Similarity of reactions

Reactions can be considered as composite systems containing reactant and product molecules, as well as reaction sites. The similarity of chemical structures is defined by generalized reaction types and by gross structural features. The similarity of reactions can be defined by physicochemical parameters of the atoms and bonds at the reaction site. These definitions provide criteria for searching reaction databases [23],... 

Similarity of reaction between cyclic and acyclic compounds. 

Elimination of OH and R2N in acid conditions. Similarity of reactions of acyclic and cyclic cornpounds. ... 

Due to a similarity of reaction stages in the Lotka and Lotka-Volterra models the equations for the pop and pop remain the same as in Section 8.2. Other kinetic equations are slightly simplified, a number and multiplicity of integrals are reduced. 

A comparable study of bromine addition to steroidal A -derivatives with varied substitution at C(3> and/or C(x ) also revealed rate retardation by electronegative substituents [103], and an analysis of data by the Taft method [104] yielded a reaction constant in the range —2.0 to — 2.7f. Although the Hammett and Taft reaction constants ( and q ) are not strictly comparable, these values indicate a similarity of reaction mechanism between the two types of olefin. Since chlorination in saturated aliphatic systems is believed to involve chloronium ions rather than classical carbonium ions, we would expect chlorine addition to A -steroids to produce a -value not greatly different from bromination. This does not appear to have been studied. 

Satoh, H., Sacher, O., Nakata, T., Chen, L., Gasteiger, J. and Funatsu, K. (1998). Classification of Organic Reactions Similarity of Reactions Based on Changes in the Electronic Features of Oxygen Atoms at the Reaction Sites. J.Chem.Inf.Comput.ScL, 38,210-219. 

Density Domain Shape Similarity of Reaction Paths. 76... 

The above tools are also suitable for studying the similarity of reaction paths. Two reaction paths Pi and P2 are regarded shapewise equivalent within the above context (ID-shape equivalent) if and only if the numbers w, and W2 of their... 

In order to quantify a component by GC, it is possible to use the methods of either the internal or external standard. For the particular case of essential oils, one can frequently use the method of relative concentrations related to the total area of the peaks, due to the similarity of reaction factors that the main components of the terpene family have. What follows is a brief description of each one of them, its advantages and limitations. 

Because of the similarity of reactions of P450s 3A4 and 3A5, homology models based on P450 3A4 stractures are probably reasonably vaUd for P450 3A5. Relatively little site-directed mutagenesis of P450 3A5 has been done, but one study of note is the effort by Correia and Halp-ert to utilize the differences in reactions with af-latoxin Bj [1331, 1478] to probe the effects of changing residues in the active site [1406]. 

The similarity of reaction rates and yields conld be explained by either interconversion of these species to one another, or conversion of each of them to a more advanced, common reactive intermediate. H-NMR analysis of a mixture of TBAF with either siletane 13, silanol 32, disiloxane 202, or fluorosilane 203 shows only two species that are formed almost immediately. One is identified as the disiloxane of the corresponding silanol, and the other species an unknown compound 204 (or 205) containing both silicon and fluorine as determined by Si- and F-NMR (Scheme 7.51). Moreover, the ratio of204 (205) to disiloxane increased with TBAF stoichiometry under typical conditions for cross-coupling the ratio is heavily in favor (>10 1) of204 (205). 

Mechanisms of reactions with molecular oxygen are well understood because they have received considerable research investment. There exist similarities of reactions with molecular oxygen and reactions with carbon dioxide and steam (water vapor). Initially, it is irrelevant to discuss in some detail the carbon-molecular oxygen reaction, but, as is clarified later, this discussion also provides meaningful clues as to how carbon atoms are extracted in a gasification process by carbon dioxide or steam. 

Ay F, Kahveci T (2010) Functional similarities of reaction sets in metabohc pathways. In Proceedings of the first ACM international conference on bioinformatics and computational biology, ACM, Niagara Falls, New York, pp 102-111... 

This similarity of reaction times in tasks with equal numbers of task elements but different composition of stimuli and response has to be shown. 

Novel criteria that help to plan organic syntheses have been defined for the similarity of structures. Likewise, criteria that can be used to search reaction databases have been conceived for the similarity of reactions. 

Similarity searching in reaction databases has gained widespread interest since it became available (in REACCS and ORAC) about two years ago. The definition of similarity of reactions in these reaction retrieval systems is based on common substructural features in the reaction centres and in the reactants. Without doubt, these definitions of reaction similarity are of great usefulness. However, we wanted to broaden the discussion of reaction similarity and search for additional helpful ideas. To achieve this we took a totally different approach to specify the similarity of reactions. Our approach is based on the idea that chemists often want to know the exact conditions for running a reaction. We assumed that similar reactions should be those that proceed under similar reaction conditions. 

The definitions of the similarities of reactions, that are based on physicochemical parameters, give new tools for searching reaction databases. They allow us to draw inferences on the reaction conditions for a desired transformation. 

One of the oldest reports of a synthesis of a highly substituted 3-pyrrolin-2-one involved a type e cyclization. Bashour and Lindwall treated y-oxo-P-hydroxycarboxamide 205 with HCl and obtained a product presumed to be 5-hydroxy-3-pyrrolin-2-one 206 (Scheme 46 1935JA178). Given the similarity of reactions that have been reported since then (e.g.. Scheme 42), this probably was the correct structural assignment. Moon later reported a synthesis of 4-acyl-3-pyrrolin-2-ones via thermal cyclization of y-ketocar-boxamides (1977JOC2219). 

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