Driving forces, thermodynamic

Polymers can be crystalline, but may not be easy to crystallize. Computational studies can be used to predict whether a polymer is likely to crystallize readily. One reason polymers fail to crystallize is that there may be many conformers with similar energies and thus little thermodynamic driving force toward an ordered conformation. Calculations of possible conformations of a short oligomer can be used to determine the difference in energy between the most stable conformer and other low-energy conformers. 

In the presence of oxygen and water the oxides of most metals are more thermodynamically stable than the elemental form of the metal. Therefore, with the exception of gold, the only metal which is thermodynamically stable in the presence of oxygen, there is always a thermodynamic driving force for corrosion of metals. Most metals, however, exhibit some tendency to passivate, ie, to form a protective oxide film on the surface which retards further corrosion. 

Do diffusion coefficient corrected for thermodynamic driving force, mvs... 

Complete wetting, i.e. spontaneous spreading should always be sought to maximize adhesion. This condition occurs when, with reference to Fig. 4, it is not possible to satisfy the horizontal force balance, i.e. ys > Vl + Ysl- The thermodynamic driving force for the spreading process is the spreading coefficient. 

A reversed, reductive TCA cycle would require energy input to drive it. What might have been the thermodynamic driving force for such a cycle Wachtershanser hypothesizes that the anaerobic reaction of FeS and H9S to form insoluble FeS9 (pyrite, also known as fool s gold) in the prebiotic milieu could have been the driving reaction ... 

In addition to molecular geometry, the most important quantity to come out of molecular modeling is the energy. Energy can be used to reveal which of several isomers is most stable, to determine whether a particular chemical reaction will have a thermodynamic driving force (an exothermic reaction) or be thermodynamically uphill (an endothermic reaction), and to ascertain how fast a reaction is likely to proceed. Other molecular properties, such as the dipole moment, are also important, but the energy plays a special role. 

Is the reaction as written exothermic, i.e., is there a thermodynamic driving force Rationalize your result. Is there an activation barrier to the reaction If so, is it typical of that of a thermal reaction (.04 to. 10 au or approximately 40-60 kcal/mol), much smaller or much larger ... 

Shown in Fig. 4a is the temperature dependence of the relaxation time obtained from the isothermal electrical resistivity measurement for Ni Pt performed by Dahmani et al [31. A prominent feature is the appearance of slowing down phenomenon near transition temperature. As is shown in Fig. 4b [32], our PPM calculation is able to reproduce similar phenomenon, although the present study is attempted to LIq ordered phase for which the transition temperature, T]., is 1.89. One can confirm that the relaxation time, r, increases as approaching to l/T). 0.52. This has been explained as the insufficiency of the thermodynamic driving force near the transition temperature in the following manner. 

The thermodynamic driving force behind the corrosion process can be related to the corrosion potential adopted by the metal while it is corroding. The corrosion potential is measured against a standard reference electrode. For seawater, the corrosion potentials of a number of constructional materials are shown in Table 53.1. The listing ranks metals in their thermodynamic ability to corrode. Corrosion rates are governed by additional factors as described above. 

In Eq. (4) the left-hand side (l.h.s.) expresses the thermodynamic driving force, while the right-hand side (r.h.s.) gives a structural, physical description of the interfacial region.5... 

Based on the preceding discussion on spillover-backspillover and in anticipation of Chapter 4 it is worth to briefly examine the thermodynamic driving force for ion (e.g. O2 ) backspillover between a solid electrolyte (e.g. YSZ) and the gas-exposed surface of a metal (e.g. Pt) electrode. 

Thus the difference jJ02-(S) Po2 (M) is the thermodynamic driving force for O2 backspillover from the support onto the catalyst surface as already discussed in Chapter 3 and as proven by AC Impedance spectroscopy, STM, TPD and XPS as reviewed in Chapter 5. It should be noted in equations (11.4) and (11.5) that the Fermi level of the metal is also the Fermi level of the support. 

This thermodynamic driving force is particularly useful tvith multienzyme equilibrium systems such as that used in the gram-scale synthesis of tv ro equivalents ofo-xylulose 5-phosphate (104) from (26) (Figure 10.38) [171,172]. Similarly, the corresponding 1-deoxy-D-xylulose 5-phosphate tvas efficiently produced from pyruvate and (34) by the catalytic action of the thiamine diphosphate-dependent 1-deoxy-D-xylulose 5-phosphate synthase (DXS) (EC 2.2.1.7) from E. coli [173]. 

The isomerisation of aUylic alcohols to saturated ketones usually has a strong thermodynamic driving force. The ruthenium NHC complex 62 has been used to catalyse the isomerisation of allylic alcohol 59 which gives ketone 60 as the principal product along with some of the reduction product 61 [32]. The catalyst was water-soluble and the aqueous phase could be re-used for several runs (Scheme 11.15). NHC analogues of Crabtree s catalyst, [IrlPCyjKpyridineXcod)] PFg, were found to be less efficient for the isomerisation of allylic alcohols than... 

Thns carbonyl chemistry can be considered as analogons to S l chemistry and is in fact inherently faster than 8 2 chemistry (not that 8 2 reactions cannot be fast, but this requires a strong thermodynamic driving force for a comparable driving force the carbonyl reaction is faster). 

The success of such reactions depends on the intramolecular hydrogen transfer being faster than hydrogen atom abstraction from the stannane reagent. In the example shown, hydrogen transfer is favored by the thermodynamic driving force of radical stabilization, by the intramolecular nature of the hydrogen transfer, and by the steric effects of the central quaternary carbon. This substitution pattern often favors intramolecular reactions as a result of conformational effects. 

The above important relationship now allows evaluation of the thermodynamic driving force of a redox reaction in terms of a measurable cell emf. Moreover, it is possible to utilize the relationship between the standard state potential and the standard state free energy to arrive at an expression for the equilibrium constant of a redox reaction in terms of the emf. Thus... 

Roush, D. J., Gill, D. S., and Willson, R. C., Anion-exchange chromatographic behavior of recombinant rat cytochrome b5. Thermodynamic driving forces and temperature dependence of the stoichiometric displacement parameter Z, /. Chromatogr., 653, 207, 1993. 

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