Give the structure of $\mathrm{X}$.

In the following reaction the most probable product will be:

In which of the following reaction ${\mathrm{CH}}_4$, will be obtained.

$\left(\mathrm{i}\right) {\mathrm{CH}}_3-\mathrm{MgBr}+{\mathrm{CH}}_3-\mathrm{C}\equiv \mathrm{CH}$

$\left(\mathrm{ii}\right)$ 

$\left(\mathrm{iii}\right)\mathrm{ }{\mathrm{CH}}_3-\mathrm{MgBr}+\mathrm{HCN}$

$\left(\mathrm{iv}\right)$ 

Identify the major product.

In ${\mathrm{S}}_{\mathrm{N}}2$ substitution reaction :-

$\mathrm{R}-\mathrm{Br}+\mathrm{Nal}\stackrel{\mathrm{Acetone}}{\to }\mathrm{R}-\mathrm{l}+\mathrm{NaBr}$

Which one of the following has the highest relative rate?

Consider the following alcohols:

The order of decreasing reactivities of these alcohols towards nucleophilic substitution with $\mathrm{HBr}$ is: