termolekyylireaktio

Termolekyylireaktio, or thermal decomposition, describes a chemical transformation in which a single reactant molecule splits into two or more products upon absorption of heat. The process requires sufficient thermal energy to overcome the activation barrier associated with bond cleavage, and the reaction is typically exothermic or endothermic depending on the stability of the products relative to the reactant.

Thermolysis is classified according to the nature of the bonds broken. Homolytic cleavage generates free radicals when covalent bonds dissociate evenly, whereas heterolytic cleavage yields ions or zwitterions when the bonding electrons favor one fragment. Common mechanisms include unimolecular decomposition, which follows first‑order kinetics, and bimolecular processes where two molecules interact to form a transition state before fragmentation.

Typical examples involve organic molecules such as the pyrolysis of cellulose to produce levoglucosan, the decomposition of ammonia at high temperatures to give diatomic nitrogen and hydrogen, and the thermal cracking of hydrocarbons to generate lighter alkanes and alkenes. In industrial contexts, termolekyylireaktiot are exploited for polymer recycling, waste treatment, and the production of advanced materials. In atmospheric chemistry, thermal breakdown of pollutants contributes to the formation of secondary organic aerosols.

The rate of thermal decomposition is strongly temperature-dependent, often described by the Arrhenius expression k = A exp(−Ea/RT), where Ea is the activation energy. Activation energy can be assessed experimentally through kinetic studies or computationally via quantum‑chemical calculations. Understanding termolekyylireaktio mechanisms aids in designing catalysts that lower activation barriers, stabilizing intermediates, or steering product selectivity toward desired outcomes.