Under the specified conditions,substrate $X$ undergoes substitution and elimination reactions to give products $A - D$. $A$ and $B$ are stereoisomers,but not enantiomers. $C$ and $D$ are enantiomers. $A$ is not an isomer of $C$. Which of the following could be the starting material $X$ ?
$X \xrightarrow[\Delta]{H_2O} A + B + C + D$

In the following reaction sequence,the correct structure$(s)$ of $X$ is (are)
$X$ $\xrightarrow[2) NaI, Me_2CO]{1) PBr_3, Et_2O}$ $\xrightarrow{3) NaN_3, HCONMe_2} \text{enantiomerically pure product}$

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 $Y$?

The rate-limiting step of an $S_N1$ reaction follows the sequence shown below. Based on the assumption that $R$ contains $3$ different groups,which statement is true?
$\mathop R\limits^{\delta \oplus } \,\mathop {Br}\limits^{\delta \Theta } \, \rightleftharpoons \,\mathop {\boxed{{R^ \oplus }Br^\Theta }}\limits_{(a)} \,\,\, \rightleftharpoons \,\mathop {\boxed{{R^ \oplus }}\,\boxed{Br^\Theta }\,}\limits_{(b)} \,\, \rightleftharpoons $ ${\boxed{{R^ \oplus }}}$ $ + $ $\mathop {\,\boxed{Br^\Theta }\,}\limits_{(c)} \,$

Two isomers $(A)$ and $(B)$ with molar mass $184 \ g/mol$ and elemental composition $C, 52.2 \ \%; H, 4.9 \ \%$ and $Br, 42.9 \ \%$ give benzoic acid and $p$-bromobenzoic acid,respectively,on oxidation with $KMnO_4$. Isomer '$A$' is optically active and gives a pale yellow precipitate when warmed with alcoholic $AgNO_3$. Isomer '$A$' and '$B$' are,respectively .... .

The correct order for increasing reactivity towards $S_N1$ substitution for the following compounds is:
$1. CH_3CH_2Br$
$2. CH_2=CHCH(Br)CH_3$
$3. CH_2=CHBr$
$4. CH_3CH(Br)CH_3$