Ammonium theory

As the number of known coordination compounds increased, theories to explain their constitution were devised.35 Thomas Graham (1805-1869) is credited with originating the first theory of metal ammines, the so-called ammonium theory, in which metal ammines are considered as substituted ammonium compounds. Graham attempted to explain the constitution of compounds such as diamminecopper(II) chloride by the formula (1). 

The next major theory of metal ammines was proposed by Carl Ernst Claus (1796—1864). In 1854, Claus rejected the ammonium theory and suggested a return to Berzelius view of complexes as conjugated compounds. He compared the platinum ammines not with ammonium salts nor with ammonium hydroxide but with metal oxides. He designated the coordinated ammonia molecule as passive, in contrast to the active, alkaline state in the ammonium salts, where it can easily be detected and replaced by other bases . 

The ammonium theory.—In the ammonium theory of H. Davy, A. M. Ampere, and J. J. Berzelius, it was assumed. that the ammonium compounds contain a metallic radicle, NH4 (4.31,38), which may replace potassium, sodium, etc., in different salts. When ammonia unites with hydrogen chloride, the NH4-radicle is formed which unites with chlorine to form ammonium chloride in the same way that potassium united with chlorine forms potassium chloride. The ammonium theory thus corresponds with the ethyl theory of J. J. Berzelius, and J. von Liebig. The nitrogen is assumed to be quinquevalent, and this is in harmony with the work of V. Meyer and M. T. Lecco, A. Ladenburg, and W. Lossen on the quaternary ammonium baseb, and with the isomorphism of the ammonium and the potassium salts. 

H. E. Armstrong emphasized the inadequacy of the ammonium theory to account for the extraordinary stability of tetramethylammonium iodide, (CH3)4NI, towards the strongest caustic alkali, and showed that the halogen compound behaves more like an alkyl iodide than ammonium iodide. Hence, it was inferred that the halogen is not simply associated with the nitrogen, but is rather retained and protected or masked by combination with a hydrocarbon radicle. The idea can be illustrated graphically ... 

The isomeric optically active substituted ammonium salts which have been reported by organic chemists are not readily explained by an ammonium theory such as has been wrongly assumed to have been established by the experiments of V. Meyer and M. T. Lecco—vide supra. J. C. Cain argued from the above hypothesis of the constitution of the ammonium compounds that the optical activity is the result of a similar spatial configuration as that assumed for the carbon compounds where the quadrivalent nucleus, say NCI", instead of quadrivalent carbon, is at the centre of a tetrahedron so that... 

In 1883, Jorgensen reported that tertiary amines form compounds analogous to metal - ammines. Because tertiary amines contain no replaceable hydrogen, Jorgensen s discovery eliminated Graham s ammonium theory (Section 3.1) from serious consideration, leaving the chain theory and Kekule s concept of molecular compounds in the running. In Werner s words, Kekule s dichotomy merely substituted a beautiful word for a confused concept . Therefore, for almost a quarter of a century, until displaced by Werner s coordination theory, the chain theory became the most popular and satisfactory explanation of metal-ammines. 

The ammonium theory.—Although the radical ammonium, NH, has probably never been isolated, its existence in the ammoniacal comisounds is almost universally admitted. The ammonium hypothesis is based chiefly upon the following facts (1) the close resemblance of the ainmoniacaJ salts to those of K and Na (2) when ammonia gas and an acid gas come together, they unite, without liberation of hydrogen to form an ammoni-acal salt (3) the diatomic aiihydrids unite directly with dry ammonia with formation of the ammonium salt of an amido acid ... 

The above is a sketch of the ammonium theory of Berzelius, which is beautifully consistent, if we once admit the existence of ammonium rendered, as it is, so probable by the phenomena of the amalgam, and by the isomorphism of the compounds of potash and those of ammonia + 1 eq. water. This theory is" pretty generally adopted by chemists. 

Graham s ammonium theory, 4 Gravimetry, 524-535 Group overlap integrals angular overlap model, 226 Grunwald-Winstein analysis, 504... 

DanielP at first regarded the ammonium theory as an unnecessary complication [which] tends to perplex the minds of students the formation of ammonium amalgam is due to the force of adhesion, by which the elasticity of the hydrogen and ammoniacal gases is restrained by the action of the mercury but later the view is not wanting in strong analogies for its support . 

The suggestion that alcohol, ether, and some esters contain a radical C2H6 (C = 12) was first made by Kane. Starting from the ammonium theory, he took the radical (4C + 4H) + H (C = 6), which he called ethereum as a constituent of several compounds, such as ether or oxide of ethereum (0 = 8) (4C + 4H) + H + 0, alcohol or hydrate of oxide of ethereum (4C + 4H) + H... 

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