The compound that will undergo $S_N 1$ reaction with the fastest rate is

Which of the following represents the $(R)$-enantiomer of $1$-chloro-$1$-deutero-$1$-($4$-chlorophenyl)methane?

Consider the following reaction sequence:
$Cyclohexylidene-methane$ $\xrightarrow[CH_3OH]{Br_2} A$ $\xrightarrow{KCN} B$
Identify the correct structures for $A$ and $B$ from the given options:
$A$ is:
$A) \text{ 1-(bromomethyl)-1-methoxycyclohexane}$
$B) \text{ 1-(methoxymethyl)-1-bromocyclohexane}$
$B$ is:
$C) \text{ 1-(bromomethyl)-1-methoxycyclohexane}$
$D) \text{ 1-(cyanomethyl)-1-methoxycyclohexane}$

Identify the product formed when $2-$Bromobutane is heated with aqueous solution of sodium hydroxide.

Which of the following is least reactive towards $SN^{1}$ reactions?

Vinylcyclopentane $\xrightarrow{HCl}$ Major product is