)_2CHCH_2CH_3$ are optically active?

In the following sequence of reactions, the major products $B$ and $C$ respectively are:

Most reactive for $S_{N}1$ reaction is

Identify $A, B, C, D, E, R$ and $R^1$ in the following reactions:
$Cyclohexyl-Br + Mg$ $\xrightarrow{dry\,ether} A$ $\xrightarrow{H_2O} B$
$R-Br + Mg$ $\xrightarrow{dry\,ether} C$ $\xrightarrow{D_2O} CH_3-CH(D)-CH_3$
$CH_3-C(CH_3)_2-C(CH_3)_2-CH_3 \xleftarrow{Na/ether} R^1-X$ $\xrightarrow{Mg} D$ $\xrightarrow{H_2O} E$

$1,4$-dichlorohexane $(1 \ mole)$ + $NaI$ $(1 \ mole)$ $\xrightarrow{Acetone}$ Product of the reaction is