Reaction pathways quantitative reasoning

Michael L. Mavrovouniotis, Symbolic and Quantitative Reasoning Design of Reaction Pathways through... 

The Conceptual Synthesis of Chemical Processing Schemes Michael L. Mavrovouniotis, Symbolic and Quantitative Reasoning Design of Reaction Pathways through Recursive Satisfaction of Constraints Christopher Nagel and George Stephanopoulos, Inductive and Deductive Reasoning ... 

SYMBOLIC AND QUANTITATIVE REASONING DESIGN OF REACTION PATHWAYS THROUGH RECURSIVE SATISFACTION OF CONSTRAINTS... 

Given a fixed, predetermined set of elementary reactions, compose reaction pathways (mechanisms) that satisfy given specifications in the transformation of available raw materials to desired products. This is a problem encountered quite frequently during research and development of chemical and biochemical processes. As in the assembly of a puzzle, the pieces (available reaction steps) must fit with each other (i.e., satisfy a set of constraints imposed by the precursor and successor reactions) and conform with the size and shape of the board (i.e., the specifications on the overall transformation of raw materials to products). This chapter draws from symbolic and quantitative reasoning ideas of AI which allow the systematic synthesis of artifacts through a recursive satisfaction of constraints imposed on the artifact as a whole and on its components. The artifacts in this chapter are mechanisms of catalytic reactions and... 

The discovery and characterization of the thiyl/thiolate conjugation equilibrium (3) [14] is one of the most significant contributions of the pulse radiolysis technique to the chemistry of cellular oxidative stress. Without such measurements, including the direct observation of the reduction of thiyl radicals by ascorbate [13] and electron transfer from disulphide radical anions to oxygen [ 15], it would be indeed difficult to prepare a reasoned argument for the competing reaction pathways from a quantitative viewpoint. Further work is needed to develop these concepts further. Not least, the dimension of space (as well as an appreciation of interfacial phenomena) needs to be added to the dimension of time if we are to model realistically the cellular environment and assess quantitatively, for example, the importance of the synergy between the lipophilic phenolic antioxidant, vitamin E and the hydrophilic electron-donor, vitamin C (ascorbate) [134]. 

Most of the substitution reactions with the homoleptic Tc(I) isocyanide complexes presented in the preceding section had to be performed at elevated temperatures and were often characterized by low yield. The reason for this behaviour is the exceptionally high kinetic and thermodynamic stability of this class of compounds. From this point of view, 4a are not very convenient or flexible starting materials, although they are prepared directly from 3a in quantitative yield. The exceptionally high kinetic and thermodynamic stability is mirrored by the fact that it was not possible to substitute more than two isocyanides under any conditions. On the other hand, oxidation to seven-coordinated Tc(III) complexes occurs very readily. Technetium compounds of this type, which are not expected to be very inert, could open up a wide variety of new compounds, but this particular field has not been investigated very thoroughly. A more convenient pathway to mixed isocyanide complexes that starts with carbonyl complexes of technetium will be described in Sects. 2.3 and 3.2. 

Molecular dynamics simulations are attractive because they can provide not only quantitative information about rates and pathways of reactions, but also valuable insight into the details of ho y the chemistry occurs. Furthermore, a dynamical treatment is required if the statistical assumption is not valid. Yet another reason for interest in explicit atomic-level simulations of the gas-phase reactions is that they contribute to the formulation of condensed-phase models and, of course, are needed if one is to include the initial stages of the vapor-phase chemistry in the simulations of the decomposition of energetic materials. These and other motivations have lead to a lot of efforts to develop realistic atomic-level models that can be used in MD simulations of the decomposition of gas-phase energetic molecules. 

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