reactius

Reactius is a fictional chemical species invoked in theoretical chemistry to explore the behavior of highly reactive intermediates in complex reaction networks. The name combines the root 'react' with the Latin suffix -ius, and it has no confirmed physical existence in laboratory experiments.

In schematic models, reactius is characterized by a very short lifetime and by potent reactivity toward a wide range of substrates. It is portrayed as species that can be formed transiently from various precursor molecules under extreme conditions or via photochemical or radical pathways in simulations. Because it is a conceptual construct rather than an observed substance, its exact structure is left unspecified and may vary between models.

Properties attributed to reactius are deliberately schematic: high reactivity, ambiguous or model-dependent electronic structure, and a propensity to undergo rapid branching, yielding multiple products. The lack of a fixed composition allows it to serve as a neutral placeholder for examining kinetic competition and energy disposal in reaction networks.

Uses of the concept include teaching chemical kinetics, testing numerical methods for stiff systems, and illustrating how transient species affect selectivity and yield in proposed pathways. As a tool in pedagogy, reactius helps demonstrate the influence of intermediate lifetimes and competing channels on observed outcomes.

See also: reactive intermediate, transition state theory, chemical kinetics, computational chemistry.