intramolekulare

The term intramolekulare (English: intramolecular) describes processes, reactions, or interactions that occur within a single molecule. The concept is used across chemistry, biochemistry, and related fields to distinguish internal events from interactions between separate molecules (intermolecular).

In reaction kinetics, intramolecular steps often benefit from a high effective concentration of reactive groups inside the same molecule, which can lower the barrier for bond formation or cleavage. This preorganization reduces the entropy loss that would accompany bimolecular collisions, sometimes accelerating the reaction despite a larger intrinsic activation energy. However, the rate can still be limited by conformational changes needed to bring reactive sites into proximity.

Common examples include intramolecular cyclizations that form rings, such as lactones or lactams, and intramolecular proton transfers or hydrogen-bond networks that stabilize certain conformations. Sigmatropic and other rearrangements can proceed intramolecularly within a single molecule. Intramolecular processes also influence spectroscopy and physical properties through specific intramolecular interactions, such as hydrogen bonding or vibrational coupling.

Understanding intramolecular effects is important in synthesis, where preorganized substrates guide selectivity, in biochemistry for enzyme mechanisms and folding, and in materials science for polymer architecture and molecular sensors.