Covalent Bonding Interaction

The selection of the solvent is based on the retention mechanism. The retention of analytes on stationary phase material is based on the physicochemical interactions. The molecular interactions in thin-layer chromatography have been extensively discussed, and are related to the solubility of solutes in the solvent. The solubility is explained as the sum of the London dispersion (van der Waals force for non-polar molecules), repulsion, Coulombic forces (compounds form a complex by ion-ion interaction, e.g. ionic crystals dissolve in solvents with a strong conductivity), dipole-dipole interactions, inductive effects, charge-transfer interactions, covalent bonding, hydrogen bonding, and ion-dipole interactions. The steric effect should be included in the above interactions in liquid chromatographic separation. 

The quantum theory of atoms in molecules (QTAIM) [25, 26] is based on analyses of the electron density distribution. The electron density of such systems such as simple molecules or ions, and also complexes, complex molecular and ionic aggregates, as well as crystals may be analyzed using this approach. QTAIM is a powerful tool that allows characterizing of various interactions covalent bonds, ionic bonds, van der Waals interactions and, what is the most important for this review, also HBs. The analysis of critical points of the electron density is very useful. For the critical points (CPs), the gradient of electron density, p(r), vanishes ... 

In contrast to earlier polymer-supported complex catalysts in which complexes were immobilized through electrostatic interaction, covalent bonds, or coordinative bonds, in this case the complex is captured in Ihe elastomer network by occlusion in a dense polymer in Ihe absence of any supplementary chemical bonding and only as result of steric restrictions. In the hydrogenation of methyl acetoacetate by this catalyst an ee of 70% was obtained in polyethyleneglycol solution at 60 °C. Afer regeneration of the catalyst and reuse, its activity and enantioselectivity were almost unchanged. 

The survey over about 150 polymer crystals shows their distribution among seven crystal series. The number in the cubic crystal series is zero, because the c-axis contains completely different interactions (covalent bonds along the chain axis) from the other two axes (sub-valence interactions). The orthorhombic and the... 

The CP has been applied to the study of a wide variety of systems, including weak interacting systems such as van der Waals complexes, hydrogen bond complexes,and tight interactions (covalent bonds) such as molecular systems like In fact, it is now common practice to use some... 

---