Many measurement methods lead only to the determination of the energies. that the boundary of the hole is stress-free, and that b and c are small in. They are directly related to the bond dissociation energies of the molecular entity from which the radicals are formed and is a convenient marker for molecular stability or reactivity.
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Much effort has been devoted to determining the enthalpies of free radicals (4,5). In order to determine the property of a radical the thermodynamic properties of the other compounds for the reaction must be known and if reactions are carried out at temperatures different than 298 K heat capacity corrections must be made. Substituting back into Eq 1 then leads to a determination of the entropy. [31 This is known as the second law method. This can be expressed as, AF=AH-TAS=-RTln Kp /d(l/T)=-AH/R. The thermodynamic stability of any compound can most conveniently be expressed in a quantitative sense in terms of its free energy or equilibrium constant of formation. Quantitative understanding of the temporal behavior of such processes depends on knowledge of the thermodynamic and kinetic properties of the radicals. BACKGROUND The reactions of hydrocarbons in the gas phase and non-polar media frequently proceed through free radical mechanisms. Finally, thermodynamic and kinetic data bearing on the stability of the radicals will be summarized. This will be followed by a survey of some of the problems and controversies regarding correct values.
A number of the important issues dealing with the accurate determination of these properties will be discussed. We will begin with some definitions regarding thermodynamic and kinetic stability and general comments justifymg our interest. \ Thermal Stability of Hydrocarbon Radicals Wing Tsang National Institute of Standdds and Technology Gaithersburg, MD 20899 ABSTRACT This paper reviews the present state of knowledge regarding the stability of hydrocarbon radicals.
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