unimolekylære

Unimolekylære refers to a chemical reaction that involves only a single molecule as a reactant. In such a reaction, the single molecule undergoes a transformation, such as rearrangement or decomposition, without interacting with any other molecules in the rate-determining step. The rate of a unimolecular reaction is directly proportional to the concentration of that single reactant molecule. This means that if the concentration of the reactant is doubled, the reaction rate will also double.

Unimolecular reactions are often observed in the gas phase, where molecules are relatively far apart and the probability of bimolecular collisions (reactions involving two molecules) is reduced. Examples include the isomerization of cyclopropane to propene or the decomposition of certain unstable molecules. The mechanism of a unimolecular reaction typically involves an initial activation step, where the molecule gains enough energy to undergo the transformation. This activation can occur through collisions with other molecules (Lindemann mechanism) or through internal energy redistribution within the molecule itself. Understanding unimolecular reactions is crucial in various fields, including atmospheric chemistry and the study of reaction kinetics.