Question

What factors affect $S{{N}_{2}}$ reactions?

Answer 1

The nucleophilic substitution reaction of the leaving group (which usually comprises of halide groups or other electron-withdrawing groups) with a nucleophile in a particular organic molecule is the $S{{N}_{2}}$ reaction mechanism.
The interaction between the two species, namely the nucleophile and the organic molecule, determines the rate of this reaction.

Complete answer:
The $S{{N}_{2}}$ reaction is a synchronous nucleophilic substitution process in which a bond is broken and a new one is created. The rate-determining phase of the reaction involves two reacting species. Substitution Nucleophilic Bimolecular is the abbreviation for Substitution Nucleophilic Bimolecular. Bimolecular nucleophilic substitution, associative substitution, and exchange mechanism are all terms used to describe this sort of reaction.
Factors affecting rate of reaction
The rear of the substrate is free of obstructions, making the creation of a carbon-nucleophile connection simple. As a result, methyl and primary substrates are easily nucleophilic substituted.
The rate of the reaction is accelerated by strong anionic nucleophiles. With a higher negative charge, nucleophilicity rises, and a strong nucleophile may readily establish the carbon-nucleophile bond.
The nucleophile is unaffected by polar aprotic solvents, while polar solvents form hydrogen bonds with the nucleophile. Acetone is an excellent solvent for this reaction.
The poor bond strength of the leaving group's connection with carbon, as well as the stability of the anion of the leaving group, aid in increasing the pace of $S{{N}_{2}}$ reactions.
A good nucleophile has an unstable negative charge but isn't too basic to extract hydrogen rather than attack the electrophile. It should also be more compact in order to approach and interact with the electrophile.
An electrophile with a net polar positive moment or charge that is not sterically inhibited is a good electrophile. $S{{N}_{2}}$ is nearly difficult for tertiary electrophiles.

Note:
When it comes to solvents, we want something nonpolar and aprotic. We don't want any of the solvent molecules to reduce the nucleophilicity or electrophilicity of the reactants, therefore they're nonpolar. Because we want our nucleophile to target the electrophilic reactant rather than a hydrogen, we employ aprotic.