Radicals ammonium

For uniformity with the stmctures given in the Colourindex the ammonium radical (9) is used for the amino-substituted xanthenes and the keto form for the hydroxy derivatives. The xanthene dyes may be classified into two main groups diphenylmethane derivatives, called pyronines, and triphenylmethane derivatives (eg, (4)), which are mainly phthaleins made from phthaUc anhydride condensations. A third much smaller group of rosamines (9-phenylxanthenes) is prepared from substituted ben2aldehydes. The phthaleins may be further subdivided into the following fluoresceins (hydroxy-substituted) rhodamines (amino-substituted), eg, (6) and mixed hydroxy/amino-substituted. 

Ammonium-ferrisulfat, n. ammonium iron(III). sulfate, ferric ammonium sulfate, -ferro-sulfat, n. ammonium iron(II) sulfate, ferrous ammonium sulfate, -jodat, n. ammonium iodate. -jodid, n. ammonium iodide, -platinchlorid, n. ammonium platinichloride (chloroplatinate). -rest, m. ammonium radical. rhodanid, -rhodantir, n. ammonium thiocyanate, -salpeter, m. ammonium nitrate, -salz, n. ammonium s t. -selfe,/. ammonia soap, -sulfhydrat, n. ammonium hydrosulfide, -sulfocyanid, n. ammonium thiocyanate, -verbindung,/. ammonium compound, -zinn-chlorid, n. ammonium chlorostannate, pink salt. 

Ammonium, Metal(Metal Ammonium). Solutions of mercury arid the alkali metals in liq ammonia were first prepd and studied by Weyl (Ref 1). According to his views, the metals are joined to the nitrogen of ammonia, forming substituted ammonium radicals. Many investigators later studied the solns of metals in liq ammonia and while a few of the investigators were in favor of Weyl s theory(Joannis in 1892, Moissan in 1898 and Benoit in 1923), others were against it(Seeley in 1871, Ruff and Geisel in 1906, Kraus in 1908, Biltz in 1920 etc)... 

In an aqueous solution containing ammonium perdisulphate only, the ammonium radical is gradually converted into nitric acid, this reaction explaining why the decomposition of ammonium perdisulphate diverges somewhat from the simple unimolecular course 4 (p. 183). Hydrazine in aqueous solution, prepared by the addition of an alkali to hydrazine sulphate, is similarly oxidised to nitrogen by perdisulphates 5... 

Fig. 5.2 (a) Polyacrylic acid (b) poly-methacrylic acid. Note that in both PA A and PMAA, the acid s hydrogen component can be replaced by Na, other monovalent cation, or ammonium radical... 

The chloro substituent is electron withdrawing inductively and electron donating in resonance. This explains the observation that the mobility of 3,9-dichloro substituted indolo[3,2-b]carbazole 5d is an order of magnitude lower than that of its regioisomeric 2,8-dichloro analog 5c. The two chloro substituents of 5d, which are positioned meta to 5,11-ammonium radical cation sites, exert inductive but not resonance effects. 

When ammonium hydroxide dissociates electrolytically it yields the ion NHV". The group of atoms NH4, which is often spoken of as the ammonium radical, resembles in many respects the atom of sodium or potassium. Like these, it can form a monovalent positive ion, or it can form compounds with acid radicals, for example, NH4CI, (NID2SO4 but unlike sodium and potassium, it cannot exist in the uncombined state. 

Characteristic of this process is the low concentration of chiral cation necessary to induce optical activity (10% of the substrate concentration is sufficient) and that the chiral salt is recovered mostly unchanged (except for no. 3). Quaternary ammonium ions work as well as substituted ammonium ions, thereby making less probable the mechanism first suggested (Gourley et al., 1967, 1970), namely, hydrogen atom transfer from an ammonium radical R3NH to the substrate. Today it seems reasonably well established that adsorption of the chiral cation, possibly as a complex with an intermediate is connected with the asymmetric induction observed (Horner et al., 1972 Kariv et al., 1973a). 

Ammonium ion is reduced at about -1.7 V and creates amalgam of ammonium radical ... 

The lifetimes of hypervalent radicals have been found to depend rather dramatically on isotope substitution. For example, dimethyloxonium, (CH3)2OH, dissociates completely on a 1 -ps time scale when formed by collisional reduction of the stable cation (CH3)2OH+. By contrast, (CH3)2OD furnishes an abundant survivor ion in the +NR+ mass spectrum that is evidence that the deuterated hypervalent radical is metastable [178,179]. From the time scale of the NR measurements and the survivor ion relative intensities one can estimate that (CH3)2OH dissociates >5 times faster than (CH3)2OD. Similar isotope effects have been observed for CH3OH [180], C2H5OH [181], and hypervalent ammonium radicals, e.g., CH3NH [182], (CH3)2NH [60], (CH3)3NH [183], and [pyrrolidinium] [184], which are metastable only as deuterated species. 

Preparation.—Being very sensitive to rise of temperature, the isolation of the ammonium radical by the electrolysis of solutions of ammonium salts in liquid ammonia is probably precluded by the thermal effect of the current. Its formation by the interaction of well-cooled ammonium chloride and a solution of potassium in liquid ammonia at —70° C. is indicated by a deficit of as much as 65 per cent, in the volume of the hydrogen evolved.1... 

A peroxide, probably Ag203, is stated to be produced by anodic oxidation of silver in acid solution.4 When solutions of sodium or potassium persulphate react with silver or silver nitrate, a peroxide with a higher percentage of oxygen than Ag2Oa is produced, the process being attended by catalytic decomposition of the persulphate with formation of the acid sulphate. Ammonium persulphate does not yield a peroxide, but the ammonium radical becomes oxidized to nitric acid.6... 

As might be expected not all attempts to prepare and trap a given radical have been successful. Of particular interest amongst the failures are the ammonium radical, NH4, the phenylperoxy and the alkoxy radicals. 

Theoretical calculations (Bernstein, 1963 Bishop, 1964) have predicted that the ammonium radical, NH4, may have a stability of a few kilocalories and so might be stable at 77°K. We have attempted to produce the radical by the reaction of an alkali metal with ammonium chloride in a variety of matrices but have not been successful. 

A reagent wiiich may operate by hydrogen atom abstraction fr n the alkane by the intormediaie alkyl-ammonium radical cation is iron(II)/R2NCl/CF3C02H, which affords secondary chlorides in good yield from R-alkanes without overoxidation. 

Na+OH, Na+NH2, Na+CH3 or the covalent compounds CH3F, CH3OH, CH3NH2, and CH3CH3. The ammonium radical NH4-, which is isosteric to the alkali metals, has so far not been isolated. 

A stable triarylaminium salt (2) was isolated by Wieland in 1907 [3]. Neither 1 nor 2 was recognized as a cation radical salt, since this concept had not yet even begun to emerge. It was not until 1926 that Weitz formulated the corresponding perchlorate salt of 2 as a delocalized cation which is also a free ammonium radical [4]. Michaelis then made Weitz s interpretation more certain via electrochemical oxidation studies, and he coined the term cationic free radical , which is the appropriate antecedent of the current term cation radical [5]. Since that time, many other cation radical salts have been prepared, but the salts S " and 4 have an especially important role in the electron transfer chemistry of cation radicals [6, 7],... 

Tertiary ammonium radicals are also acidic so, if (x-CH protons are present in the amine, deprotonation of these intermediate products stabilizes the a-amino radicals... 

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