JEE Main 2024 — Haloalkanes and Haloarenes Question with Solution

Statement - I: Rate of ${\mathrm{S}}_{\mathrm{N}}2\propto [\mathrm{R}-\mathrm{X}]\left[{\mathrm{Nu}}^{-}\right]$
${\mathrm{S}}_{\mathrm{N}}2$ reaction is favoured by high concentration of nucleophile $\left({\mathrm{Nu}}^{-}\right)\&$ less crowding in the substrate molecule.

${\mathrm{S}}_{\mathrm{N}}2$ Reaction Mechanism

This reaction proceeds through a backside attack by the nucleophile on the substrate. The nucleophile approaches the given substrate at an angle of ${180}^{°}$ to the carbon-leaving group bond. The carbon-nucleophile bond forms and carbon-leaving group bond breaks simultaneously through a transition state.

Now, the leaving group is pushed out of the transition state on the opposite side of the carbon-nucleophile bond, forming the required product. It is important to note that the product is formed with an inversion of the tetrahedral geometry at the atom in the centre.

Statement - II: Solvolysis follows ${\mathrm{S}}_{\mathrm{N}}1$ path.

he ${\mathrm{S}}_{\mathrm{N}}1$ reaction is a nucleophilic substitution reaction where the rate-determining step is unimolecular. It is a type of organic substitution reaction. ${\mathrm{S}}_{\mathrm{N}}1$ stands for substitution nucleophilic unimolecular. Thus, the rate equation (which states that the ${\mathrm{S}}_{\mathrm{N}}1$ reaction is dependent on the electrophile but not on the nucleophile) holds in situations where the amount of the nucleophile is far greater than the amount of the carbocation intermediate.

This reaction involves the formation of a carbocation intermediate. It is generally seen in the reactions of tertiary or secondary alkyl halides with secondary or tertiary alcohols under strongly acidic or strongly basic conditions. The ${\mathrm{S}}_{\mathrm{N}}1$ reaction is often referred to as the dissociative mechanism in inorganic chemistry.

Both are correct statements.