Equilibrium controlled processe

Hydrolysis (Sections 20 10 and 20 11) Ester hydrolysis may be catalyzed either by acids or by bases Acid catalyzed hydrolysis is an equilibrium controlled process the reverse of the Fischer esterification Hydrolysis in base IS irreversible and is the method usual ly chosen for preparative purposes... 

Evidence was then obtained that protonation of the oxygen atom is a rapid, equilibrium-controlled process - and that the slow, rate-determining, heterolysis step is unimolecular these facts are consistent with both A-1 mechanisms (see equation 3) and eliminate aU others. (A third mechanism has, however, been proposed by Rydon and coworkers for the hydrolysis of some aryl glycosides it is discussed in Section IV,2 see pp. 79-81). 

Melt process. Also referred to by other names including high melt, bulk melt, bulk, or neat. The melt process is an equilibrium-controlled process in which polymer is formed by driving the reaction toward completion, usually through removal of the byproduct or condensate. Thus, in the reaction of a diacid and a diol to form a polyester, water is removed, causing the reaction to proceed towards polymer formation. The reactants are employed neat (without solvent) any other needed materials such as catalysts are added to the reaction vessel. Heat is applied to melt the reactants, permitting them to come into contact with one another. Additional heat can be added and the pressure reduced, but heat control is important since most of these reactions are exothermic. These reactions typically take several hours to days before the desired polymer is formed. The product yield is necessarily high. 

The ability of such a reactor to circumvent thermodynamic limitation of an equilibrium-controlled process allows the same reactants conversion to be obtained at a lower temperature or a higher conversion to be reached at the same temperature. 

Modern theoretical models used to describe SEC elution behavior must allow for possible variations in both the solute and bead pore size and shape, while remaining consistent with current concepts regarding SEC as an equilibrium controlled process. SEC, then, may be explained on the basis of purely geometrical arguments (ref. 16). We shall examine the historical development of these models next. 

An important feature of the halogen/metal interconversion is that it is an equilibrium-controlled process, which is therefore shifted toward the most stable organolithium or organomagnesium reagent or, to put it in other words, toward the weakest base [18-20],... 

Proteases for peptide synthesis are selected on the basis of their specificity against amino acid residues and include the majority of the commercially available proteases of the four classes mentioned above [58]. Protease-catalyzed bond synthesis can be carried out either as an equilibrium-controlled process which is the direct reversal of the protease-catalyzed hydrolysis or a kinetically controlled process. In the latter case weakly activated carboxy components are employed [61]. 

The important question as to whether the chemical steps involved in the transient oxygen storage and release processes previously described (Sections 3.3.1 and 3.3.2) should be considered as equilibrium controlled processes (reversible elementary steps) has recently been addressed. It was found that reduction of ceria by CO or Hg to form COg or HgO, respectively, is very important, and if not included in proposed reaction schemes, a number of effects experimentally observed under the dynamic conditions of OSC measurement cannot be understood. For example (i) the observed OSC is lower in the presence of HgO and COg in the CO/He and Og/He alternate pulse or step-change gas compositions (ii) the observed OSC depends on the CO/Hg concentration (iii) when the catalyst is exposed to a rich-lean step, the outlet gas composition remains rich for some time after the inlet has switched to lean (iv) when a previously oxidized catalyst is subjected to a short rich pulse followed by stoichiometric operation, the catalyst emits a delayed pulse of CO/ Hg during the stoichiometric phase (v) when a catalyst is operated with an oscillating air/fuel ratio at slightly rich conditions, the... 

This simple analysis for an isothermal and equilibrium controlled process can be extended to concentrated systems in which u must remain within the differential of the second term in equation (6.19). The analysis can also be extended to systems which include more than a single adsorbable component. Consider the case of a feed stream which contains only two adsorbable components, i.e. a system which does not include a non-adsorbing carrier fluid. In this case both components can be ejqiected to be concentrated in the fluid and hence the variation in fluid velocity over the MTZ must be taken into account. Two differential fluid phase mass balance equations must be written, one for each component. Equation (6.31) is shown for component 1. The axial dispersion term is retained to create a general equation. 

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