SN2 Reaction Kinetics | mysimulator.uk

SN2 Kinetics

Nucleophile conc. 50

Substrate (R–X) conc. 50

Temperature 320 K

Leaving-group ability 0.6

Rate (k[Nu][RX])

–

Conversion

–

Collision success

–

Products formed

–

How it works

In an SN2 (bimolecular nucleophilic substitution) reaction, a nucleophile (Nu⁻) collides with an alkyl halide (R–X) and attacks the electrophilic carbon in a single concerted step, pushing out the leaving group (X⁻) as the new bond forms. Because both species must collide with enough kinetic energy and the right orientation, the reaction is second order overall — first order in each reactant.

Nu⁻ + R–X → R–Nu + X⁻
rate = k·[Nu⁻]·[R–X]
k = A·e^(−Ea / RT)

Nucleophile concentration — more Nu⁻ particles mean more collisions per second, raising the rate linearly.
Substrate concentration — more R–X particles likewise raises collision frequency and rate.
Temperature — higher temperature gives particles more kinetic energy, so a larger fraction of collisions clear the activation-energy barrier (Arrhenius equation).
Leaving-group ability — a better leaving group (e.g. I⁻ over F⁻) lowers the activation-energy barrier on the diagram, so collisions succeed more often at the same temperature.

The energy diagram at the top of the canvas tracks the single transition-state hump characteristic of SN2 — one concerted step, no intermediate — while the particle field below shows the same reaction playing out statistically across many molecules at once.

Nucleophile (Nu⁻) Substrate (R–X) Product (R–Nu) Leaving group (X⁻)