Thermal kinetic energ

Alkenes. The available kinetic and mechanistic data show that under atmospheric conditions the reaction of HO radicals with alkenes proceeds predominantly via addition of the HO radical to the carbon-carbon double bond(s) [30]. The energized HO-adducts which result are rapidly thermalized to yield HO-substituted alkyl radicals which, in turn, undergo subsequent free-radical reactions leading to the formation of molecular products. Thus, the possible reactions in the HO-inidated oxidation are, in many respects, analogous to those of alkyl radicals described in the preceding section. Product studies on these reactions have mainly been made by the FTIR method [109-112]. 

It has been known since the start of the 20th century that thermal unimolecu-lar reactions obey first-order kinetics, and for some time this observation posed a problem. If molecules require energization to react, and collisional energization is a second-order process, how can the kinetics be first-order ... 

At the low pressures used in many laboratory kinetics experiments, the rate of formation of allyl radicals by this two-step pathway will be much higher than one would compute if one assumed that the energized intermediate CH3C (OEt)OCH2CFlCH2 was in thermal equilibrium with the bath gas the rate for... 

Energy is conserved. It may be converted from one form to another, say from potential to kinetic energy, but the total amount of energy in the universe is constant. The energy that an exothermic reaction releases always goes somewhere in the environment, usually in the form of thermal energ) (heat). 

The study of dynamics allows us to raise additional questions, questions that do not quite make sense when we study the net change, at or near equilibrium, in the bulk. For example, we can wonder if exciting vibrational motion in either or both reactant diatomic molecules will make the CI2 + Br2 four-center reaction proceed more rapidly. In bulk chemical kinetics, when the reactants are intentionally arranged to be in thermal equilibrium, a particular mode cannot be energized preferentially. To learn about a selective role of internal energy in promoting a reaction it is necessary to work under non-equilibrium conditions. ... 

In this chapter we describe the estimation and interpretation of rate coefficients for thermal dissociation, isomerization, and recombination reactions. While such reactions are only a small fraction of the elementary reactions of combustion mechanisms, some of them do play essential roles. Their kinetic behavior is governed by the competition of unimolecular chemical changes in molecular structure with bimolecular physical collisional energization and deenergization processes. 

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