Interactive learning platform to visualize and understand organic chemistry reaction pathways
Reaction Library
Quick Tip
Mechanisms show how electrons move during reactions. Follow the electron flow to understand bond changes!
Welcome to Reaction Mechanisms!
Organic reaction mechanisms are step-by-step descriptions of how reactions occur at the molecular level. Understanding these pathways is key to mastering organic chemistry.
Select a reaction from the left panel to explore its mechanism in detail with interactive animations and explanations.
Nucleophilic Substitution (SN²) Mechanism
Bimolecular
SN² reactions involve a nucleophile attacking the electrophilic carbon from the opposite side of the leaving group. All bonds change in one concerted step.
Key Features:
Concerted mechanism (single step)
Stereospecific (inversion of configuration)
Rate depends on both substrate and nucleophile
Preferred for primary and methyl substrates
Mechanism Steps:
The nucleophile (OH⁻) approaches the carbon atom from the opposite side of the leaving group (Br⁻)
Simultaneous bond formation (C-OH) and bond breaking (C-Br)
The transition state forms with partial bonds to both groups
Complete inversion of configuration at the carbon center
Nucleophilic Substitution (SN¹) Mechanism
Unimolecular
SN¹ reactions occur in two steps: first the leaving group departs to form a carbocation intermediate, then the nucleophile attacks.
Key Features:
Two-step mechanism
Forms carbocation intermediate
Racemization occurs at chiral centers
Rate depends only on substrate concentration
Preferred for tertiary and secondary substrates
Often competes with E1 elimination
Step 1: Ionization
Step 2: Nucleophilic Attack
Energy Profile:
The energy diagram shows the two-step process with a carbocation intermediate. The first step (formation of carbocation) is the rate-determining step.
Elimination (E2) Mechanism
Bimolecular
E2 reactions involve concerted removal of a proton and a leaving group to form a double bond. The base abstracts a proton while the leaving group departs.
Key Features:
Concerted mechanism (single step)
Requires strong base and good leaving group
Anti-periplanar geometry required
Rate depends on both substrate and base
Often competes with SN2 reactions
Stereochemistry:
For cyclohexane systems, the hydrogens and leaving groups must be in the anti position (dihedral angle of 180°). This requirement often determines which product will form when multiple β-hydrogens are available.
