Ammonium ions, solvation

The ammonia molecules occupy trigonal prismatic sites between the dichalcogen layers and NMR measurements show that they are oriented with the threefold axis parallel to the dichalcogenide layers, indicating only weak Lone Pair interactions with the layers. Careful study of the reaction stoichiometry, prompted by this observation, led to the conclusion that ammonia oxidation was involved and that the overall mechanism of reaction conld be summarized by equation (11). The reaction product has x in the range 0.1 -0.3 and contains ammonium ions solvated by nentral ammonia molecules. 

Acids can also exist in non-aqueous solvents. Since ammonia can also solvate a proton to give the ammonium ion. substances... 

The model dealt with here is greatly oversimplified, and is only of qualitative value. It treats solvation on the ammonium ions in terms of a single layer (or shell) of solvent, and ignores solvation of neutral ammonia and trimethylamine. 

The previous calculation assumed that the solvation energy of ammonium was equal the solvation energy of a single water molecule times the number of water binding sites. Is this a valid assumption Compare the electrostatic potential maps of ammonium ion and ammonium ion+water. For which are the exposed hydrogens more acidic Did the calculation underestimate or overestimate the difference in solvation energies ... 

An enormous variety of solvates associated with many different kinds of compounds is reported in the literature. In most cases this aspect of the structure deserved little attention as it had no effect on other properties of the compound under investigation. Suitable examples include a dihydrate of a diphosphabieyclo[3.3.1]nonane derivative 29), benzene and chloroform solvates of crown ether complexes with alkyl-ammonium ions 30 54>, and acetonitrile (Fig. 4) and toluene (Fig. 5) solvates of organo-metallic derivatives of cyclotetraphosphazene 31. In most of these structures the solvent entities are rather loosely held in the lattice (as is reflected in relatively high thermal parameters of the corresponding atoms), and are classified as solvent of crystallization or a space filler 31a). However, if the geometric definition set at the outset is used to describe clathrates as crystalline solids in which guest molecules... 

However, it seems that the magnitude of the repulsive force do not increase significantly as the pressure increases so that eventually, it becomes subdued by the continuous increase in the solvating power causing the overall extraction efficiency to increase once again after 225 bar. After 225 bar, we believe that the efficiency will increase continuously. This is substantiated by an earlier work of Lai [15] where the effect of pressure on the extraction efficiency of the quaternary ammonium ion from the MCM-41 matrix has been studied. In that work, the maximum pressure studied is 350 bar and it was found that the efficiency increases as the pressure increases in the range of 225-350 bar. 

Table 3.14 Free Energies of Ionization and Solvation of Amines and Ammonium Ions...

While the reaction of the solvated electron with hydrogen ions is near the diffusion-controlled limit in aqueous and alcoholic systems (24), the reaction with hydrogen chloride in our system, which presumably gives ethylenediammonium ions, is much slower with k = 1.7 X 106 M l sec."1 Interestingly, the reaction with ammonium ions is at least an order of magnitude faster than this, indicating that appreciable proton transfer from ammonium ion to ethylenediamine does not occur. 

The differences in the basicity order in the gas phase and aqueous solutions are the result of solvation effects. Amines in water solution exist as ammonium ions. 

Solvation is stronger for the alkyl ammonium ion formed from a primary amine than for the alkyl ammonium ion formed from a tertiary amine. This is due to the fact that the former ion has three N-H hydrogens available for H-bonding, compared with only one such N-H hydrogen the latter. 

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