Reagents used in chemical reactions are substances that participate directly in bringing about chemical transformation, either by providing necessary reactants or by facilitating the reaction through specific chemical properties. An ideal reagent should exhibit high reactivity and selectivity so that the desired product is formed efficiently without generating unwanted by-products. It should be stable under reaction conditions, easy to handle, and compatible with commonly used solvents or reaction media. Reagents are often required to function under mild temperature and pressure conditions to minimize energy consumption. In addition, good reagents allow reactions to proceed with high yield and purity, reducing the need for extensive purification steps.