Steric effects in organic chemistry refer to the influence of the spatial arrangement of atoms within a molecule on its reactivity and stability. These effects arise when atoms or groups of atoms are in close proximity, leading to repulsion or hindrance that can affect chemical reactions. For example, bulky groups can slow down reactions by obstructing access to reactive sites, impacting the overall reaction rate. Understanding steric effects is crucial for predicting the behavior of molecules in various chemical processes. They play a significant role in determining the selectivity of reactions, such as in nucleophilic substitutions or catalysis, where the size and shape of reactants can influence the outcome.