Which of following reaction names is suitable for the below reaction? 

CH₃CH₂Br + HS^- → CH₃CH₂SH + Br^-

CONCEPT:

SN2 Reaction Mechanism

• SN2 (Substitution Nucleophilic Bimolecular) reactions involve a single step mechanism where the nucleophile attacks the substrate at the same time as the leaving group departs.
• The reaction follows second-order kinetics, meaning the rate of reaction depends on both the concentration of the nucleophile and the substrate.
• The nucleophile performs a backside attack, leading to an inversion of the configuration if the substrate is chiral (known as Walden inversion).

EXPLANATION:

• In the given reaction:

  CH₃CH₂Br + HS^- → CH₃CH₂SH + Br^-

  • The substrate CH₃CH₂Br undergoes nucleophilic substitution.
  • The nucleophile HS^- attacks the carbon atom bonded to the bromine atom (Br) in a backside attack.
  • Bromine (Br) acts as the leaving group and departs simultaneously with the nucleophile attack.
  • This mechanism is consistent with an SN2 reaction, which occurs in one step without the formation of an intermediate.

The reaction mechanism does not involve the formation of a carbocation (as in SN1), nor does it involve intramolecular substitution (SNi) or aromatic substitution (SNar).

Therefore, the correct answer is SN2 reaction.