Solid synthesis kinetic control

Investigating the kinetically controlled synthesis of the /flactam antibiotic amoxicillin from 6-aminopenicillanic acid and D-p-hydroxyphenylglycine methyl ester in a solid suspension system in which the reaction nevertheless occurred in the liquid phase, Diender et al. found that the pH value and dissolved concentrations took a very different course at different initial substrate amounts (Diender, 2000). These results were described reasonably well by the model based on mass and charge balances, pH-dependent solubilities of the reactants, and enzyme kinetics. 

The solid materials obtained by these methods are always governed by the general thermodynamic laws represented by the phase diagrams. In contrast, the methodologies included in the phrase Chimie Douce involve kinetic control of the solid synthesis when non-reversible reactions are used. Therefore, solids prepared by this route are not the most... 

Hybrid framework compounds, including both metal-organic coordination polymers and systems that contain extended inorganic connectivity (extended inorganic hybrids), have recently developed into an important new class of solid-state materials. We examine the diversity of this complex class of materials, propose a simple but systematic classification, and explore the chemical and geometrical factors that influence their formation. We also discuss the growing evidence that many hybrid frameworks tend to form under thermodynamic rather than kinetic control when the synthesis is carried out under hydrothermal conditions. Finally, we explore the potential applications of hybrid frameworks in areas such as gas separations and storage,... 

In custom-designing materials with tailored properties, it is often necessary to s)m-thesize metastable phases that will be kinetically stable under the temperature and conditions of use. These phases are obtainable only through kinetic (chemical) control. In many cases, kinetic control has been achieved via the soft chemical low-temperature (e.g. electrochemical synthesis, sol-gel method) and/or topochemical routes (e.g. intercalation, ion exchange, dehydration reactions), since these routes use nuld synthetic conditions. It should be noted that not all soft chemical routes are topochemical. A reaction is said to be under topochemical control only if it follows the pathway of minimum atomic or molecular movement (Elizabe et al., 1997). Accordingly, topochemical reactions are those in which the lattice of the solid product shows one or a small number of... 

Intercalation reactions and intercalation compounds have attracted attention for several reasons. Reactions provide routes for the synthesis of new solids with kinetic rather than thermodynamic stability and permit controlled systematic changes in physical properties, particularly the electronic, magnetic, and optical properties of the host lattice. Chemical properties may also be finely tnned by incremental changes in... 

In fact, since the mesophase synthesis or reaction is a kinetically control process and the solid formed is not a thermally stable phase, the phase transformation is very common during the synthesis of mesoporous materials. The phase transformations include the transition from one structure or symmetry into another structure or symmetry, or the transition from a disordered phase to an ordered phase, or from an ordered phase to a disordered phase. The intermediate phase can be isolated as a product or be observed by analysis techniques. The phase transformation can occur during the synthesis process or in a post-synthesis treatment. The early famous example is the transition of lamellar mesophase of silicate into hexagonal mesophase in basic or near neutral media.[5]... 

Moreover, this method appears suitable for the synthesis of phosphine-substituted molecular clusters of different nuclearity, depending on which phosphine is used. The availability of these clusters offers the opportunity to exert a stoichiometric control in those processes that lead from molecular metal chalcogenides such as [MxEy(PR3) ,J to extended inorganic solids like MxEy. The stoichiometric control, combined with the kinetic control, which derives from low activation energies of these processes, often allows the preparation of otherwise inaccessible solid phases or microinhomogeneous materials such as nanocomposites. ... 

The interest in intercalation reactions stems from different motivations. From a preparation point of view they provide routes for the systematic synthesis of new solids with kinetic rather than thermodynamic stability that cannot be obtained by other preparation techniques [11, 13], Furthermore, they permit controlled systemic modifications of chemical as well as physical properties, including electronic, magnetic and optical properties. From an application viewpoint, they are of importance in supercapacitors, rechargeable batteries, non-emissive electrochromic displays, and so forth [4, 14],... 

Most radicals are transient species. They (e.%. 1-10) decay by self-reaction with rates at or close to the diffusion-controlled limit (Section 1.4). This situation also pertains in conventional radical polymerization. Certain radicals, however, have thermodynamic stability, kinetic stability (persistence) or both that is conferred by appropriate substitution. Some well-known examples of stable radicals are diphenylpicrylhydrazyl (DPPH), nitroxides such as 2,2,6,6-tetramethylpiperidin-A -oxyl (TEMPO), triphenylniethyl radical (13) and galvinoxyl (14). Some examples of carbon-centered radicals which are persistent but which do not have intrinsic thermodynamic stability are shown in Section 1.4.3.2. These radicals (DPPH, TEMPO, 13, 14) are comparatively stable in isolation as solids or in solution and either do not react or react very slowly with compounds usually thought of as substrates for radical reactions. They may, nonetheless, react with less stable radicals at close to diffusion controlled rates. In polymer synthesis these species find use as inhibitors (to stabilize monomers against polymerization or to quench radical reactions - Section 5,3.1) and as reversible termination agents (in living radical polymerization - Section 9.3). 

M. Erbeldinger, X. Ni, and P. J. Halling, Kinetics of enzymatic solid-to-solid peptide synthesis synthesis of Z-aspartame and control of acid-base conditions by using inorganic salts, Biotechnol. Bioeng. 2001, 72, 69-76. 

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