Ammonia the anion

SnBr2 in liquid ammonia. The anionic trigonal pyramidal [Sn(NH2)3] units are linked via interactions with the K+ cations into a strongly distorted hexagonally close-packed array (K-N = 2.907(7) and 2.949(8) A, and Sn is 2.154(7) A). 

XVI), most of the aforementioned change does not appear to be caused by an electron density increase at C-5 but by the change to a dihydropyrimidine structure. This is conceivable if the adduct is not a free anion but is strongly associated with lithium. Further information about the structure of adduct 96 comes from a comparison between the anionic adduct 30 with the neutral adduct 33, formed from pyrimidine and 1-methylpyrimidinium cation, respectively, by reaction with NH2". Here the C-5 position of the anionic adduct is found to be 10.2 ppm upheld with respect to the neutral adduct. If it is assumed that in ammonia the anionic adduct is not associated with the positive counterion, the aforementioned phenyllithium adduct is more likely to possess a slightly delocalized electronic structure (104) resembling that of a dihydropyrimidine. This fact is not surprising, also in view of the low polarity of the solvent. 

Bases behave similarly. Although sodium hydroxide is a strong base in water, it is less ionised in anhydrous alcohol than sodium ethoxide, CgHgONa, the anion of which, CgHgO", also appears in solutions of amines in ethyl alcohol. In hquid ammonia, the anion present is NH ". These liquids exemplify solvents in which the anion is not hydroxide. 

The basis of the CBD method is the slow release of anions (sulfide or selenides) with free metal ions (Cd +, Ztf+, or Pb +) into a solution such that their concentration just exceeds the solubility product of semiconductor. In the bath, a low concentration of the cations is maintained by their complexation with ligands such as TEOA and/or ammonia. The anions are formed by hydrolysis of thiourea, in the case of sulfide, or hydrolysis of selenosulfate or selenourea, in the case of selenides. The material is precipitated due to a super-saturation condition when the concentration of sulfide/selenide anions exceeds the solubility product of CdS/Se. 

The synthesis of N,N-disubstituted-a-arylacetamides can be achieved by reaction of haloarenes with carbanions from N,N-disubstituted amides in liquid ammonia under light initiation. The potassium salt of N-acetylpiperidine does not react, probably due to its low solubility in liquid ammonia. The anions derived from acetamide and N-methyl acetamide are also unreactive. ... 

Silver chloride is readily soluble in ammonia, the bromide less readily and the iodide only slightly, forming the complex cation [Ag(NH3)2]. These halides also dissolve in potassium cyanide, forming the linear complex anion [AglCN) ] and in sodium thiosulphate forming another complex anion, [Ag(S203)2] ... 

The formation of the above anions ("enolate type) depend on equilibria between the carbon compounds, the base, and the solvent. To ensure a substantial concentration of the anionic synthons in solution the pA" of both the conjugated acid of the base and of the solvent must be higher than the pAT -value of the carbon compound. Alkali hydroxides in water (p/T, 16), alkoxides in the corresponding alcohols (pAT, 20), sodium amide in liquid ammonia (pATj 35), dimsyl sodium in dimethyl sulfoxide (pAT, = 35), sodium hydride, lithium amides, or lithium alkyls in ether or hydrocarbon solvents (pAT, > 40) are common combinations used in synthesis. Sometimes the bases (e.g. methoxides, amides, lithium alkyls) react as nucleophiles, in other words they do not abstract a proton, but their anion undergoes addition and substitution reactions with the carbon compound. If such is the case, sterically hindered bases are employed. A few examples are given below (H.O. House, 1972 I. Kuwajima, 1976). 

Step 2 The anion radical is a strong base and abstracts a proton from ammonia ... 

In 1945, cationic urea resins were introduced and quickly supplanted the anionic resins, since they could be used with any type of pulp (62). Although they have now become commodities, their use in the industry has been steadily declining as the shift towards neutral and alkaline papermaking continues. They are commonly made by the reaction of urea and formaldehyde with one or more polyethylene—polyamines. The stmcture of these resins is very compHcated and has not been deterrnined. Ammonia is evolved during the reaction, probably according to the following ... 

Methylpyrazine reacts with sodamide in liquid ammonia to generate the anion, which may be alkylated to give higher alkylpyrazines (Scheme 10) (61JOC3379). The alkylpyrazines have found extensive use as fiavouring and aroma agents (see Section 2.14.4). Condensation reactions with esters, aldehydes and ketones are common, e.g. methyl benzoate yields phenacylpyrazine in 95% yield, and reactions of this type are summarized in Scheme 11. 

Hydrolysis of the trifluoromethyl group of 2 tnfluoiomethylimidazoles is promoted by the formation of the anion, which readily eliminates fluoride. The resultant ditluorodiazafulvene then easily adds water The remaining steps in the hydrolysis ate predictable When aqueous ammonia is used, 2-cyanoimidazoles result [40] (equation 4])... 

Step 2 The anion radical is a strong base and abstracts a proton from ammonia. RC=CR T H-tNH2 -------- RC=CHR -f rNH2... 

The procedure involved in the determination of these anions is virtually that discussed in Section 10.58 for the indirect determination of silver. The anion to be determined is precipitated as the silver salt the precipitate is collected and dissolved in a solution of potassium tetracyanonickelate(II) in the presence of an ammonia/ammonium chloride buffer. Nickel ions are liberated and titrated with standard EDTA solution using murexide as indicator ... 

Ammonium salts of the zeolites differ from most of the compounds containing this cation discussed above, in that the anion is a stable network of A104 and Si04 tetrahedra with acid groups situated within the regular channels and pore structure. The removal of ammonia (and water) from such structures has been of interest owing to the catalytic activity of the decomposition product. It is believed [1006] that the first step in deammination is proton transfer (as in the decomposition of many other ammonium salts) from NH4 to the (Al, Si)04 network with —OH production. This reaction is 90% complete by 673 K [1007] and water is lost by condensation of the —OH groups (773—1173 K). The rate of ammonia evolution and the nature of the residual product depend to some extent on reactant disposition [1006,1008]. 

The introduction of conjugate acid-base pairs completes our inventory of acids and bases, hi addition to strong bases, ammonia, and amines, the anions of weak acids act as bases. 

Table 1.8 Consecutive stability constants, expressed as logXMX., of complexes of ammonia (A), ethylene diamine (B), diethylenetriamine (C) and the anion of ethylenediaminetetraacetic acid (D4 ) at 20°C and 0.1 mKN03 as indifferent electrolyte. (According to J. Bjerrum and G.

Complexation is a phenomenon that involves a coordinate bond between a central atom (the metal) and a ligand (the anions). In a coordinate bond, the electron pair is shared between the metal and the ligand. A complex containing one coordinate bond is referred to as a monodentate complex. Multiple coordinate bonds are characteristic of polydentate complexes. Polydentate complexes are also referred to as chelates. An example of a monodentate-forming ligand is ammonia. Examples of chelates are oxylates (bidentates) and EDTA (hexadentates). 

Research has shown that when polychlorpinen, ammonium nitrate, and superphosphate are present together in the soil, phosgene, carbon monoxide, nitric oxide, hydrochloric acid, ammonia, hydrocyanic anions, ozone, hydrogen fluoride and phosphide, etc. could appear in the air over the beet fields. Photooxidants could also appear. Airborne toxic compounds over this crop were noted in areas after precipitation with little wind, and with an air temperature of over 2CP . The combined and complex activity of pesticides and other chemical compounds led people who manually sowed beets to develop symptoms of poisoning. [21]... 

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