Solvated electron ammoniated

The alkali metals are soluble in liquid ammonia, and certain amines, to give solutions which are blue when dilute. The solutions ate paramagnetic and conduct electricity, the carrier being the solvated electron. In dilute solutions the metal is dissociated into metal ions and ammoniated electrons. The metal ions are solvated in the same way that they would be in a solution of a metal salt in ammonia, and so comparison can be made with, for example, [Na(NH3)4]+I-, the IR and Raman spectra of which indicate a tetrahedral coodination sphere for the metal.39... 

In the century since its discovery, much has been learned about the physical and chemical properties of the ammoniated electron and of solvated electrons in general. Although research on the structure of reaction products is well advanced, much of the work on chemical reactivity and kinetics is only qualitative in nature. Quite the opposite is true of research on the hydrated electron. Relatively little is known about the structure of products, but by utilizing the spectrum of the hydrated electron, the reaction rate constants of several hundred reactions are now known. This conference has been organized and arranged in order to combine the superior knowledge of the physical properties and chemical reactions of solvated electrons with the extensive research on chemical kinetics of the hydrated electron. 

For example, the one-electron models incorrectly predict (even at a qualitative level) the Knight shifts in and NMR spectra of ammoniated electron, and solvated electrons in amines (Sec. 4.1). The same problem arises in the explanation of magnetic (hyperfine) parameters obtained from ESEEM spectra of trapped (hydrated) electrons in low-temperature alkaline ices. The recent resonance Raman spectra of also appear to be incompatible with the one-... 

A powerful aprotic solvent capable of dissolving alkali and alkaline earth metals is hexamethylphosphoramide. The characteristic blue paramagnetic solution is observed [101]. It had been demonstrated that the ammoniated electron could be produced in the electrolysis of liquid ammonia [102] and recently it has been demonstrated that the solvated electron is produced in the electrolysis of hexeimethylphosphoramide [103, 104]. It is, however, doubtful whether eaq can be produced in this manner [102]. 

Many of the available computations on radicals are strictly applicable only to the gas phase they do not account for any medium effects on the molecules being studied. However, in many cases, medium effects cannot be ignored. The solvated electron, for instance, is all medium effect. The principal frameworks for incorporating the molecular environment into quantum chemistry either place the molecule of interest within a small cluster of substrate molecules and compute the entire cluster quantum mechanically, or describe the central molecule quantum mechanically but add to the Hamiltonian a potential that provides a semiclassical description of the effects of the environment. The 1975 study by Newton (28) of the hydrated and ammoniated electron is the classic example of merging these two frameworks Hartree-Fock wavefunctions were used to describe the solvated electron together with all the electrons of the first solvent shell, while more distant solvent molecules were represented by a dielectric continuum. The intervening quarter century has seen considerable refinement in both quantum chemical techniques and dielectric continuum methods relative to Newton s seminal work, but many of his basic conclusions... 

The solvated, or ammoniated, electron is depicted in a cavity in the structure of hydrogen-bonded liquid ammonia. 

KLEIN - Yes, indeed, we are I My group Massimo Marchi and Michiel Sprik have written a constant-pressure Monte-Carlo program to study the electron-solvent system. To-date, only preliminary results are available they are sufficiently encouraging that we are actively pursuing this avenue of research. It will be necessary to compare and contrast the behaviour of hydrated and ammoniated electrons. Another quantity of interest is S, the entropy change on solvation. We are also attempting to calculate AS for the solvated electron. This story is nearly finished and will be submitted for publication shortly. 

As was mentioned in section 2.3.3, ytterbium metal dissolves in liquid ammonia to yield ammoniated electrons and Yb " ions. This solution was used by White et al. (1978) to perform reductions of various aromatic systems, similar to the Birch reactions which use lithium or sodium as the metal. The addition of benzoic acid or anisole dissolved in a 10 1 mixture of THF-tert-butyl alcohol, to an ytterbium-ammonia solution gives 1,4-dihydrobenzoic acid (56% yield). Triple bonds are cleanly reduced to trans olefins (i.e. PhC CPh traK5-PhCH=CHPh 75%). The C=C double bonds of conjugated ketones are also reduced by this system. Since the reaction medium initially contains both solvated electrons and Yb + ions it is likely that the above reactions are not directly connected with the presence of divalent ytterbium species. 

Although agreement among workers in the field is not complete, it now appears that the predominant species in concentrated solution is the solvated Na2 molecule with the two 3a electrons delocalized over a number of surrounding solvent molecules, but still paired. The blue species is probably an ammoniated electron—that is, the electride ion. ... 

A stabilization of NH5 by solvation was suggested in a study of reactions following electron impact ionization of neat cluster beams of ammonia and of heteroclusters of ammonia-benzene. Peaks in the mass spectrum were assigned to [NH5(NH3)n] adducts, where n>4. Analogous results were obtained with deuterated ammonia [3]. An ab initio SCF MO study on ammoniated NH5 adducts [2] indicated that the species observed in the mass spectrum [3] is possibly ammoniated N2H8 ( = NH4NH4). 

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