Basicity Bond path

Under equilibrium conditions (thermodynamic control), the allylic source adds to the polarized multiple bond (path AdN). However, the allylic source can also serve as a base and may deprotonate the sink, creating a mixture of sources and sinks and thus a messy statistical mixture of products. Clean products result if the source is just the deprotonated sink or if the sink has no acidic protons. With ketones, the equilibrium of the attack step favors the starting materials, and therefore the reaction goes to completion only if driven by a following elimination. In the next Adisj2 example, the source is the deprotonated sink. The product is an aldehyde-alcohol, or aldol, a name now used for the general process of an enol (acidic media) or enolate (basic) reacting with an aldehyde or ketone. 

Although AILs (bond paths) in AIM theory often coincide with our basic understanding of what a chemical bond is, this is not always the case. There has been a lot of debate on this topic in the literature, with the main source of disagreement arising from insufficient distinction between the AIM concept and our... 

A radically new stage of development of lateral models is related to the application of PT methodology. The term percolation was introduced by Broadbent and Hammersley [225] to describe the new class of mathematical problems connected to the analysis of infiltration of liquids or the path of an electrical current through a labyrinth of bonded and nonbonded elements. This theory has become very fashionable in various fields of physics, chemistry, and technical applications (e.g., a problem of displacement of oil from a porous medium [8,223,226,227]). The basics of this theory has been comprehensively discussed in several reviews [121,228-232] and monographs [8,233,234],... 

Since the second solvent pair fall within the poor hydrogen bonding group of solvents, increased basicity of the organic base in these solvents would be consistent with the observed behavior. Based on the model compound studies, indications are that the base-catalyzed imidization process may involve a two-step mechanism, Jee Scheme 23. The first step corresponds to the complete or partial proton abstraction from the amide group with the formation of an iminolate anion. Since this iminolate anion has two possible tautomers, the reaction can proceed in a split reaction path to either an isoimide- or imide-type intermediate. Although isoimide model reactions indicate an extremely fast isomerization to the imide under the conditions employed for base-catalysis, all indications to date are that it is not an intermediate in the base-catalyzed imidization of amic alkyl esters. 

A second basic interaction pathway between transition metal complexes and organic substrates is SET (Path B). The overall processes can involve one individual or several sequential SET steps. For the latter, timing and direction of SET steps determine the reaction outcome significantly. The catalyzed reaction can proceed either as redox-neutral processes, in which oxidative and reductive SET steps are involved in the catalytic cycle, or as overall oxidative or reductive catalytic reactions, where two oxidative or reductive SET steps occur consecutively in the catalytic cycle. The third pathway (Path C) consists of a direct atom or group abstraction by the metal complex, which is possible for a weak R-X bond. 

This list of examples in which small perturbations of the chemical composition of the electrolyte qualitatively changed the nonlinear dynamics demonstrates how intricate the repercussion of interfacial reaction steps on temporal motions can be. It is likely that in all of the mentioned systems the basic instability is the same and can be understood in terms of the interaction of (a) surface poisoning by the indirect path (b) replenishing of the surface by the reaction between CO and surface bonded... 

In the last few years, the polarizable continuum model for the study of solvation has been extended to consider multideterminantal wavefunctions. Such novel techniques allow the study of the most important solvent effects on chemical reactions. In this context, the valence bond theory provides a way to analyze such effects through the transcription of the, generally, complicated multiconfigurational wavefunctions into sums of few selected classical structures, which are, in fact, more useful to understand the electron distribution rearrangement along a reaction path. In this chapter, the valence bond analysis of CASSCF wavefunctions calculated for chemical reactions in solution is discussed in details. By way of example, the results for some basic chemical processes are also reported. 

In path A, the electrons on the negative oxygen reform the double bond as hydride leaves. Hydride is too basic to leave by itself, so it is transferred to the electrophilic carbonyl carbon of another aldehyde molecule in a concerted step. This step is relatively slow and occurs only when no other reaction pathways, such as an aldol condensation, are available. 

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