Repulsion, molecular

The term "hydrophobic interaction" unfortunately implies some form of molecular repulsion, which, outside the van der Waals radii of a molecule, is quite impossible. The term "hydrophobic force" literally means "fear of water" force. The term hydrophobic has been introduced as an alternative to dispersive but means the same. It is not clear from the literature how the word hydrophobic originated, but it may have been provoked by the immiscibility of a dispersive solvent such as n-heptane with a very polar solvent such as water. 

Molektil, Molekel, n. molecule. Molekular-abstosstmg, /. molecular repulsion. 

P (r) is the attractive contribution important at large separations. (This same notion is used in the van der Waals equation of state, in which the constant a accounts for molecular attraction and b for molecular repulsion.)... 

Pressure—a reflection of the number of molecules present and their motion, temperature—a reflection of the kinetic energy of the molecules, and molecular attraction and repulsion. Pressure and molecular attraction tend to confine the molecules and pull them together. Temperature and molecular repulsion tend to separate the molecules. 

Molecular Repulsion at Extreme Close Approach Eigure 2.6, Table 2.2 van der Waals Radius Hydrogen Bonds (Eigure 2.7)... 

The term "hydrophobic" is a most unfortunate term in that it implies some form of molecular repulsion, which, of course, outside the van der Waals radii of a molecule, is impossible. The term "hydrophobic force". 

Here, the first and second terms describe correspondingly positive pressure due to molecular repulsion and negative pressure due to molecular attractive forces. Our task is to understand the microscopic sense of parameters p/, (index means hard spheres) and /q. Therefore we need a proper partition function. 

Alternatively, the results can be represented by plotting p(r) against r, which shows the peaks more clearly. The curve obtained is shown in Fig. 1.5(b), where Po is the mean number density of molecules in the liquid. The p(r) curve starts from zero and rises sharply at a finite value of r as a consequence of the molecular repulsions. It then passes through a maximum and oscillates about the value po, tending to the value Po at large values of r. The first maximum corresponds to the shell of nearest neighbours and gives the approximate molecular diameter. 

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