With Anions

Li J and Abruna FI D 1997 Coadsorption of sulphate/bisulphate anions with Fig cations during Fig underpotential deposition on Au (111) An In situ x-ray diffraction study J. Phys. Chem. B 101 244-52... 

For the most part it is true to say that the chemistry of the alkali and alkaline earth metal compounds is not that of the metal ion but rather that of the anion with which the ion is associated. Where appropriate, therefore, the chemistry of these compounds will be discussed in other sections, for example nitrates with Group V compounds, sulphates with Group VI compounds, and only a few compounds will be discussed here. 

The mechanism of the reaction may involve the formation of an anion by the base B, followed by the shift of hydrogen on the hydrazone anion with simultaneous loss of nitrogen to yield a carbanion ... 

Reaction of the cnrbaiilon (acetone anion) with the carbonyl carbon of ethyl acetate, accompanied by the release of an ethoxide ion, to form acetyl-acetone ... 

So far in this section we have combined enolate anions with other carbonyl compounds by direct attack at the carbonyl group. We can expand the scope of this reaction by using a,p-unsaturated carbonyl compounds as the electrophiles. This is the Michael reaction. Remind yourself of tliis by writing out the mechanism of a Michael reaction such as ... 

In contrast to alkylations with most of the alkyl halides, the reactions of anions with ethylene oxide in organic solvents such as diethyl ether and THE... 

The reaction of cumulenic anions with electrophiles in principle may give two products ... 

The allyl-substituted cyclopentadiene 122 was prepared by the reaction of cyclopentadiene anion with allylic acetates[83], Allyl chloride reacts with carbon nucleophiles without Pd catalyst, but sometimes Pd catalyst accelerates the reaction of allylic chlorides and gives higher selectivity. As an example, allylation of the anion of 6,6-dimethylfulvene 123 with allyl chloride proceeded regioselectively at the methyl group, yielding 124[84]. The uncatalyzed reaction was not selective. 

Salts composed of an anion, RO—, and a cation, usually a metal, can be named by citing first the cation and then the RO anion (with its ending changed to -yl oxide), e.g., sodium benzyl oxide for CgH5CH20Na. However, when the radical has an abbreviated name, such as methoxy, the ending -oxy is changed to -oxide. For example, CHjONa is named sodium methoxide (not sodium methylate). 

If the coordination entity is negatively charged, the cations paired with the complex anion (with -ate ending) are listed first. If the entity is positively charged, the anions paired with the complex cation are listed immediately afterward. 

Dowex 1-X8 1.2 0.75 Strongly basic anion exchanger with S-DVB matrix for separation of inorganic and organic anions with molecular weight exclusion < 1000. 100-200 mesh is standard for analytical separations. 

Ion-Exchange Equilibrium. Retention differences among cations with an anion exchanger, or among anions with a cation exchanger, are governed by the physical properties of the solvated ions. The stationary phase will show these preferences ... 

C and melts at 173°C. It is iasoluble ia water but dissolves ia alcohols, ether, and benzene. Ferrocene can be prepared by numerous methods, including the reaction of cyclopentadienyl anion, with anhydrous FeCl2. Its extensive reaction chemistry is notable for the aromaticity of the... 

Examples include luminescence from anthracene crystals subjected to alternating electric current (159), luminescence from electron recombination with the carbazole free radical produced by photolysis of potassium carba2ole in a fro2en glass matrix (160), reactions of free radicals with solvated electrons (155), and reduction of mtheiiium(III)tris(bipyridyl) with the hydrated electron (161). Other examples include the oxidation of aromatic radical anions with such oxidants as chlorine or ben2oyl peroxide (162,163), and the reduction of 9,10-dichloro-9,10-diphenyl-9,10-dihydroanthracene with the 9,10-diphenylanthracene radical anion (162,164). Many other examples of electron-transfer chemiluminescence have been reported (156,165). 

Under optimum conditions electron transfer can produce excited states efficiently. Triplet fluoranthrene was reported to be formed in nearly quantitative yield from reaction of fluoranthrene radical anion with the 10-phenylphenothia2ine radical cation (171), and an 80% triplet yield was indicated for electrochemiluminescence of fluoranthrene by measuring triplet sensiti2ed isomeri2ation of trans- to i j -stilbene (172). 

According to this mechanism, the reaction rate is proportional to the concentration of hydronium ion and is independent of the associated anion, ie, rate = / [CH3Hg][H3 0 ]. However, the acid anion may play a marked role in hydration rate, eg, phosphomolybdate and phosphotungstate anions exhibit hydration rates two or three times that of sulfate or phosphate (78). Association of the polyacid anion with the propyl carbonium ion is suggested. Protonation of propylene occurs more readily than that of ethylene as a result of the formation of a more stable secondary carbonium ion. Thus higher conversions are achieved in propylene hydration. 

Other expansion reactions between diborane and borane anions with a B—B edge bond have been reported (79), for example... 

The crown ethers and cryptates are able to complex the alkaU metals very strongly (38). AppHcations of these agents depend on the appreciable solubihty of the chelates in a wide range of solvents and the increase in activity of the co-anion in nonaqueous systems. For example, potassium hydroxide or permanganate can be solubiHzed in benzene [71 -43-2] hy dicyclohexano-[18]-crown-6 [16069-36-6]. In nonpolar solvents the anions are neither extensively solvated nor strongly paired with the complexed cation, and they behave as naked or bare anions with enhanced activity. Small amounts of the macrocycHc compounds can serve as phase-transfer agents, and they may be more effective than tetrabutylammonium ion for the purpose. The cost of these macrocycHc agents limits industrial use. 

Mechanisms of Coupling. Because the active coupling species is the ioni2ed coupler (35,52), the rate of the coupling reaction and hence its abihty to compete for oxidi2ed developer is dependent on the pH of the process, the piC or acidity of the coupler or less frequentiy the rate of coupler ioni2ation, and the reactivity of the resulting coupler anion with the QDI (40). 

Oxidation of azole anions can give neutral azole radicals which could, in principle, be tt (139) or a- (140) in nature. ESR spectra indicate structure (141 hyperfine splittings in G) for imidazolyl radicals, but both tt- and cr-character have been observed for pyrazolyl radicals. Tetrazolyl radicals (142 4 143) are also well known (79AHC(25)205). Oxidation of 2,4,5-triarylimidazole anions with bromine gives l,l -diimidazolyls (144) which are in equilibrium with the dissociated free radical (145) (70AHQ 12)103). 

The pattern of reactivity is similar to that discussed for the azolinones in Sections 4.02.1.1.4 and 4.02.3.7.1. A difference is the greater nucleophilicity of sulfur, and thus more reaction of the ambident anion with electrophiles occurs at sulfur. 

Reaction of the pyrazole anion with (498 Y = NO2, X = Cl) in DMSO yields the pyrazolyl-pyrazole (500) (81M675). 

O-Alkylation of A-unsubstituted /3-lactams to give the corresponding 2-alkoxy-l- etines can be achieved by reaction of the azetidin-2-ones with hard electrophiles (trialkyloxonium tetrafluoroborates) followed by treatment with base (cf. Section 5.09.4.3.1) (67JHC619, 69LA(725)124). In contrast, reaction of the A-unsubstituted azetidin-2-ones (73) or their derived anions with a variety of softer electrophiles results in A-substitution, and some representative reactions are illustrated in Scheme 7. 

In a like manner the 6/3-isocyano group can be utilized to activate the C(6) proton (79JCS(P1)2455), an example of which is shown in Scheme 43. It was also possible to introduce the 6a-methylthio substituent by reacting the intermediate anion with methyl methoxycarbonyl disulfide The 6a-methylthio group could subsequently be converted to the 6a-methoxy group by treatment with CI2 and MeOH. 

REDUCTIVE RING CONTRACTION OF , DISUBSTITUTED SULFOLANE ANIONS WITH LITHIUM ALUMINUM HYDRIDE... 

Condensation of thiophenoxide anions with various fluonnated polychloro- or polybromoethanes gives fluoroalkyl phenyl sulfides [57, 52, 55], These formal substitutions involve fluonnated olefins as intermediates [52, 55], In the case of perhalogenated ethanes, the mechanism shows a similarity with that of dihalo-genodifluoroinethane [52] (equations 46 and 47)... 

Perfluoroalkylation of substituted benzenes and heterocyclic substrates has been accomplished through thermolysis of perfluoroalkyl iodides in the presence of the appropriate aromatic compound Isomeric mixtures are often obtained W-Methylpyrrole [143] and furan [148] yield only the a-substituted products (equation 128) Imidazoles are perfluoroalkylated under LTV irradiation [149] (equation 129). 4-Perfluoroalkylimidazoles are obtained regioselectively by SET reactions of an imidazole anion with fluoroalkyl iodides or bromides under mild conditions [150] (equation 130) (for the SET mechanism, see equation 57)... 

Pentamethylcyclopentadienyl substituted boron complexes arc obtamed by the reaction of the pentamethylcyclopentadienyl anion with boron tnfluonde [109] (Table 27) Similarly, the Gngnard reagent prepared from 3,5-bis(tnfluorometh-yl)iodobenzene reacts with sodium tetrafluoroborate to form the phase-transfer eatalyst 2 under anhydrous eonditions [110] (equation 87)... 

Complexes of the sulfenamido anion [RSNR ] with several transition metals [Zr(IV), Ti(IV), Mo(VI), W(Vf), Ni(If), and U(IV)] are known.They are prepared by the reaction of the lithium derivative of the sulfenamido anion with a metal halide complex. A selenium complex W(N Bu)2( BuNSePh)2 has been obtained in a similar... 

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