Electron transfer, from ethylene

According to RHF 4-3IG calculations the odd electron is practically fully localized at the F atom, while changes affecting charges in ethylene are insignificant. However, the UHF calculations indicate considerable polarization of the charges in ethylene arising on account of the j -spin electron transfer from ethylene to fluorine and a decrease in electron density at the —C2 bond. The probability of the a-electron transfer is low. 

In a report on the electron transfer between dye/hole transport electrolyte, the electron transfer rate from redox electrolytic solution (0.3 M KI and 0.03 M I2 ethylene carbonate/propylene carbonate (1 1) solution) to oxidized state of Dye 2 was determined to be 110 nsec based on the lifetime of the Dye 2 cation.41) It is much faster (by an order of 103 fold) than the back electron-transfer from Ti02 to oxidized Dye 2. 

Reductive dechlorination of chlorinated solvents in the ZVI system is a surface-mediated process. Adsorption of the chlorinated compounds takes place prior to the reduction, but the overall rate of reduction is limited by the electron transfer from the surface to the chlorinated compounds. The adsorption can occur on either reactive or nonreactive sites, while the reduction rate is directly proportional to the amount adsorbed onto the reactive sites. The proportion adsorbed onto reactive sites to the nonreactive sites is related to the nature of chlorinated compounds. Higher chlorinated ethylenes such as PCE and TCE are likely to have a larger portion going to the nonreactive sites compared to less chlorinated ethylenes like vinyl chloride. A two-site model incorporating the known observations related to the ZVI system has been developed and such a model can be applied to explain the adsorption and reduction of chlorinated solvents in the presence of competing coadsorbates. 

Fig. 6. Perrin quenching radii, Rq, [43] vs. variations of the free energy, — AG°, of electron transfer from the excited donor molecule to the acceptor molecule for donor-acceptor pairs in vitreous rra .y-1.5-decalindiol. l.Rubrene + Ar,jV-dicthylaniline (DEA) 2, rubrene + N,N, V, Ar -tetramethyl-p-phcnylenediamine (TMPD) 3, rubrene + tetrakis (dimethylamino)-ethylene 4, tetracene + DEA 5, tetracene + TMPD 6, 9, 10-dinaphthylanthracene + DEA 7, 9, 10-dinaphthylanthracene + TMPD 8, perylene + DEA 9, perylene + TMPD 10, 9-methylanthracene + TMPD 11, 9, 10-diphenylanthracene + TMPD 12, coronene + TMPD 13, benzofghi] perylene + TMPD 14, fluoranthene + DEA 15, acridine + DEA...

It is well known that the flavin adenine dinucleotide redox centers of many oxidases are electrically inaccessible due to the insulating effect of the surrounding protein thus, direct electron transfer from the reduced enzyme to a conventional electrode is negligible. In the present work, a variety of polymeric materials have been developed which can facilitate a flow of electrons from the flavin redox centers of oxidases to an electrode. Highly flexible siloxane and ethylene oxide polymers containing covalently attached redox moieties, such as ferrocene, are shown to be capable of rapidly re-oxidizing the reduced flavoenzyme. 

It is clear from these results that the ability of the redox polymers to mediate electron transfer from reduced choline oxidase is dependent upon the structure of the polymer backbone. The trend in mediating efficiency is qualitatively the same as that found for the glucose sensors siloxane-ethylene oxide branch polymer > poly(ethylene oxide) > poly(siloxane). 

The electron transfer from the two bis(amido) ligands toward the electrophilic Zr atom in complexes 12 and 13 is ascertained by the chemical shifts of the ethylene groups. A similar trend in 12 is observed for the Me3Si groups. These results, compared with those for complex 11, show a similar electronic environment between the Cp and the bis(amido) ancillary ligands. 

Alternatively, Lewis acids such as SbCl5 may initiate oligomerization directly by electron transfer from extremely reactive alkenes such as 1,1-diphenylethylene and 1,1 -di(p-methoxyphenyl)ethylene [28,143,144]. The dimeric tail-to-tail carbenium ion of 1,1-diphenylethylene shown in Eq. (32) was observed, and its formation explained by a radical cation intermediate. Because 1,1-diarylethylenes can not polymerize, only oligomerization was observed. 

Divalent samarium complexes can also catalyze ethylene polymerization, initially through one-electron transfer from the Sm(II) species to an ethylene molecule to form a Sm(III)-carbon bond, which is the active intermediate that induces ethylene polymerization. The less reducing divalent organometallic ytterbium and europium complexes are generally inert [143]. 

One of these bonds is ir-bond. It is formed by electron transfer from ligand to metal. Depending on their nature, such ligands can contribute a variable number of 7r-electrons two (ethylene), three (the 7r-allyl group), four (cyclobutadiene), five (the cyclopentadienyl group), six (benzene), etc. (see Figure 1). It means that 7r-bond exist between... 

According to ref the Ti—C bond is mainly of covalent character with Ti —C polarization. The length of the titanium-carbon bond, when passing from the methyl to the ethyl complex, changes insignificantly, and it can be supposed that the properties of this bond are independent of the chain length. In the formation of a rt-complex an appreciable proportion of the electron density (as 0.25 e) is transferred from ethylene to the titanium ion. 

Two examples of 1,4-addition to the naphthalene ring have been reported. In one. the substituent effects upon the reaction between the triplet excited state of 1-acetyinaphthalene and variously substituted alkenes has been examined. while in the other, the 1.4-addition of a-methyl styrene and of 1,1-dlphenyl ethylene to the phthallmide (125) is shown to proceed by electron transfer from the alkene to the excited state of the phthallmide. The azaindone (126), which is Isoelectronic with naphthalene, also forms addition products when Irradiated with stilbene. The addition products are assigned the structures... 

With such reactions, it is quite obvious that deprotonation should be faster than the nucleophilic attack, in order to observe a regioselective substitution. In the equation written above, the ethylenic double bond plays the role of an electrophore (electron transfer from the HOMO of the unsaturated system). The reactivity of unsaturated systems is illustrated by the oxidation of cycloheptatrien [43] in methanol when the methoxylation was achieved in good yield. 

Two kinetic studies of electron-transfer from carbanions to aromatic acceptors will be discussed. The reversible interaction of anthracene, An, with the dimeric-dianions of 1,1-diphenyl ethylene, Na+, DD, Na+, leads to an equilibrium mixture1035,... 

The mechanism accounting for the formation of ethylene from methional consists of electron transfer from the sulfur atom of methional to the pho-toactivated FMN (FMN ), followed by a nucleophilic attack by OH on the aldehyde group and a concerted elimination of the methylsulfinium group ... 

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