Which of the following is a characteristic of $S_N2$ reaction?

(A). Concentration of both reactants determines the reaction rate.
(B). Proceeds with inversion of configuration.
(C). The transition state involves central carbon bonded to five species.
(D). Occurs in polar protic solvent

Choose the correct answer from the options given below:

(A), (B) and (C) only

The correct answer is Option (2) → (A), (B) and (C) only

The SN₂ (Substitution Nucleophilic Bimolecular) reaction occurs through a single-step mechanism where the nucleophile attacks the substrate simultaneously as the leaving group departs

(A) Concentration of both reactants determines the reaction rate

The rate law for an SN₂ reaction is:

Rate = k [RX][Nu⁻]

Thus, the rate depends on the concentration of both the alkyl halide (substrate) and the nucleophile.

Therefore, this statement is correct.

(B) Proceeds with inversion of configuration

In SN₂ reactions, the nucleophile attacks from the back side of the carbon atom, leading to Walden inversion of configuration. Thus, this statement is correct.

(C) Transition state involves central carbon bonded to five species

During the reaction, the carbon forms a pentacoordinate transition state, where it is partially bonded to:

• Three substituents

• Incoming nucleophile

• Leaving group

Thus, the transition state involves five species.

Therefore, this statement is correct.

(D) Occurs in polar protic solvent

SN₂ reactions are favored in polar aprotic solvents such as acetone, DMSO, or DMF because these solvents do not strongly solvate the nucleophile. Polar protic solvents generally favor SN₁ reactions.

Thus, this statement is incorrect.