Radical ion electron

Active particles, free atoms, radicals, ions, electrons, and excited particles produced in the field of high-energy radiation or in electric discharge interact with various chemical compounds. This interaction is accompanied by a variety of homogeneous and heterogeneous physical-chemical processes. 

Species with electron deficiency (e.g. carbocations), unpaired electrons (e.g. radicals, radical ions), electron excess (e.g. carbanions), or those with unusual oxidation states (e.g. metal complexes with low- or high-valent central atoms) are produced at the electrode. Electrochemical generation of such intermediates may be advantageous because of the mild reaction conditions employed (room temperature. 

Mayeda EA, Bard AJ. The production of singlet oxygen in electrogenerated radical ion electron transfer reaction. / Am Chem Soc 1973 95 6223-26. 

Ignasiak, T., Kemp-Jones, A. V. and Strausz, 0. P., "The Molecular Structure of Athabasca Asphaltenes. Cleavage of the Carbon-Sulfur Bonds by Radical Ion Electron Transfer Reactions," J. Org. Chem., 1977, 42(2), 312-320. 

In a discharge plasma the polymer sample is in a complex flow of energetic species, like radicals, ions, electrons and VUV and, as it was pointed above, it is impossible to study separately the reactions between the surface and each species. A model gas phase can be an electron, an ion or a neutral beam (with a well-defined current density and average energy), UV radiation or a remote discharge plasma. Since the interaction of UV and particle beams with polyolefins are presented in other sections of this chapter, here some new results about remote discharge plasmas are pointed out. 

Sekiguchi S, Kobori Y, Akiyama K and Tero-Kubota S 1998 Marcus free energy dependence of the sign of exchange interactions in radical ion pairs generated by photoinduced electron transfer reactions J. Am. Chem. Soc. 120 1325-6... 

Gould I R, Ege D, Mattes S L and Farid S 1987 Return electron transfer with geminate radical ion pairs - observation of the Marcus inverted region J. Am. Chem. Soc. 109 3794-6... 

Free Radicals. In the formula of a polyatomic radical an unpaired electron(s) is(are) indicated by a dot placed as a right superscript to the parentheses (or square bracket for coordination compounds). In radical ions the dot precedes the charge. In structural formulas, the dot may be placed to indicate the location of the unpaired electron(s). 

Radical ion. An ion containing an unpaired electron that is thus both an ion and a free radical. The presence of the odd electron is denoted by placing a dot alongside the symbol for the charge. Thus, and SF are radical ions. 

The mechanism of chemiluminescence is still being studied and most mechanistic interpretations should be regarded as tentative. Nevertheless, most chemiluminescent reactions can be classified into (/) peroxide decomposition, including biolurninescence and peroxyoxalate chemiluminescence (2) singlet oxygen chemiluminescence and (J) ion radical or electron-transfer chemiluminescence, which includes electrochemiluminescence. 

Electron-transfer reactions producing triplet excited states can be diagnosed by a substantial increase in luminescence intensity produced by a magnetic field (170). The intensity increases because the magnetic field reduces quenching of the triplet by radical ions (157). 

The added electron is delocalized on the monovalent radical ion to which it is reduced (3). There is no general agreement on the molecular representation of the reduced stmcture. Various other viologen compounds have been mentioned (9,12). Even a polymeric electrochromic device (15) has been made, though the penalty for polymerization is a loss in device speed. Methylviologen dichloride [1910-42-5] was dissolved in hydrated... 

The dithionite ion has a remarkable eclipsed stmcture of approximate C2v symmetry (Fig. 15.32b). The extraordinarily long S-S distance (239 pm) and the almost parallel SO2 planes (dihedral angle 30°) are other unusual features. Electron-spin-resonance studies have shown the presence of the S02 radical ion in solution ( 300ppm), suggesting the establishment of a monomer-dimer equilibrium 8204 ... 

Flames are also plasmas, characterized by electron densities of about 10 /cm and electron energies of about 0.5 eV. Many excited species are present in the flame, namely free radicals, ions, excited atoms and molecules, and electrons [43]. Excited species that have been observed include O, OH, NH, NO, and CH [44]. 

For PPV-imine and PPV-ether the oxidation potential, measured by cyclic voltammetry using Ag/AgCl as a reference are ,M.=0.8 eV and 0.92 eV, respectively. By adopting the values 4.6 eV and 4.8 eV for the work functions of a Ag/AgCl and an 1TO electrode, respectively, one arrives at zero field injection barriers of 0.4 and 0.55 eV. These values represent lower bounds because cyclic voltammetry is carried out in polar solvents in which the stabilization cncigy of radical ions exceeds that in a polymer film, where only electronic polarization takes place. E x values for LPPP and PPPV are not available but in theory they should exceed those of PPV-imine and PPV-ether. 

The mole is the amount of substance which contains as many elementary units as there are atoms in 0.012 kilogram of carbon-12. The elementary unit must be specified and may be an atom, a molecule, an ion, a radical, an electron or other particle or a specified group of such particles. ... 

A different situation arises in the initiation reaction resulting from an electron transfer to a monomer. Such an initiation has been discussed recently42 43 and leads to a species containing one extra electron which behaves like a radical ion. It has been pointed out that the extra electron may be conveniently ascribed to the lowest unoccupied n orbital of the monomeric molecule (see Figure I), a... 

The electron affinity of radicals is considerably greater than the electron affinity of monomers, hence in the presence of monomer" ions, or in the presence of an excess of the primary electron donors, the dimeric radical ions are rapidly converted into dimeric diions,... 

Let us consider the conditions which favor the formation and survival of the dimeric and polymeric radical ions. This might be achieved by keeping the concentration of monomer high, the concentration of monomer" ions low and by removing the radical ions as rapidly as possible from the zone containing the primary electron donors. Moreover, since the radical ions dimerize, their average life time increases as their concentration decreases. The following experiment should probably produce the best results. 

The transfer of an electron from a photoexcited donor molecule (D) to an acceptor molecule (A) to generate a highly reactive radical ion pair is the most fundamental photochemical reaction, and it can be generally expressed as... 

Radical ion (odd electron ion) An ion containing an unpaired electron that is both a radical and an ion. 

In the case of the 2,1-naphthoquinone diazide Zeller (1975a) was able to demonstrate clearly that the electron impact induced loss of N2, CO, and H is a stepwise process. The question of the possible involvement of a naphthooxirene intermediate (4.25) was clearly answered by mass spectrometry of the l-13C-2,1-naphthoquinone diazide (4.24). The [M - N2 - CO]+ radical ion (4.26) does not contain 13C, and therefore no naphthooxirene is formed (Scheme 4-4). 

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