1. A chemical reaction in which two or more unsaturated molecules combine to form a cyclic compound, typically involving the rearrangement of electrons and bonds.
Usage: chemistry; technical term commonly used in organic chemistry

Examples

• The Diels-Alder reaction is one of the most important cycloaddition reactions in organic synthesis.
• In a cycloaddition, two π-bonds break and two new σ-bonds form to create a ring structure.
• Cycloaddition reactions are widely used in pharmaceutical manufacturing to build complex molecular structures.
• The [4+2] cycloaddition between a diene and a dienophile produces a six-membered ring.
• Photochemical cycloaddition can occur when molecules are exposed to ultraviolet light.