E2 Elimination

This animation of an E2 elimination of a tertiary alkyl bromide demonstrates how orbital alignment controls reactivity in elimination reactions. Newman projections and molecular orbital depictions are used to illustrate the key geometric requirements.

1. A Newman projection shows the critical antiperiplanar arrangement of the C-H and C-Br bonds. The C-H σ bonding orbital and C-Br σ* antibonding orbital overlap optimally in this geometry, which facilitates electron flow during elimination.
2. The hydroxide ion abstracts the proton, with electrons from the C-H σ bond beginning to flow into the C-Br σ* orbital. As the bromide leaves, the electrons from the C-H σ bond visibly redistribute to form the new π bond.

This orbital-driven process explains why E2 eliminations require antiperiplanar geometry and occur in a concerted fashion.