A foundation-level course is described that integrates material related to reactivity in organic, inorganic, and biochemistry. Designed for second-year students, the course serves majors in chemistry, biochemistry, and biology, as well as prehealth-professions students. Building on an earlier course that developed concepts of nucleophiles and electrophiles in organic carbonyl chemistry and coordination compounds, Reactivity II explores the concept of mechanistic alternatives in substitution reactions of alkyl halides and transition metal complexes. Kinetics is introduced as a diagnostic tool for understanding mechanisms, and is extended to the study of enzyme-catalyzed reactions. An introduction to the reactivity of alkenes and aromatics rounds out students' understanding of reactions involving electrophiles and nucleophiles.