Electron neutrality

The passage of electrons from the metal to the electrolyte is not directly related to metal removal, but has an indirect connection due to the electron neutrality law ... 

The metal catalyst is not absolutely required for the aziridination reaction, and other positive nitrogen sources may also be used. After some years of optimization of the reactions of alkenes with positive nitrogen sources in the presence of bromine equivalents, Sharpless et al. reported the utility of chloramine-T in alkene aziridinations [24]. Electron-rich or electron-neutral alkenes react with the anhydrous chloramines and phenyltrimethylammonium tribromide in acetonitrile at ambient temperature, with allylic alcohols being particularly good substrates for the reaction (Schemes 4.18 and 4.19). 

Simple 1,3-dienes also undergo a thermal monocyclopropanation reaction with methoxy(alkyl)- and methoxy(aryl)carbene complexes of molybdenum and chromium [27]. The most complete study was carried out by Harvey and Lund and they showed that this process occurs with high levels of both regio-and diastereoselectivity. The chemical yield is significantly higher with molybdenum complexes [27a] (Scheme 7). Tri- and tetrasubstituted 1,3-dienes and 3-methylenecyclohexene (diene locked in an s-trans conformation) fail to react [28]. The monocyclopropanation of electronically neutral 1,3-dienes with non-heteroatom-stabilised carbene complexes has also been described [29]. 

Iminocarbene complexes of chromium and tungsten are useful isolable synthetic equivalents to nitrile ylides having the advantage that the range of 1,3-dipo-larophiles is not limited to electron-acceptor substrates and can be extended to electronically neutral as well as to electron-rich systems [56] (Scheme 18). 

S+1C] Cycloadducts have also been obtained in the reaction of alkenylcarbene complexes with electronically neutral 1,3-dienes by appropriate choice of the reaction conditions (see for comparison Sect. 2.6.4.4). Thus, performing the reaction in THF at 120 °C in a sealed flask the formal [4S+1C] cyclopentene derivative is generated in moderate yield [74a, 85] (Scheme 39). The key step... 

Barluenga J., Joglar J., Gonzales F. J. and Fustero S. Electronically Neutral 2-Aza-1,3-Dienes Are They Useful Intermediates in Organic Synthesis Synlett 1990 129 138... 

Second, in the collision term only electron-neutral collisions are considered, because RF plasmas are weakly ionized. The inelastic collisions considered are ionization, dissociation, excitation, and attachment (see also Table II). The crude... 

The condition of electron neutrality in case under consideration can be written as... 

Indoles, pyrroles, and carbazoles themselves are suitable substrates for palladium-catalyzed coupling with aryl halides. Initially, these reactions occurred readily with electron-poor aryl halides in the presence of palladium and DPPF, but reactions of unactivated aryl bromides were long, even at 120 °C. Complexes of sterically hindered alkylmonophosphines have been shown to be more active catalysts (Equation (25)). 8 102 103 In the presence of these more active catalysts, reactions of electron-poor or electron-rich aryl bromides and electron-poor or electron-neutral aryl chlorides occurred at 60-120 °C. Reactions catalyzed by complexes of most of the /-butylphosphines generated a mixture of 1- and 3-substituted indoles. In addition, 2- and 7-substituted indoles reacted with unhindered aryl halides at both the N1 and C3 positions. The 2-naphthyl di-t-butylphosphinobenzene ligand in Equation (25), however, generated a catalyst that formed predominantly the product from A-arylation in these cases. 

Finally, it was observed by Woodward and Back (1963) that in the radiolysis of propane at 800 torr pressure, the H2 yield decreased with the external field and also decreased upon decreasing the dose rate. Both effects are explainable on the assumption of a competition between the gas-phase electron neutralization and ionic neutralization at the wall. The latter process presumably is accompanied by at least a partial stabilization of the excited state produced. 

Clustering following the first ion-molecule reaction is apparently a reversible reaction. The equilibrium of this reaction is of some importance, as one can get two H atoms by the electron neutralization of HsO+. 

Ke>Ks In the undoped material a plateau is found over the middle part of the diagram where the dominant defects, [e ] and [h ], have equal concentrations. The point at which the solid is electronically neutral, when [e ] = [h ], occurs at the same partial pressure as when the solid is stoichiometric, [V J = [Vj J. 

A ternary reciprocal system is a system containing four components, but where these components are related through a reciprocal reaction. One example is the system LiCl-LiF-KCl-KF. Solid LiCl, LiF, KC1 and KF are highly ionic materials and take the rock salt crystal structure, in which the cations and anions are located on separate sub-lattices. It is therefore convenient to introduce ionic fractions (Xj) for each sub-lattice as discussed briefly in Section 3.1. The ionic fractions of the anions and cations are not independent since electron neutrality must be fulfilled ... 

RAMs packed in small cartridges are often used for online SPE of samples in biological matrixes. First developed by Boos et al. (1991), these alkyl-diol-silica (ADS) materials consist of large size particles (20 to 50 /.an compared to 3.5 to 5 /an for analytical columns) with hydrophilic electron-neutral surfaces that do not retain proteins and hydrophobic internal pore surfaces that allow only small molecules to enter and bind. 

The doso-duster containing two carbon atoms, i.e., o-, m- or p-dicarba-doso-dodecaborane C2B10H12, is electronically neutral (see Chapter 3.2). Therefore, the cages are thermally and chemically stable, and extremely hydrophobic. The C2Bio cages are advantageous for boron neutron capture therapy (BNCT) because of their high boron content and ease of chemical transformation. 

Unsaturated even-electron cations have been used in the gas phase to react with olefins, including dienes, in a way that characterizes their structure. In most cases, these ion/molecule reactions take place by [4 + 2] cycloadditions followed by specific elimination of even-electron neutrals. A most suitable instrumental setup for these studies are triple-quadrupole and pentaquadrupole mass spectrometers in which the ion/molecule addition reactions take place subsequent to the selection of the reagent ion. In most... 

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