Variables
Description
What is this formula?
The SN2 reaction rate law describes a bimolecular nucleophilic substitution where the reaction rate depends simultaneously on the concentrations of both the substrate and the nucleophile.
When to use it
Use this formula for SN2 reactions where bond formation and bond breaking occur in a single concerted step without formation of a carbocation intermediate.
Example
Given:
k = 0.080 L·mol^-1·s^-1
[RX] = 0.20 mol/L
[Nu^-] = 0.10 mol/L
Formula:
Rate = k[RX][Nu^-]
Substitution:
Rate = 0.080 × 0.20 × 0.10
Result:
Rate = 1.6×10^-3 mol·L^-1·s^-1
Applications
Organic reaction kinetics
Nucleophilic substitution
Reaction mechanism analysis
Synthetic organic chemistry
Chemical education
Note
This rate law applies to ideal SN2 reactions where a nucleophile attacks the substrate in a single elementary step. Because both species participate in the rate-determining event, the reaction is second order overall. Real systems may deviate from this behavior due to steric hindrance, solvent effects, ion pairing, competing elimination reactions, or changes in mechanism.