Continuing the examination of molecular orbital theory as a predictor of chemical reactivity, this lecture focuses on the close analogy among seemingly disparate organic chemistry reactions: acid-base, SN2 substitution, and E2 elimination. All these reactions involve breaking existing bonds where LUMOs have antibonding nodes while new bonds are being formed. The three-stage oxidation of ammonia by elemental chlorine is analyzed in the same terms. The analysis is extended to the reactivity of the carbonyl group and predicts the trajectory for attack by a high HOMO. This predicted trajectory was validated experimentally by Bürgi and Dunitz, who compared numerous crystal structures determined by X-ray diffraction.