The formation of alkene from alkyl halide is an example of

The following reaction is supposed to take place through the $S_N1$ mechanism: $CH_3-C(Ph)(OH)-CH_2-CH_3 \xrightarrow{HI} \text{products}$. If the configuration of the substrate is $D$,then the configuration of the products will be:

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A):$ $R-I$ undergoes $S_N2$ reaction faster than $R-Cl$.
Reason $(R):$ Iodine is a better leaving group because of its large size.
In the light of the above statements,choose the correct answer from the options given below:

Which of the following,when undergoing addition of $HBr$,will form $ONLY$ a pair of diastereomers?

The correct order of the rate of reaction of the following reactants with a nucleophile by $S_{N}1$ mechanism is:
(Given: Structure $I$ and $II$ are rigid)

Which type of rate is observed in dehydrohalogenation ($\beta$-elimination) reaction of alkyl halide?