The reaction mechanism is the step-by-step sequence of events in a chemical reaction. It includes breaking chemical bonds, producingtransition state intermediates, and making chemical bonds. In this unit, you will start with an overview of the functional groups of organic molecules. Next, you will study the mechanisms of nucleophilic substitution, electrophilic addition, condensation, elimination, and redox reactions. The goal is to highlight the fact that these reactions go forward only if the reactants meet specific structural requirements.