Dipoles ammonia

Similar, very detailed studies were made by Ebert [112] on water adsorbed on alumina with similar conclusions. Water adsorbed on zeolites showed a dielectric constant of only 14-21, indicating greatly reduced mobility of the water dipoles [113]. Similar results were found for ammonia adsorbed in Vycor glass [114]. Klier and Zettlemoyer [114a] have reviewed a number of aspects of the molecular structure and dynamics of water at the surface of an inorganic material. 

Phosphine is a colourless gas at room temperature, boiling point 183K. with an unpleasant odour it is extremely poisonous. Like ammonia, phosphine has an essentially tetrahedral structure with one position occupied by a lone pair of electrons. Phosphorus, however, is a larger atom than nitrogen and the lone pair of electrons on the phosphorus are much less concentrated in space. Thus phosphine has a very much smaller dipole moment than ammonia. Hence phosphine is not associated (like ammonia) in the liquid state (see data in Table 9.2) and it is only sparingly soluble in water. 

H2O2 (hydrogen peroxide) chirality, 80 symmetry elements, 82 NF3 (nitrogen trifluoride) dipole moment, 98, 99 NFl3 (ammonia)... 

Purine, 6-bromo-9-/3-D-(2,3,5-tri-0-acetyl)ribofuranosyl-synthesis, 5, 598 Purine, 6-carboxy-reactions, 5, 549 Purine, 8-carboxy-reactions, 5, 549 Purine, 2-chloro-reactions, 5, 561 synthesis, 5, 597 Purine, 6-chloro-alkylation, 5, 529 glycosylation, 5, 529 oxidation, 5, 539 3-oxides reactions, 5, 554 synthesis, 5, 595 reactions, 5, 561, 595 with ammonia, 5, 562 with fluorides, 5, 563 with trimethylamine, 5, 562 9- -D-ribofuranoside synthesis, 5, 560 synthesis, 5, 597, 598 Purine, 8-chloro-amination, 5, 542 Purine, 6-chloro-8-ethoxy-synthesis, 5, 591 Purine, 6-chloro-9-ethyl-dipole moment, 5, 522 Purine, 6-chloro-2-fluoro-riboside... 

It is clear from Table 1 that, for a few highly polar molecules such as water, the Keesom effect (i.e. freely rotating permanent dipoles) dominates over either the Debye or London effects. However, even for ammonia, dispersion forces account for almost 57% of the van der Waals interactions, compared to approximately 34% arising from dipole-dipole interactions. The contribution arising from dispersion forces increases to over 86% for hydrogen chloride and rapidly goes to over 90% as the polarity of the molecules decrease. Debye forces generally make up less than about 10% of the total van der Waals interaction. 

The Hydrolysis of Salts. As shown in Table 41, the NH,i molecule has a dipole moment almost as large as that of the H20 molecule. When ammonia has been dissolved in water the electrostatic interaction of an NH3 dipole with an adjacent solvent dipole is of the same order of magnitude as the interaction between two adjacent H20 dipoles. At the same time, when ammonia has been dissolved in water, the solution has a feeble electrical conductivity, due to the fact that a certain... 

In contrast with water, methanol, ammonia, and other substances in Table 2.1, carbon dioxide, methane, ethane, and benzene have zero dipole moments. Because of the symmetrical structures of these molecules, the individual bond polarities and lone-pair contributions exactly cancel. 

SOLUTION The N2 and C02 molecules are nonpolar (Chapter 7), so only dispersion forces are present. Both CHC13 and NH3 are polar molecules. Chloroform contains dipole forces as well as dispersion forces. Ammonia contains hydrogen bonds as well as dispersion forces. 

The ionization energy of the hydrogen atom, 313.6 kcal/mole, is quite close to that of fluorine, so a covalent bond between these two atoms in HF is expected. Actually the properties of HF show that the molecule has a significant electric dipole, indicating ionic character in the bond. The same is true in the O—H bonds of water and, to a lesser extent, in the N—H bonds of ammonia. The ionic character of bonds to hydro-... 

Ammonia is a pungent, toxic gas that condenses to a colorless liquid at — 33°C. The liquid resembles water in its physical properties, including its ability to act as a solvent for a wide range of substances. Because the dipole moment of the NH3 molecule (1.47 D) is lower than that of the H20 molecule (1.85 D), salts with strong ionic character, such as KCI, cannot dissolve in ammonia. Salts with polarizable anions tend to be more soluble in ammonia than are salts with greater ionic character. For example, iodides are more soluble than chlorides in ammonia. Liquid ammonia undergoes much less autoprotolysis than water ... 

Both water and ammonia have four groups attached to their central atom and therefore both possess a tetrahedral electronic (or VSF PR) geometry. However, H20 has two unshared electron pairs while NH3 only has one, producing a larger dipole moment for H,0. 

This paper also reported results for three permanent dipole molecules, HC1, H20, and NH3, which exhibited an energy dependence of the specific rate constant in this energy range. The data for ammonia are typical and are presented in Figure 7. The points are experimental results,... 

If the bonds are ionic or ion-dipole bonds, the magnetic moments are those of the isolated central ions, given in the first column of moments in Table III. If the complex involves electron-pair bonds formed from sp alone, such as four tetrahedral sp3 bonds, the magnetic moments are the same, for the five d eigenfunctions are still available for the remaining electrons. The hydrazine and ammonia complexes mentioned above come in this class. 

Aminotrimethylenephosphonic acid 172 Ammonia 86,87 -, dipole moment 97 -, reagent 166 Ammonium cations 144 Ammonium rhodanide see Ammonium thiocyanate... 

Aminotriptyline lb 100-102 Amitrol lb 418 Ammonia la 86, 87,166 -, dipole moment la 97 Ammonium cations la 144 Ammonium compounds, quaternary lb 48,292,358 -, quaternary salts lb 48 Ammonium hydrogen carbonate, vapor la 86... 

Fig. 2. Components of Li enthalpies of complexation with methylamines. Successive steps indicate the effect on energy of interaction between Li and the amine of inclusion of additional components of the binding energy. The diagram shows that the permanent dipoles on amines (the charge on the nitrogen of the isolated amine) favor ammonia over trimethylamine complexation, but that polarizability and inductive effects (shift of negative charge onto the nitrogen in the complex) cause a massive turnaround in favor of complexation with trimethylamine rather than ammonia. Of particular importance is the near inversion of order caused by the addition of repulsive van der Waals terms. Modified after Ref. (9).

Figure 2.5 Bond moments and the resulting dipole moments of water and ammonia.

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