Electrophilic interactions

Reactivity and orientation in electrophilic aromatic substitution can also be related to the concept of hardness (see Section 1.2.3). Ionization potential is a major factor in determining hardness and is also intimately related to the process of (x-complex formation when an electrophile interacts with the n HOMO to form a new a bond. In MO terms, hardness is related to the gap between the LUMO and HOMO, t] = (sujmo %omo)/2- Thus, the harder a reactant ring system is, the more difficult it is for an electrophile to complete rr-bond formation. 

Feste, A. S. and Khan, I., Separation of glucooligosaccharides and polysaccharide hydrolysates by gradient elution electrophilic interaction chromatography with pulsed amperometric detection, /. Chromatogr., 630,129, 1993. 

The macroscopic property of interest, e.g., heat of vaporization, is represented in terms of some subset of the computed quantities on the right side of Eq. (3.7). The latter are measures of various aspects of a molecule s interactive behavior, with all but surface area being defined in terms of the electrostatic potential computed on the molecular surface. Vs max and Fs min, the most positive and most negative values of V(r) on the surface, are site-specific they indicate the tendencies and most favorable locations for nucleophilic and electrophilic interactions. In contrast, II, a ot and v are statistically-based global quantities, which are defined in terms of the entire molecular surface. II is a measure of local polarity, °fot indicates the degree of variability of the potential on the surface, and v is a measure of the electrostatic balance between the positive and negative regions of V(r) (Murray et al. 1994 Murray and Politzer 1994). 

Weak nucleophile-electrophile interactions (and the donor-acceptor complexes) are considered precursors in aromatic electrophilic substitutions133 and in additions of electrophiles to C=C double bond of olefins the first step (the addition of the electrophile to an electron-rich substrate) is probably the same for both reactions. 

Electrophilic attack, metal ions, 34 266-270 Electrophilic interactions, metal ions, 34 284 Electroreflning, of actinide metals, 31 13, 15, 17, 20, 21... 

Reaction with Electrophiles, including Oxidizing Agents 5.13.3.3.1 Electrophilic interactions at the ring oxygen atom... 

Some striking demonstrations of metal-metal bond lability are provided by cluster rearrangements due to protonation. This is the case for some anionic osmium clusters (cf. Section VI). It involves ligand activation for some tetrairon clusters (51-53). Thus, the clusters 9 and 11 open up upon protonation, and compensation for the lost iron - iron bonds in the products 10 and 12 comes from the bonding between one iron atom and a carbonyl oxygen. The relation of these unusual nucleophile-electrophile interactions to cluster-induced CO transformations is obvious. 

Deprotonation reactions if the 2-benzopyrylium cation has an a-alkyl substituent or a group with a mobile hydrogen atom in any other fragment of the molecule. This conversion takes place over a wide range of conditions, and it often accompanies nucleophilic additions. Moreover, the problem of the acid-base and nucleophilic-electrophilic interactions for 2-benzopyrylium salts concerns not only the primary step of their reactions with nucleophiles, but also the ring-open forms, as shown in Section III,C,4. 

Stereoselective vicinal diamination of dihydropyridines 309 by electrophilic interaction with iodine in the presence of secondary amines leading to tetrahydropyrimidines 312 is described in [338, 339] (Scheme 3.107). The... 

Compounds representing a non reversible mode of action. Electrophilic interactions involve substitution or conjugation of electron-rich groups to nucleophilic sites in cellular macromolecules. Volume 1(8). 

To characterize the global readiness of molecules to donate or accept electron charge, the lowest ionization potential and greatest electron affinity (that are often simply called ionization potential and electron affinity) would be the best parameters when referring to Equation 6.37 and Equation 6.40 as (highly simplified) model reactions for nucleophilic and electrophilic interactions of a compound with endogenous reaction partners, and the associated MO energy values ... 

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