Formation of anions

Gas phase anions may be generated by electron impact via one of the following three processes  

Most organic compounds do not have a sufficiently high ionization cross-section for a workable yield of anions to be obtained. Most organic anions are therefore generated via ion/molecule reactions of organic molecules with 

The gas-phase acidities, defined as the enthalpy change for reaction (5), of 

Gas phase acidity values in kj mol 1 for the reaction RH - R + H+ of some selected molecules at 298 K 

4 Some basic aspects of gas-phase ion/molecule reactions 

F is the force, and q2 are the charges, and r is the distance between them (in this case, the distance between the nuclei of the two ions). It can also be shown that the potential energy, V, of the system is given by 

is a proportionality constant, whose value is 1.389 x 10 kj pm/mol if the charges are expressed in units of electron charge. 

Black lines show attractive forces between (1st) nearest neighbors. 

Blue lines show attractive forces with 3rd nearest neighbors. 

Red lines show repulsive forces with 2nd nearest neighbors. 

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Most enones are reduced to anion radicals by organo cuprates. It is likely, that this reaction is connected with the alkylation. Both the formation of anion radicals and of conjugate adducts are not observed, when the redox potential of the enone becomes too negative (H.O. House, 1976). 

The mechanism involves the formation of anion 3 from ester 1 by reaction with base ... 

The extraction of metals by liquid amines has been widely investigated and depends on the formation of anionic complexes of the metals in aqueous solution. Such applications are illustrated by the use of Amberlite LA.l for extraction of zirconium and hafnium from hydrochloric acid solutions, and the use of liquid amines for extraction of uranium from sulphuric acid solutions.42,43... 

In contrast to bilateral triple-ion formation, unilateral triple-ion formation may also occur in solvents of high permittivity, when ion-pair association is increased by noncoulombic specific ion-ion interactions in solvents of low basicity such as PC or AN. Exclusive formation of anionic tripleions [A-C+A-] ", is observed in these solvents when large organic molecular anions A interact with small cations such as Li + or H+. For example, in contrast to lithium acetate in DMSO [97], where ion association is moderate, ion association as well as unilateral triple-ion formation is observed in the solvent PC [105] due to the much lower basicity of this solvent, (see Table 2)... 

In the presence of mineral phases containing anions that would form sparingly soluble compounds (e.g. POt - and F for the lower oxidation states) an enhanced plutonium uptake due to chemisorption can be expected (57). For plutonium in the higher oxidation states the formation of anionic carbonate complexes would drastically reduce the sorption on e.g oxide and silicate surfaces. 

While trifluoro and other halosilanes function by increased electrophilicity at silicon, nucleophilic reactivity of allylic silanes can be enhanced by formation of anionic adducts (silicates). Reaction of allylic silanes with aldehydes and ketones can... 

A common feature of metal atoms is that they are generally larger in size in comparison with nonmetal atoms. A characteristic of nonmetals is that their atoms have the ability to attach electrons to themselves, leading to the formation of anions. The opposite is true for the metals and as told they alter to cationic forms when their removable electrons leave them. 

The electrochemistry of a range of Ni(n) porphyrins and chlorins has been investigated. All complexes are reduced by a similar one-electron mechanism which appears to involve the formation of anion radicals (Chang, Malinski, Ulman Kadish, 1984). 

Type II intensity increased upon surface reduction due to the formation of anion vacancies. 

Conesa373 modeled the surfaces and defects on ceria, and based on computer simulations, determined the relative stabilities of surfaces (111) > (110) > (211) > (100). Although the formation of anion vacancy defects was suggested to be more difficult to form on the more stable (111) surface, he indicated that anion vacancy pairs, important for 02 uptake and release processes, were easiest to form on the ceria (111) surface. 

Ligand Exchange Surface Complex Formation of Anions and Weak Acids... 

The problem of measuring the thermodynamic properties of aqueous transition metal ions above 100 C has also received some attention with studies on Fe + complexing with Cl (46), Br (47) and SO - (48) up to 150°C and the formation of anionic hydroxy complexes of Pb2+ up to 300°C (49). 

Hajhium. It is very similar to Zr. The best solvent is HF the formation of anionic fluoro-complexes is, also in this case, determinant in the stabilization of the solution. 

Like the formation of anionic EGBs by direct reduction of weak nitrogen or oxygen... 

However, cobalt complexes, treated with a tenfold excess of Grignard or lithium reagents lead to the formation of anionic species (Scheme 5) ... 

We have discussed the direct formation of anions by reaction of silyl- or germyl-lithiums with metal carbonyls (cf. Sect. 2.12) ... 

Irradiation accelerates the reactions of Scheme 4.1, and the substitution products are formed in 70-80% yields. Acceptors of radicals (e.g., di-tert-butylnitroxyl) or electrons (e.g., m-dinitro-benzene [DNB]) completely inhibit the snbstitution even if the acceptors are added to the reaction mixture in small amonnts. The mentioned snbstitution reactions do not take place when no cyano groups are present in the initial a-phenylsnlphonyl cumene. Hence, the cyano groups send the reaction via the ion-radical pathway. Like the nitro gronp, the cyano group promotes the formation of anion-radical, which originates on one-electron transfer from the thiophenolate or malonate ions to the substrate. 

Sodium methylate acting on 2-chloroanthraquinone substitutes the methoxy group for chlorine and produces anion-radicals of the substrate (Shternshis et al. 1973). The study of kinetics has demonstrated that the amount of substrate anion-radical hrst increases and then sharply decreases. The inhibitor (p-BQ) decelerates the formation of anion-radicals. The rate of formation of 2-methoxy-anthraquinone also decreases. If anion-radicals are produced on the side pathway, the rate of formation of the end product on introduction of the inhibitor should not have decreased. Moreover, it should even rise because oxidation of anion-radicals regenerates uncharged molecules of the substrate. Hence, the anion-radical mechanism controls this reaction. 

As described, other nucleophilic reactions in the anthraquinone series also involve the production of anion-radicals. These reactions are as follows Hydroxylation of 9,10-anthraquinone-2-sulfonic acid (Fomin and Gurdzhiyan 1978) hydroxylation, alkoxylation, and cyanation in the homoaromatic ring of 9,10-anthraquinone condensed with 2,1,5-oxadiazole ring at positions 1 and 2 (Gorelik and Puchkova 1969). These studies suggest that one-electron reduction of quinone proceeds in parallel to the main nucleophilic reaction. The concentration of anthraquinone-2-sulfonate anion-radicals, for example, becomes independent of the duration time of the reaction with an alkali hydroxide, and the total yield of the anion-radicals does not exceed 10%. Inhibitors (oxygen, potassium ferricyanide) prevent formation of anion-radicals, and the yield of 2-hydroxyanthraquinone even increases somewhat. In this case, the anion-radical pathway is not the main one. The same conclusion is made in the case of oxadiazoloanthraquinone. 

It was found that the intercalation of Cgo fullerene by an alkali metal in stoichiometric ratio (1 1) gives rise to the formation of anion-radical salts, namely, KC50, RbCgg, and CsCgo (Bommeli et al. 1995, Btouet et al. 1996). On slow cooling of the intercalation products, [2 + 2] cycloaddition of the fullerene species that is neighboring a crystal lattice occurs. Linear chain fullerenic polymers are formed. These polymers are stable in air, insoluble in THF, and possess metallic conductivity. They depolymerize only on heating above 320°C. 

In the second approach, M-POMs containing protons as counter ions were used to fulfill electrostatic binding of M-POM to the support in one stage via the formation of anion-cation pairs (Eqs. 3 and 4) ... 

TELLURIUM-MEDIATED FORMATION OF ANIONIC SPECIES AND THEIR REACTIONS WITH ELECTROPHILES... 

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