Theoretical study of free radicals

The theoretical basis for the understanding of free radicals was first provided by G.N. Lewis in 1916. His clear recognition of the electron pair bond and the possibility of odd electron systems was heavily influenced by the work of pioneers such as Gomberg, Schlenk, and Wieland, who had showed 

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Theoretical studies of free-radical initiated cyclization of enediynes predicted that electron-deficient acetylenic substituents increases the Bergman cyclization barrier. The radical cyclization of enediynes containing electron-withdrawing substituents (such as acetyl and ethoxy-carbonyl groups) has been investigated. Heating a solution of l,2-bis(3-ethoxycarbonyl-l-butynyl)ethene 3.652 in the presence of stable radicals... 

A few words about the pattern of organization of this chapter. The theoretical studies are included in Section II. In Section VII some interesting chain reactions involving sulfonyl radicals are discussed, although often one of the propagation steps is treated earlier in Section IV or V. Finally, some general concepts of free radical chemistry are introduced at appropriate points throughout the review without any reference. 

Oxidative chain reactions of organic compounds are current targets of theoretical and experimental study. The kinetic theory of collisions has influenced research on liquid-phase oxidation. This has led to determining rate constants for chain initiation, branching, extension, and rupture and to establishing the influence of solvent, vessel wall, and other factors in the mechanism of individual reactions. Research on liquid-phase oxidation has led to studies on free radical mechanisms and the role of peroxides in their formation. 

The study of the reactions of the simple free radicals begun by Bodenstein and Lind in 1906 on the kinetics of gas phase reactions showed that the reactions of H2 with CI2 and Bt2 were complex processes/ and a radical chain mechanism for these reactions (equations 14-18) was proposed in 1919 by Christiansen, Herzfeld, and Polanyi/ The theoretical basis for understanding these reactions in terms of free radicals was presented by G.N. Lewis in 1916, with the theory of the electron pair bond, and free radicals, or odd molecules / Further studies on chain reactions including the extension to explosions in gaseous systems were made by Hinshelwood and by Semenovwho shared the Nobel Prize in 1956. 

The process of obtaining alkyl sulphonate in an autoclave with a mixer has been studied. Basic reagents were water solution of sodium hydrosulfite 36-38% and industrial olefin fractions at 240-320 °C. NaN03 and oxygen from air were used as initiators of the reaction of free radicals. System factors are x, reaction time, h x2 temperature of reaction, °C x3 mole ratio of sodium hydrosulfite and olefin x3 mole ratio of NaN03 and olefin x5 volume ratio of N-propanol and olefin. System response is a yield of alkyl sulfonate as a per cent of theoretical yield. FRFE design... 

The process of obtaining alkylsulfonate, used as raw material for synthetic products for washing, has been researched. Basic reagents are a water solution of sodium bisulfate and olefins. NaN03 and oxygen from air were used as initiators in reaction of free radicals. Based on previous studies, these factors were chosen xj-reaction time, h x2-reaction temperature, °C x3-mole ratio NaHS03 and olefins, [1] x4-mole ratio NaN03 and olefins, [1] and x5-volume ratio of N-propanol and olefins, [1], The yield of alkylsulfonate in per cent of theoretical yield has been determined as the... 

The halogenation reaction of ethylene has been modeled by many researchers [170, 172-176], For chlorination in apolar solvents (or in the gas phase), the formation of two radical species requires the use of flexible CASSCF and MRCI electronic structure methods, and such calculations have been reported by Kurosaki [172], In aqueous solution, Kurosaki has used a mixed discrete-continuum model to show that the reaction proceeds through an ionic mechanism [174], The bromination reaction has also received attention [169,170], However, only very recently was a reliable theoretical study of the ionic transition state using PCM/MP2 liquid-phase optimization reported by Cammi et al. [176], These authors calculated that the free energy of activation for the ionic bromination of the ethylene in aqueous solution is 8.2 kcalmol-1, in good agreement with the experimental value of 10 kcalmol-1. 

Theoretical Aspects. Ultraviolet light-cured inks are cured by free radical-initiated vinyl addition polymerization. The photochemical initiation of vinyl polymerization has been the subject of many investigations dating back more than 30 years, to the first systematic studies of polymerization kinetics. Photochemical initiation offered a reproducible source of radicals that is not dependent upon temperature as is the thermal decomposition of free radical initiators. However, despite these early studies of its mechanism and kinetics, only recently has photochemical initiation become of practical interest, mainly because of the recent development of ultraviolet lamps suitable for production curing of printing inks and coatings. 

The differences in relative activity of these compounds may be related to effects various constituents have on the ability to form highly reactive free radicals. A study which could help elucidate the actual mechanism of action of these compounds would be to examine (theoretically or experimentally) their ability to form radicals. If they express their herbicidal activity via this mechanism, then the energy and reactivity of free radical formation should show a positive correlation with the relative activity differences found in an intrinsic bioassay. For this purpose, the midpoint redox potential of the one-electron transfer couple DPE-NO2 DPE-N02 needs to be determined. This could be accomplished using such techniques as polarography or cyclic voltometry. It may also be feasible to study these reactions in darkness through the use of artificial electron... 

In this chapter, we review the theoretical work on thermal FP. We begin with a derivation of a base mathematical model which governs propagation of free-radical polymerization waves. We demonstrate that this model reduces in a limiting case to the famous gasless combustion (GC) model, which has been extensively studied in the context of SHS. We discuss some theoretical approaches to the simpler GC model and then apply them to the base model of free-radical FP. Some extensions of the base model are also discussed. 

R. Erickson (a) Electron magnetic resonance of free radicals. Theoretical and experimental EPR, ENDOR and ESEEM studies of radicals in single crystal and disordered solids . Ph. D thesis, Linkbping studies in science and technology. Dissertation No. 391 (1995) (b) Chem. Phys. 202, 263 (1996). 

Theoretical aspects of NMR of free radicals containing spin-1/2 nuclei have been thoroughly discussed in the literature.29 Extension of these studies to free radicals containing quadrupolar nuclei (i.e., nuclei with nuclear spin 1) is relatively straightforward, especially in the solution phase with which we are mainly concerned here. The quadrupolar interaction, however, does lead to fast relaxation and hence broadens the NMR signals. We make a further assumption that the electronic Zeeman term, giSH, is much... 

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