unreacted

Unreacted is a term used in chemistry and related fields to describe material that has not participated in a chemical reaction or has not been converted to the desired products. It denotes substances that remain in a mixture after a reaction has occurred. In stoichiometric calculations, theoretical yield assumes complete conversion, while the actual yield accounts for unreacted material.

In practical reactions, incomplete conversion can leave some reactants unreacted at the end of a process. This can happen due to kinetic limitations, equilibrium constraints, mass transfer issues, or competing side reactions. The extent of conversion is a key parameter in reactor design and process optimization, influencing efficiency, cost, and waste generation.

In polymer chemistry and materials science, unreacted monomers or functional groups may remain in a material after curing or polymerization. Residual monomers can affect mechanical properties, color, odor, and safety, and may require post-processing steps such as washing, drying, purification, or post-curing to reduce levels below acceptable thresholds. Regulatory and quality standards often specify limits for residual unreacted species.

Detection and management of unreacted material rely on analytical techniques such as gas chromatography, high-performance liquid chromatography, infrared or nuclear magnetic resonance spectroscopy, and gravimetric methods. Practices to minimize unreacted content include process optimization to improve conversion, recycling or reclaiming unreacted feed, distillation, or thorough purification of final products.