Ammonia electrostatic potential

Examine the models of ammonia and pyridine on your Learning By Modeling CD. Are the calculated charges on nitrogen consistent with their relative basicities What about their electrostatic potential maps ... 

Examine atomic charges and display electrostatic potential maps for ammonium and trimethylammonium ions (protonated ammonia and trimethylamine, respectively). How many acidic hydrogens are there in each Assuming that solvent coordinates to acidic hydrogens, how many solvation sites are there in each ... 

Calculate activation energies for Sn2 reactions of ammonia and trimethylamine with methyl iodide via transition states ammonia+methyl iodide and trimethyl-amine+methyl iodide, respectively. Is attack by ammonia or trimethylamine more facile Rationalize your observation by comparing electrostatic potential maps for the two transition states. Which transition state requires more charge separation Is this also the higher-energy transition state ... 

Electrostatic potential map—cont d ammonia, 145 aniline, 925 anilinium ion, 925 anisole, 111 18]annulene, 535 arene, 74 azulene, 541 benzaldehyde, 565, 704 benzene, 44, 521, 565 benzenediazonium ion, 945 benzoquinone, 631 benzyl carbocation, 377 benzyne, 576 borane, 223... 

Figure 3.2 The effect of increasing electronegativity among elements from left to right in the first row of the periodic table is evident in these electrostatic potential maps for methane, ammonia, water, and hydrogen fluoride.

The reactions of chlorobenzene and benzaldehyde with ammonia over metal Y zeolites have been studied by a pulse technique. For aniline formation from the reaction of chlorobenzene and ammonia, the transition metal forms of Y zeolites show good activity, but alkali and alkaline earth metal forms do not. For CuY, the main products are aniline and benzene. The order of catalytic activity of the metal ions isCu> Ni > Zn> Cr> Co > Cd > Mn > Mg, Ca, Na 0. This order has no relation to the order of electrostatic potential or ionic radius, but is closely related to the order of electronegativity or ammine complex formation constant of metal cations. For benzonitrile formation from benzaldehyde and ammonia, every cation form of Y zeolite shows high activity. 

Use SpartanView to compare electrostatic potential maps of the reactants and the transition state for the Sfj2 reaction of ammonia with iodomethane. Which is more polar How would the reaction rate change if a polar aprotic solvent such as DMSO were replaced with a polar protic solvent such as water ... 

FIGURE 10.10 (a) Space-filling models, (b) 0.002 e/(ao) electron density isosurfaces, and (c) electrostatic potential energy surfaces for water, ammonia, and methane. 

F.M. Abu-Awad, A comparative study of the structure and electrostatic potential of H-bonded clusters of neutral ammonia (NII3) ( = 2-6). J. Mol. Struct. (THEOCHEM) 683, 57-63, 2004, and references therein. 

V. Dimitrova, S. Ilieva, and B. Galabov, Electrostatic potential at atomic sites as a reactivity descriptor for hydrogen bonding. Complexes of monosubstituted acetylenes and ammonia, J. Phys. Chem. A 106, 11801-11805 (2002). 

For the ammonia molecule (II), isoelectronic with water, the electrostatic potential has a shape which is shown in part in Fig. 45>. The figure... 

Let us consider first a small molecule, ammonia, for which the most obvious expansion choice is the one-center one. To verify the behaviour of the a) expansion with the distance, a set of concentric spheres (centered at the nuclear charge center) was selected, and on each sphere a set of 614 equally spaced points 50>. The electrostatic potential was calculated for each of these points, according to either the exact SCF formula (Eq. 13) or the multipole expansion (as in Eq. 17). The expansion was progressively extended, first including only the dipole term, then the quadrupole, the octopole and finally the hexadecapole ones. The mean values of W (r) on each sphere are reported in Fig. 47 as a function of the radius R. For distances greater than 2 A, an expansion truncated after the octopole terms may be considered sufficiently accurate. 

Fig. 47. Convergency properties of the multipole expansion of electrostatic energy. 1F(R) is the mean value of electrostatic potential on a sphere of radius R calculated by a) dipole expansion terms only, b) dipole and quadrupole, c) dipole, quadrupole and octopole terms, d) as c) plus hexadecapole terms e) SCF values. The left side of figure refers to ammonia, the right one to aziridine...

Fig. 48. Variation with the distance of the percentage mean value of the error for one-center (solid lines) and many-center (broken lines) expansions of the electrostatic potential a) water, b) ammonia, c) aziridine. From Ref. 50>...

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