Determination of molecular packing

Equation (13) can also be used for the calculation of molecular diameters from experimental viscosity data. These can be compared with molecular diameters as determined by other experimental methods (molecular beams, diffusion, thermal conductivity, x-ray crystallographic determination of molecular packing in the solid state, etc.). 

DETERMINATION OF MOLECULAR PACKING AND ORIENTATION IN ULTRATHIN FILMS ANISOTROPIC OPTICAL CONSTANTS OF ULTRATHIN FILMS... 

In the absence of defects, the reactivity of organic solids is mainly determined by molecular packing. Reactions in which the crystal structure holds sway over intrinsic molecular reactivity are said to be topochemically controlled (Thomas, 1974). A classic example of a topochemically controlled organic reaction in the solid state is the photodimerization of rrans-cinnamic acids studied by Schmidt et al. (see Ginsburg,... 

Knowledge of the effective molecular area is of particular importance when gas adsorption is used for the determination of surface area (see Chapter 6). It is often assumed that the completed monolayer is in a liquid close-packed state, but it is now apparent that we must question the soundness of this assumption. The recent studies of phase transitions and monolayer structures lead us to the conclusion that the degree of molecular packing is dependent on the adsorption system (both adsorbent and adsorptive) and the operational conditions of pressure and temperature (Steele, 1996). 

A second type of adsorption is called chemisorption. In this case, the adsorption energy is comparable to the chemical bond energies and adsorbate molecules have the tendency to be localized at particular sites even though surface diffusion or some molecular mobility may still occur. Due to the chemical nature of the interactions between the gas and the solid surface, the equilibrium gas pressure in the adsorption system can be extremely low. This enables one to study the adsorbent-adsorbate system under high vacuum using diffraction and spectroscopic techniques for the identification of the actual species presented on the surface and the determination of their packing and chemical state. 

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