Anion transfer

In these cydizations, the reaction can be terminated in other ways than elimination of /3-hydrogen. Typically the reaction ends by an anion capture process[154]. The following anion transfer agents are known H, OAc , CN, S02Ph, CH(C02R)2, NHRj, CO/ROH, and RM [M = Sn(IV), B(lll), Zn(II)]. Trapping with an amine after alkene insertion to give 189 and 190 is an example. A-Acetyl protection is important in this reaction[155]. 

Electrodialysis. Electro dialysis processes transfer ions of dissolved salts across membranes, leaving purified water behind. Ion movement is induced by direct current electrical fields. A negative electrode (cathode) attracts cations, and a positive electrode (anode) attracts anions. Systems are compartmentalized in stacks by alternating cation and anion transfer membranes. Alternating compartments carry concentrated brine and purified permeate. Typically, 40—60% of dissolved ions are removed or rejected. Further improvement in water quaUty is obtained by staging (operation of stacks in series). ED processes do not remove particulate contaminants or weakly ionized contaminants, such as siUca. 

C Cation transfer membrane A Anion transfer membrane... 

When halide ions or anions such as thiocyanate or azide are present, these anions are incorporated into the organic radical generated by decomposition of the peroxide. This anion transfer presumably occurs in the same step as the redox interaction with Cu(II), and such reactions have been called ligand-transfer reactions. " ... 

The use of tetra-alkylphosphonium salts to catalyse heterogeneous reactions involving anion transfer has been described. ... 

A surprising exception has been reported with evidence for a cleavage reaction in the case of divinyl sulphone. In non-aqueous and slightly acidic media, the behaviour of a., ji-unsaturated aromatic sulphones is also complex (see Table 7) since the cleavage and the saturation may compete. Strongly electrophilic double bonds undergo Michael additions in aprotic solvents by slowly protonated anions. Transfer of labile hydrogen may also lead to unactivated bases. It is noteworthy that in numerous cases (Table 6) the saturation is the preferred route. 

Certain negative ions such as Cl , Br, CNS , N03 and SO2 show an adsorption affinity to the mercury surface so in case (a), where the overall potential of the dme is zero, the anions transfer the electrons from the Hg surface towards the inside of the drop, so that the resulting positive charges along the surface will form an electric double layer with the anions adsorbed from the solution. Because according to Coulomb s law similar charges repel one another, a repulsive force results that counteracts the Hg surface tension, so that the apparent crHg value is lowered. 

The naphthalene radical-anion transfers an electron to a monomer such as styrene to form the styryl radical-anion which dimerizes to a dianion... 

Grigg developed several palladium-catalyzed tandem cyclization-anion capture processes, and these include organoboron anion transfer agents [112, 164, 206]. Two examples of this methodology are shown. 

C. M. Starks, Phase-Transfer Catalysis. L Heterogeneous Reactions Involving Anion Transfer by Quaternary Ammonium and Phosphonium Salts , J. Am. Chem. Soc 1971, 93,195-199. 

Starks, C. M. J. Am. Chem. Soc. 93 (1971) 195 Phase transfer catalysis I. Heterogeneous reactions involving anion transfer by quaternary phosphonium salts. 

As shown in Fig. 7-1, the electrode reaction in which a particle of negative charge (electron or anion) transfers finm an electrode to an electrol3de (aqueous solution) is called the cathodic reaction-, and the electrode reaction in which a particle of positive charge (hole or cation) transfers from an electrode to an electrolyte is called the anodic reaction. Further, the electrode at which the cathodic reaction takes place is called the cathode and the electrode at which the anodic reaction takes place is called the anode. 

If the anodic anion transfer (anionic adsorption, Eqn. 9-13a) to form an adsorbed metallic ion complex is the rate-determining step, the Tafel constant, a = 1 - p, win be obtained from Eqn. 9-14. If the anodic transfer of the adsorbed metallic ion complex (desorption of complexes, Eqn. 9-13b) is the rate-determining step, the Tafel constant, a = 2 - p, will be obtained from Eqns. 9-16 and 9-17. Similarly, if the cathodic anion transfer (anionic desorption, Eqn. 9-13a) is determining the rate, the Tafel constant in the cathodic reaction, a = 1 p, will be obtained from Eqns. 9-15 and 9-16 and if the cathodic transfer of a metallic ion complex (adsorption of complexes, Eqn. 9-13b) is determining the rate, the Tafel constant, a-sp, will be obtained from Eqn. 9-18. In this discussion we have assumed Pi = Ps P then, Eqns. 9-19 and 9-20 follow ... 

From neutrality requirement, the anodic current of cation transfer equals the cathodic current of anion transfer. The transfer rate of cations and the transfer... 

About ten years ago a knowledgeable organic chemist offered the opinion that "almost all the things that can be done via phase transfer catalysis has already been done." He was wrong, of course, as one can now look back and see that the great bulk of PTC chemistry now known came after his comment was made. While it may be true that many of the obvious and direct applications of PTC, especially for anion transfer, have been identified, it seems most likely to this author that a vast amount of new applications and more complex catalyst systems based on PTC await discovery and exploitation. 

In the theoretical modeling, the kinetics of anion transfer is assumed to obey the Butler-Volmer equation [29] ... 

Fig. 4.11 Experimental quasireversible maxima corresponding to anion transfers from water to nitrobenzene measured by the oxidation of LBPC. The concentrations of the transferring ion are c = 1 mol/L and c =0.1 mol/L. All other conditions were the same as in the caption of...

The stability of (20e) anion [(cp)Fe(CgHg)] sharply diminishes when this (20e) anion transfers from the salt with (cp)Fe(PMe3)3 into the salt with Na. The sodinm salt is decomposed easily. 

C-H bond oxygen insertion, 1163 configuration retention, 1163 epoxidation, 1144-50 hydroperoxy anion transfer, 382 Steric effects hydrogen dioxide, 96-7 peroxide dihedral angle, 101, 177 Steric strain... 

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