Thermodynamic minimum

Aqueous solubility, potency and permeability are three factors under medicinal chemistry control that must be optimized to achieve a compound with acceptable oral absorption. Typically, a lead (chemistry starting point) is deficient in all three parameters. The inter-relationships of these three parameters has been described in a series of publications from Pfizer researchers [7, 8]. Figure 9.1 depicts graphically the minimum acceptable solubility as a function of projected clinical potency and intestinal permeability. A minimum thermodynamic aqueous solubility of 52... 

Chemical kinetic models require as a minimum thermodynamic and reaction-specific information. If problems involve transport, also proper transport coefficients are necessary. Since the accuracy of a kinetic model is often associated specifically with the chemical reaction mechanism, it is important to note that also the thermodynamic data are essential for the reliability of predictions. Fortunately the quality and quantity of data on thermochemistry of species and on the kinetics and mechanisms of individual elementary reactions have improved significantly over the past two decades, because of advances made in experimental methods. This has facilitated considerably our ability to develop detailed chemical kinetic models [356],... 

Figure 1. Minimum thermodynamic steam-methane ratio vs. temperature.

Bloom et al. [62] showed that the composition of complex ions in melts can differ from that of minimum conductivity, because the complex ions are in equilibrium with the simple ions, so that the maximum negative deviation from the additive conductivity would not correspond to the stoichiometry of the complex ions. Other researchers [63,64] found that the stoichiometry of complex ions is influenced by the maximum value of the activation energy. In any case, the electrical conductivity data must be correlated with other physicochemical data, such as phase diagrams, Raman spectra, minimum thermodynamic activities, to obtain the composition of complex ions. 

Figure 22.2 is a bar graph illustrating the minimum acceptable solubility as a function of compounds projected clinical potency and permeability in medicinal chemistry. The middle set of bars show that a compound has to have a minimum thermodynamic solubility of 52mg/mL when the permeability is average (avg and the projected clinical potency is 1 mg/kg. 

Minimum thermodynamically stable configuration Hexagonally packed sheets just touching Random close packing Body-centered cubic packing Face-centered cubic/hexagonal close packed... 

Fig. 1.1 Band structure of an n-type photoanode water splitting device, (a) Illustrating the various processes of photon irradiation, electron-hole pair formation, charge transport, and interfadal reactions, (b) Illustrating the energetic requirements associated with the minimum thermodynamic energy to split water, catalytic overpotentials for the HER and OER half-reactions, and photovoltage...

To analyze the energy-saving potential of distillation columns, it is customary to construct the temperature enthalpy and stage-enthalpy curves, called column grand composite curves. Column grand eomposite curves are based on the practical near-minimum thermodynamic condition approximation proposed by Dhole and... 

The previous treatment shows whether a particular system will mix or not, but in order to predict the equilibrium solubility, the thermodynamic potential must be calculated. The equilibrium solubility is at the point of minimum thermodynamic potential, and this point can be found by using treatments such as that of Flory and Huggins. The temperature effect on solubility is critical, as most solvents will not solvate iPP below 80°C. 

The creation of single, unassociated point defects in an elemental, crystalline solid increases the internal energy of the system and the enthalpy of the defect formation is positive. But the configurational entropy of the system also increases, and the equilibrium concentration of the defects will be reached when the Gibbs energy of the system is at minimum. Thermodynamically, point defects will thus always be present in a crystal above 0 K. 

Another major drawback of the high-pressure storage concept is the work required to compress the gas and time to deliver the compressed gas into the fuel tank. The minimum thermodynamic work of compression of gas for an internally reversible compressor (gas) or pump (liquid) per unit mass is [5]... 

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