Bimolekär

Bimolekär is a Swedish term used in chemistry to describe processes, reactions, or mechanisms that involve two molecules as active participants. The word is related to the root bi- meaning two and molekyl, and it is closely connected to the more common form bimolekylär. In practice, bimolekär is often used to distinguish two-molecule processes from unimolekär processes, which involve only a single molecule, and from larger, multi-molecular steps.

In reaction kinetics, bimolekär processes are typically characterized by rate laws that depend on the concentrations of two reacting species. A classic example is a bimolecular reaction of the form A + B → products, where the rate is proportional to the product [A][B]. This contrasts with unimolekär reactions, where the rate depends mainly on the concentration of a single reactant. The concept is central to collision theory and transition-state theory, which describe how two molecules must collide with sufficient energy and proper orientation to react.

Bimolekär processes are relevant across chemistry and biochemistry, including organic synthesis, catalysis, and enzyme-mediated reactions where two molecules interact to form a new intermediate or proceed to products. In biophysics, bimolekär interactions can describe binding events between two molecular partners, such as receptor-ligand encounters or dimerization steps that are prerequisites for activity.

The term is used in educational and scientific texts to categorize reaction types and to aid in the analysis of mechanisms, rate laws, and experimental design. See also unimolekär and multi-molekylära processes.