Reactivity principle

I believe that, for those who seek to discover new reactions, the most insightful lessons come from trying to trace important reactivity principles back to their origins. ... 

Molecular Size and Chemical Reactivity Principles of Condensation Polymerization... 

Sometimes, the action of PCC on alcohols leads to products that can be explained by complex mechanism, in which several of the reactivity principles mentioned above act in a sequential manner.334... 

Trimethylsilyl compounds with electron-withdrawing substituents (CN, I, Cl, Br, N, NCO, CNO, etc.) have been used in syntheses based on the hard-soft reactivity principle, with the silicon atom having electropositive and the substituent electronegative character. The bond between the pseudo-halide trifluoromclhyl and the trimethylsilyl center should also polarize with the trifluoromclhyl group bearing substantial negative charge.23-24... 

These considerations form the basis for the numerous techniques that are now available for the chemical modification of proteins. The sections that follow will examine these techniques and the reactive principles by which they function. A section describing reactions that display orthogonal reactivity to native protein functional groups has also been included because of the growing importance of these reactions as tools to label proteins in complex mixtures. Because it is not practical to summarize all protein bioconjugation methods here, this information instead is intended to serve as an introduction to the concepts that drive the development of these reactions. Several additional reviews and books on protein modification have been listed in the Further Reading section. 

The other example is, of course, DNA. In retrospect, it seems clear that there was hardly any other comparably fundamental reactivity principle on the territory of natural products chemistry waiting to be discovered than that we know today as Watson-Crick basepairing. 

We anticipate that this monograph will be of value to both expert and novice practitioners in the area of metal-catalyzed cross-coupling reactions. We hope that it will fiirther stimulate both the development and applications of this enormously useful and already widely employed reactivity principle in all fields of chemistry involving synthesis depending upon carbon-carbon bond formation. 

The previous review on this subject was published in 1966. Though the number of reagents and systems investigated has been greatly expanded since that time, this review is structured after the Lyle and Anderson document. Some of the earlier observations regarding general reactivity principles deserve restatement. 

Associated with these properties, important chemical reactivity principles have been rationalized within the framework of conceptual DFT the hard and soft acids and bases principle (F1SAB) [9], the Sanderson electronegativity equalization principle (EEP) [11], the maximum hardness principle (MF1P) [9,12,13], and the minimum polarizability principle (MPP) [14], The aim of this chapter is to revise the validity of the last two principles in nontotally symmetric vibrations. We start with a short section on the fundamental aspects of the MF1P and MPP (section 2). Section 3 focuses on the breakdown of these principles for nontotally symmetric vibrations, while section 4 analyses the relationship between the failure of the MF1P and the pseudo-Jahn-Teller (PJT) effect. A mathematical procedure that helps to determine the nontotally symmetric distortions of a given molecule that produce the maximum failures of the MPP or the... 

Although the equal reactivity principle can be used as a guide for the rate of reaction of accessible groups, reactions with solid polymers may be hindered or enchanced by the presence of neighboring group (37). This is the case in the hostile interaction of methanol and ethanol on the SMA copolymer where the anhydride group appears to react with the lower alcohols to form half acid/ester. 

Metal-H2 coordination and activation toward OA convey a rate elegance in chemistry, and most of the structure, bonding, and reactivity principles derived from H-H bond activation should apply to all types of metal bond interactions. The major points discussed above and in the rest of this book are summarized here in terms of H2 activation ... 

Addition reactions contain the largest synthetic potential in fullerene chemistry but they can also be used as a probe for screening the chemical properties of fullerene surfaces. Analysis of the nature of addition reactions, of geometric and electronic structures of educts and products allows one to deduce reactivity principles which are the central subject of this article. One striking conclusion is the following the fullerenes drew attention to a mostly overlooked chemistry criterion - the shape dependence of reactivity. This contribution focuses on the reactivity principles of Cgg as the most important and most intensively investigated fullerene. The addition chemistry of the higher fullerenes follows similar principles. 

Reactivity principles of Cgg which were deduced in preceding reviews [3,5] are still valid. However, the progress in the field of fullerene chemistry continuously increases our knowledge and allows us to refine the rules for the reactivity of this spherical carbon cluster. Based on the present state-of-the-art the following principles of Cgo chemistry are summarized. 

Mono-functionalization of C70 affords an isomeric product mixture in many cases. In accordance with the above reactivity principles, the main product usually results from attack of the reagent in the polar region at the most curved bond C(l)-C(2) (type a) followed by addition to the second most curved C(5)-C(6) bond (type/I) [27] (Figs. 4,5). 

E iles with vinylidene fluoride (VFz) copolymers in solution and have determined some reactivity principles which can be used to interpret the vulcanization behavior of related fluoco-elastomers. 

Flory has shown from empirical data that for a homologous series the velocity constant measured under comparable conditions approaches an asymptotic limit as the chain length increases. He therefore proposed the equal reactivity principle, which states in essence that the intrinsic reactivity of all functional groups is constant, independent of the molecular size. This principle is in apparent contradiction to the theoretical prediction of low chemical reactivity for macromolecules discussed above. Flory used the following arguments to explain the equality of reactivity between macromolecules and their low-molecular-weight analogs. 

Flory s equal reactivity principle, which has been validated on mechanistic and experimental grounds, has greatly simplified an otherwise complicated kinetic analysis of condensation polymerization. This... 

Chemical Reactivity Principles Hierarchy According to the Biological Activity of... 

The working ligand progress curve (10) directly depends on recorded and computed activity, which in turn depend on the chemical reactivity indices considered, employing what can be called quantitative reactivity-activity relationships (QRAR). For each DFT framework and each reactivity index, a different progress curve for a given ligand-receptor interaction is obtained. The immediate inference can be made that faster consumption of L(f) is involved for the more reactive index, and therefore, a more preeminent reactivity principle is associated. This allows the researcher... 

Fig. 1 The workflow of structure-activity relationships involving conceptual and computational density functional theory through molecular frontier information (e.g., HOMO and LUMO), which are primarily employed as electronegativity (x) and chemical hardness (rf) indices and are then combined to form chemical power (x/2 y) and electrophilicity (x l2rj) reactivity measures. These values are correlated with observed biological and ecological activity (A) to provide the QSAR models (A ) to finally produce ligand progress curves (L) that provide a hierarchy of chemical reactivity principles involved in biological activity within a given DFT computational framework and species of interest...

In order to form a more intuitive (although not complete) idea of how the above-nominated reactivity principles act at the energetic level. Fig. 2 depicts the equality and inequality variants in the left (a) and right (b) parts, respectively. In Fig. 2a, there is a clear difference during a reaction or bonding process in the electronegativities of the partners first encountered the main effect of reactivity will be the... 

---