Bondline / Reactions

SN2 substitution

A nucleophile replaces a leaving group in one concerted step. Best for methyl and primary substrates; the carbon inverts like an umbrella.

Substitution · 1 step

Conditions

Good nucleophile, polar aprotic solvent (e.g. acetone, DMSO). Rate = k[RX][Nu⁻].

Mechanism

Red curly arrows show where each pair of electrons moves.

HO−BrHOBr−++
MechanismHydroxide attacks carbon from the side opposite bromine while the C–Br bond breaks, all in one step.

About substitution reactions

In a substitution, a nucleophile replaces a leaving group on a saturated carbon. Whether it happens in one step (SN2) or through a carbocation (SN1) depends on the substrate, the nucleophile and the solvent.

Practise this mechanismDraw the curly arrows yourself and Bondline checks each one. Or add it to your notes and watch it in 3D.

Open in Bondline