Functionalized Anions

The reaction between a trinuclear metal carbonyl cluster and trimetbyl amine borane has been investigated (41) and here the cluster anion functions as a Lewis base toward the boron atom, forming a B—O covalent bond (see Carbonyls). Molecular orbital calculations, supported by stmctural characterization, show that coordination of the amine borane causes small changes in the trinuclear framework. 

The compounds obtained in solid state have the general formula [MefSCNf JR., (R-cations of cyanine dyes) and could be embedded into polyvinylchloride matrix. Using the matrix as work element of electrodes shows the anionic function concerning the anionic thiocyanate complexes of Pd, Hg, Zn and the response to sepai ately present thiocyanate and metallic ions is not exhibited. 

The factors that determine whether syn or anti elimination predominates are still subject to investigation. One factor that is believed to be important is whether the base is free or present in an ion pair. The evidence is that an ion pair promotes syn elimination of anionic leaving groups. This effect can be explained by proposing a transition state in which the anion functions as a base and the cation assists in the departure of the leaving group. 

Due to the fact that the primary structure of the Ultrahydrogel packing is a hydroxylated methacrylate, the interaction of many polar polymers with the packing is minimized easily. The presence of small amounts of anionic functions on the surface of the polymer usually requires the addition of salt to the mobile phase. A common mobile phase for many applications is 0.1 M NaN03. Detailed eluent selection guidelines are given in Table 11.6. 

This reaction is driven to the right in tissues by the high COg concentration the equilibrium shifts the other way in the lungs where [COg] is low. Thus, car-bamylation of the N-termini converts them to anionic functions, which then form salt links with the cationic side chains of Arg al41 that stabilize the deoxy or T state of hemoglobin. 

The anionic portions of the soil solution play a role of equal importance to the cations. The anions function in the manner outlined for cations in conductivity and concentration-cell action, and have an additional action if they react with the metal cation and form insoluble salts. Thus, if the metal is lead and the predominant anion is sulphate, a layer of insoluble lead sulphate may precipitate on the metal surface and form an effective barrier against further loss of metal. 

Recently it has been shown that anionic functionalization techniques can be applied to the synthesis of macromonomers — macromolecular monomers — i.e. linear polymers fitted at chain end with a polymerizable unsaturation, most commonly styrene or methacrylic ester 69 71). These species in turn provide easy access to graft copolymers upon radical copolymerization with vinylic or acrylic monomers. 

Anionic domino processes are the most often encountered domino reactions in the chemical literature. The well-known Robinson annulation, double Michael reaction, Pictet-Spengler cyclization, reductive amination, etc., all fall into this category. The primary step in this process is the attack of either an anion (e. g., a carban-ion, an enolate, or an alkoxide) or a pseudo anion as an uncharged nucleophile (e. g., an amine, or an alcohol) onto an electrophilic center. A bond formation takes place with the creation of a new real or pseudo-anionic functionality, which can undergo further transformations. The sequence can then be terminated either by the addition of a proton or by the elimination of an X group. 

Salts with oxometallate anions function as oxidants, those with oxygen present as peroxo groups being naturally the more powerful, and separately grouped under See also peroxoacid salts... 

The first chemical transformations carried out with Cjq were reductions. After the pronounced electrophilicity of the fullerenes was recognized, electron transfer reactions with electropositive metals, organometallic compounds, strong organic donor molecules as well as electrochemical and photochemical reductions have been used to prepare fulleride salts respectively fulleride anions. Functionalized fulleride anions and salts have been mostly prepared by reactions with carbanions or by removing the proton from hydrofullerenes. Some of these systems, either functionalized or derived from pristine Cjq, exhibit extraordinary solid-state properties such as superconductivity and molecular ferromagnetism. Fullerides are promising candidates for nonlinear optical materials and may be used for enhanced photoluminescence material. 

Interesting variations of these reactions are observed when the a-silylamine donor funtion is tethered to an enone. For example, the intramolecular ET reaction of 143 results in two divergent cyclizations. Methanol assists the cleavage of the C—Si bond the resulting biradical anion 146 couples protonation and tautomer-ization then leads to 147. In acetonitrile, on the other hand, transfer of an a proton to the enone radical anion function forms biradical 144 coupling and tautomer-ization then generates 145. " ... 

Ion bridging is a specific type of Coulombic interaction involving the simultaneous binding of polyvalent cations (e.g., Ca, Fe, Cu ) to two different anionic functional groups on biopolymer molecules. This type of ionic interaction is commonly involved in associative self-assembly of biopolymers. As a consequence it is also an important contributory factor in the flocculation (via bridging or depletion) of colloidal particles or emulsion droplets in aqueous media containing adsorbed or non-adsorbed biopolymers (Dickinson and McClements, 1995). 

Although many complexes are known in which the trichlorostannate(II) anion functions as a donor to transition metals, very few to main group Lewis acids have been described and no strucural data are available. However, the complexes B- SnX2- -BF3 (X = Cl, Br, I B = NMe3, bipy, TMEDA and DMSO), in which the tin(II) halide functions simultaneously as both a Lewis acid and a Lewis base, have been reported.1 ... 

Like other aieas of spectioscopy, visible spectrometry has a wide range of applications. Included are most of the elements, many anions, functional groups, and innumerable compounds. 

The majority of useful lyase families utilize anionically functionalized substrates such as pyruvate or dihydroxyacetone phosphate which remain unaltered during catalysis. The charged group thereby introduced into the products (phosphate, carboxylate) not only constitutes a handle for binding of the substrates by the enzymes but also can facilitate the preparative isolation from... 

This large and commonly used class of salts covers a wide range of oxidising potential. Among the more powerful oxidants are those grouped for which separate entries emphasise the individual features. Some less highly oxidised anions function as reducants which also have a separate entry. Individually indexed entries are ... 

The amide anion functions as a Bronsted-Lowry base. It accepts a proton from a terminal acetylene, which functions as a Bronsted-Lowry acid. 

Gurkan BE, de la Fuente JC, Mindrup EM et al (2010) Equimolar C02 absorption by anion-functionalized ionic liquids. J Am Chem Soc 132(7) 2116-2117... 

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