Phosgene is formed slowly from which one of the following on exposure to air and sunlight?

Which describes the best stereochemical aspects of the following reaction?
$Ph-C(CH_3)(CD_3)(OH) + HBr \rightarrow \text{Product}$

$n-$Heptane $\xrightarrow[\Delta ]{Al_2O_3} P$ $\xrightarrow{[1 \ mole]}{NBS} Q$. Product $Q$ will be

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 $ ${\boxed{{R^ \oplus }}}$ $ + $ $\mathop {\,\boxed{Br^\Theta }\,}\limits_{(c)} \,$

What is the number of possible enantiomeric pairs formed during the monochlorination of isopentane?

Identify the correct order of reactivity for the reaction with alcoholic $KOH$ for the following compounds:
$(a)$ $2$-bromo-$2,3$-dimethylbutane
$(b)$ $2$-chlorobutane
$(c)$ $2$-bromobutane
$(d)$ $1$-bromopropane