Alkane molecules, interaction between

The system used in the simulations usually consists of solid walls and lubricant molecules, but the specific arrangement of the system depends on the problem under investigation. In early studies, hard spherical molecules, interacting with each other through the Lennard-Jones (L-J) potential, were adopted to model the lubricant [27], but recently we tend to take more realistic models for describing the lubricant molecules. The alkane molecules with flexible linear chains [28,29] and bead-spring chains [7,30] are the examples for the most commonly used molecular architectures. The inter- and intra-molecular potentials, as well as the interactions between the lubricant molecule and solid wall, have to be properly defined in order to get reliable results. Readers who intend to learn more about the specific techniques of the simulations are referred to Refs. [27-29]. 

Dispersion forces, dipole Interactions, and hydrogen bonds all are significantly weaker than covalent Intramolecular bonds. For example, the average C—C bond energy Is 345 kJ/mol, whereas dispersion forces are just 0.1 to 5 kJ/mol for small alkanes such as propane. Dipolar Interactions between polar molecules such as ace-tone range between 5 and 20 kJ/mol, and hydrogen bonds range between 5 and 50 kJ/mol. 

Hydrogen bonding and electrostatic interactions between the sample molecules and the phospholipid bilayer membranes are thought to play a key role in the transport of such solute molecules. When dilute 2% phospholipid in alkane is used in the artificial membrane [25,556], the effect of hydrogen bonding and electrostatic effects may be underestimated. We thus explored the effects of higher phospholipid content in alkane solutions. Egg and soy lecithins were selected for this purpose, since multicomponent mixtures such as model 11.0 are very costly, even at levels of 2% wt/vol in dodecane. The costs of components in 74% wt/vol (see below) levels would have been prohibitive. 

Hydrogen bonding and electrostatic interactions between the sample molecules and the phospholipid bilayer membranes are thought to play a key role in the transport of such molecules. When dilute 2% wt/vol phospholipid in alkane is used in the artificial membrane [15, 23], the effect of hydrogen bonding and electrostatic effects may be underestimated. 

The solubility of molecules can be explained on the basis of the polarity of molecules. Polar, e.g. water, and nonpolar, e.g. benzene, solvents do not mix. In general, like dissolves like i.e., materials with similar polarity are soluble in each other. A polar solvent, e.g. water, has partial charges that can interact with the partial charges on a polar compound, e.g. sodium chloride (NaCl). As nonpolar compounds have no net charge, polar solvents are not attracted to them. Alkanes are nonpolar molecules, and are insoluble in polar solvent, e.g. water, and soluble in nonpolar solvent, e.g. petroleum ether. The hydrogen bonding and other nonbonding interactions between molecules are described in Chapter 2. 

For the primary interaction sequence between Hg 6(sPi) atoms and alkane molecules, the experimental evidence has now been given in some... 

The reason for the experimentally proven lipophobicity, i.e., the tendency of fluorinated and hydrogenated chains to phase separate, is much less clear than the other effects of fluorination and is still under debate. Mostly it is assigned to the disparity of cohesive energy densities between perfluoroalkanes and alkanes. A reduction of ca. 10% in the interactions between unlike pairs of molecules was estimated by several methods [90]. However, there are also simulations suggesting slightly stronger attractive contributions to the interaction between Rf/Rh pairs compared to the like interactions under certain circumstances [94]. 9 However,... 

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