Equilibrium position factors controlling

This interconversion can also be performed in solvents, and the rate of the isomerization is dependent on the solvent used. In the dipolar aprotic solvent DMSO the rate of the reaction is fast, but in methanol, acetone, or dioxane the rate is low. However, the value of the equilibrium constant is scarcely influenced by the solvent ( 134/133 = 6-10) (75JHC985).This is not too surprising, since the equilibrium position is controlled by the relative thermodynamic stability of the isomers, which is a function of their heats of formation and of solvation. Undoubtedly, the heat of formation is the more important factor to the thermodynamic stability (75JHC985). 

For the equilibrium-controlled enzyme-catalyzed peptide synthesis the equilibrium position lies far over in the direction of the hydrolysis, and under physiological conditions, the product yield is negligible. The equilibrium position is determined exclusively by thermodynamic factors and like any other catalysts the enzymes only accelerate the attainment of the equilibrium. 

We also saw in Section 12.16 that lithium, although it is the strongest reducing agent, reacts more slowly with water than sodium or potassium. From the discussions in Chapters 10 and 15, we know that the equilibrium position for a reaction (in this case indicated by the %° values) is controlled by thermodynamic factors, but that the rate of a reaction is controlled by kinetic factors. There is no direct connection between these factors. Lithium reacts more slowly with water than sodium or potassium because as a solid lithium has a higher melting point than either of the other elements. Since lithium... 

The equilibrium position is strongly affected by a variety of factors, and can be shifted to either extreme under suitable conditions. It is thus possible to effectively control the coordination number of silicon to be either 5 or 6, in a reversible manner, and to modify the complex s properties accordingly. This may prove useful in the future design of molecular switches. 

The relaxation time of those polarizations are governed by different factors. For the electronic polarization the relaxation time is comparable to the speed of light. Tlie relaxation time of atomics (ions) is comparable to the vibration frequency of each ion. The relaxation time of the Debye polarization is controlled by the potential barrier between two equilibrium positions where the dipole would orientate from one to other [10[. The relaxation time of the Debye polarization, tj, can be expressed as [10] ... 

It follows that the position of thermodynamic equilibrium will change along the reactor for those reactions in which a change of tire number of gaseous molecules occurs, and therefore that the degree of completion and heat production or absorption of the reaction will also vaty. This is why the external control of the independent container temperature and the particle size of the catalyst are important factors in reactor design. 

It is important to understand the factors that control the position of a chemical equilibrium. For example, when a chemical is manufactured, the chemists and chemical engineers in charge of production want to choose conditions that favor the desired product as much as possible. In other words, they want the equilibrium to lie far to the right. When Fritz Haber was developing the process for the synthesis of ammonia, he did extensive studies on how the temperature and pressure affect the equilibrium concentration of ammonia. Some of his results are given in Table 6.2. Note that the amount of NH3 at equilibrium increases with an increase in pressure but decreases with an increase in temperature. Thus the amount of NH3 present at equilibrium is favored by conditions of low temperature and high pressure. 

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