Chemical deductive solution

The logical and combinatorial chemical applications of computers are based on integer computation. Storage, retrieval and manipulation of data as well as deductive operations by computers are in that category. Chemical documentation, information oriented synthesis design, and the deductive solution of chemical problems are examples. In the deductive solution of chemical problems the solutions of the individual problems are deduced from general principles. 

THE DEDUCTIVE SOLUTION OF CHEMICAL PROBLEMS AND THE THEORY OF THE BE- AND R-MATRICES... 

The theory of the BE- and R-matrices serves as the theoretical foundation of computer programs for the deductive solution of a variety of chemical problems. Such programs are under development at our institute since 1971 (ref. 4). Our present generation of interactive problem-solving FORTRAN 77 programs for PCs evolved in the past three years from our earlier batch type PL/I programs for mainframe computers (ref. 12). 

The development of PVC illustrates the interplay of logic and serendipity, as well as the importance of optimizing properties both for processing and for applications. PVC production has been beset with difficulties from the beginning, but solutions have been found for each problem through a combination of chemical deduction and trial and error. For example, many additives have been found that provide temperature stability so that PVC can be processed as a melt (liquid) and so that PVC products can be used at high temperatures. However, there is still controversy among chemists about exactly how PVC decomposes thermally, and thus the reason these stabilizers work is not well... 

Computer Programs for the Deductive Solution of Chemical Problems on the Basis of a Mathematical Model of Chemistry... 

In the present paper a simple mathematical model of the chemistry of a given set of atoms is presented which afford s precisely the latter, and may serve as a basis of computer programs for the deductive solution of a great variety of chemical problems. 

The mathematical model of constitutional chemistry which has been described in the preceeding sections can be used as a basis for a modular system of computer programs for the deductive solution of chemical problems. 

Dugundji, Ugi, and his coworkers (Dugundji and Ugi, 1973 Ugi et al, 1979, 1990) used the bond-electron matrices BE and the reaction matrices RM as a basis for computer programs for the deductive solution of a variety of chemical problems, such as the classification and documentation of structures, substructures, and reactions, the prognosis of reaction products, the design of synthetic routes, the construction of netwoiks of mechanistic and preparative pathways, the prediction of chemical reactions, etc. 

The deduction adopted is due to M. Planck (Thermodynamik, 3 Aufl., Kap. 5), and depends fundamentally on the separation of the gas mixture, resulting from continuous evaporation of the solution, into its constituents by means of semipermeable membranes. Another method, depending on such a separation applied directly to the solution, i.e., an osmotic process, is due to van t Hoff, who arrived at the laws of equilibrium in dilute solution from the standpoint of osmotic pressure. The applications of the law of mass-action belong to treatises on chemical statics (cf. Mel lor, Chemical Statics and Dynamics) we shall here consider only one or two cases which serve to illustrate some fundamental aspects of the theory. 

Chemical kinetics deductions are, in some circumstances, possible from a reaction system using a dispersed solid. If the solid is entirely insoluble, for example a supported catalyst, true surface kinetics can be obtained provided (i) it can be shown that the chemical reaction on the surface is much slower than the associated mass transfer, and (ii) the surface area of the solid can be obtained. These conditions applied in the case of the oxidation of an aqueous solution of hydrazine using a dispersion of insoluble barium chromate [16]. Another case is where it can be shown that an increase in the amount of the solid component does not increase the reaction rate. In this case, exemplified by the formation of benzyl acetate from benzyl bromide and solid sodium acetate in toluene solvent, it is likely that the reaction occurs in the solution phase and that the reaction is proceeding at the saturation concentration of the solid reactant in the liquid phase [17]. 

It was our aim to study the chemistry of NMMO and Lyocell solutions in order to put the prevention of undesired side-effects on a more scientific foundation [8,9]. The improved understanding of the individual chemical processes in Lyocell solutions today allows an accurate deduction of the different tasks of optimum Lyocell stabilizers. The question of which reactive intermediates are involved in the degradation processes of both NMMO as the solvent and cellulose as the solute was a key issue in the studies of Lyocell chemistry. 

A hierarchic classification of chemical reactions is implied by the theory of the BE-and R-matrices (ref. 9). This classification is a powerful device in the deductive computer assisted solution of chemical problems. 

This mathematical model can serve as a basis for a variety of deductive computer programs for the solution of chemical problems6-8. From among all the possibilities, synthetic planning was chosen first — for reasons stated before — and the computer program CICLOPS (Computers in Chemistry, Logic Oriented Planning of Synthe-... 

ACTIVITY AND ACTIVITY COEFFICIENTS In our deduction of the law of mass action we used the concentrations of species as variables, and deduced that the value of the equilibrium constant is independent of the concentrations themselves. More thorough investigations however showed that this statement is only approximately true for dilute solutions (the approximation being the better, the more dilute are the solutions), and in more concentrated solutions it is not correct at all. Similar discrepancies arise when other thermodynamic quantities, notably electrode potentials or chemical free energies are dealt with. To overcome these difficulties, and still to retain the simple expressions derived for such quantities, G. N. Lewis introduced a new thermodynamic quantity, termed activity, which when applied instead of concentrations in these thermodynamic functions, provides an exact fit with experimental results. This quantity has the same dimensions as concentration. The activity, aA, of a species A is proportional to its actual concentration [A], and can be expressed as... 

Coetzee and C. D. Ritchie (eds.) Solute-Solvent Interactions, Dekker, New York, 1969, Vol. 1, p. 344ff. [447] P. M. Laughton and R. E. Robertson Solvent Isotope Effects for Equilibria and Reactions, in J. F. Coetzee and C. D. Ritchie (eds.) Solute-Solvent Interactions, Dekker, New York 1969, Vol. 1, p. 399ff. [448] C. J. Collins and N. S. Bowman (eds.) Isotope Effects in Chemical Reactions, Van Nostrand Reinhold, New York, 1970, p. 246 and 266ff. [449] R. L. Schowen Mechanistic Deductions from Solvent Isotope Effects, Progr. Phys. Org. Chem. 9, 275 (1972). [450]... 

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