Electric polarization small molecules

One anomaly inmrediately obvious from table A2.4.2 is the much higher mobilities of the proton and hydroxide ions than expected from even the most approximate estimates of their ionic radii. The origin of this behaviour lies in the way hr which these ions can be acconmrodated into the water structure described above. Free protons cannot exist as such in aqueous solution the very small radius of the proton would lead to an enomrous electric field that would polarize any molecule, and in an aqueous solution the proton inmrediately... 

Non-polar Solutes in Polar Solvents the (Solvent Stark EffecP. At first sight a non-polar solute molecule cannot polarize the surrounding solvent since it develops no electric field. However, the solvent fluctuates around the non-polar solute, so that there is a small instantaneous electric field which acts on the solute to produce a fluctuating induced dipole which leads to... 

However the precise sequence of coordinate participation in the reaction path is solvent dependent. For the case just discussed, the water solvent is rapid, largely because of the small moment of inertia involved in the water molecule reorientations underlying the change of the electrical polarization. Dimethyl formamide (DMF) solvent is less rapid, and the resulting coordinate sequence on the way to the TS [3] is again in the order of decreasing slowness, but now the solvent coordinate is the slowest of the three, followed by the bend angle and finally the C - Cl bond stretch. The reaction path depends on the solvent time scale. 

When a substance is placed in an electric field, such as exists between the plates of a charged capacitor, it becomes to some extent electrically polarized. The polarization results at least in part from a displacement of electron clouds relative to atomic nuclei polarization resulting from this cause is termed electronic polarization. For molecular substances, atomic polarization may also be present, owing to a distortion of the molecular skeleton. Taken together, these two kinds of polarization are called distortion polarization. Finally, when molecules possessing permanent dipoles are present in a liquid or gas, application of an electric field produces a small preferential orientation of the dipoles in the field direction, leading to orientation polarization. 

Dipole rotation refers to the alignment, by effect of the electric field, of molecules in the sample that have permanent or induced dipole moments. As the electric field of microwave energy increases, it aligns polarized molecules. As the field decreases, thermally induced disorder is restored. In fact, applied microwave fields cause molecules, on average, to temporarily spend very slightly more time pointing in one direction than in others. Associated with that very small fraction of preferred orientation there is another very small fraction of molecular order imposed and hence a tiny bit of energy. When the... 

Abstract. The paper provides analysis of a process, when a laser radiation absorption of a specific polarization creates a specific spatial distribution of molecular bonds and angular momenta of small molecules. It is discussed how an external fields electric or magnetic can influence this distribution. Some practical examples involving optical polarization of molecules in magnetic and electric fields are presented. ... 

A classification scheme for molecular polarity can be based on the electric potential surrounding the molecule. Traditionally, schemes for ranking molecular polarity are based on electronegativity differences, on molecular dipole moments, or on solubility. The root-mean-square (rms) value of the molecular electric potential can be used for this purpose. Table 1 shows a ranking of 24 small molecules according to their rms electric potential. Note that all of the amides are extremely polar by this criterion, more polar than formaldehyde or water. Hydrogen fluoride is less polar than acetone, acetaldehyde, water, or the amides. At the low end of the polarity scale, the amines are surprisingly nonpolar. As expected acetylene is more polar than ethylene, which is more polar than methane. 

It is not in general possible for neutral atoms or molecules to be bound in ionic crystal structures, but the molecule of water, and to a lesser extent that of ammonia, are exceptions to this general rule. The reason for this anomalous behaviour lies primarily in the electrical polarity and small size of these molecules. The particular relevance of these two factors will appear as our discussion proceeds. 

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