Electron-deficient sites/species

A nucleophile is a species that attacks electron-deficient sites and donates a lone pair of electrons to form a covalent bond. Halogenoalkanes get more reactive as the C-X bond gets longer and therefore weaker. Iodoalkanes therefore react fastest and fluoroalkanes slowest. 

In summary, the results of this investigation indicated that the formal oxidation of the nickel sites in a composite nickel-iron oxyhydroxide modifies the electronic and structural properties of the ferric sites yielding a more d-electron deficient iron species. Although it may be reasonable to suggest that the elec-trocatalytic activity of this composite oxide for oxygen evolution may be related to the presence of such highly oxidized iron sites,... 

Two types of interactions have been shown to be involved in superelectrophilic species. Superelectrophiles can be formed by the further interaction of a conventional cationic electrophile with Brpnsted or Lewis acids (eq 16).23 Such is the case with the further protonation (protosolvation) or Lewis acid coordination of suitable substitutents at the electron deficient site, as for example in carboxonium cations. The other involves further protonation or complexation formation of a second proximal onium ion site, which results in superelectrophilic activation (eq 17).24... 

Ketones and nitriles are rather soft bases their coordination onto electron-deficient sites on oxides is, therefore, relatively weak. One may, however, expect an improved specificity of chemisorption due to their softness. Unfortunately, however, these substances very easily undergo chemical transformations at oxide surfaces. Thus, carboxylate structures are formed on adsorption of acetone on alumina (194, 245-247), titanium dioxide (194), and magnesium oxide (219, 248, 249). Besides, acetone is also coordinated onto Lewis acid sites. A surface enolate species has been suggested as an intermediate of the carboxylate formation (248, 249). However, hexafluoroacetone also leads to the formation of trifluoroacetate ions (219). The attack of a basic surface OH ion may, therefore, be envisaged as an alternative or competing reaction path ... 

A carbcne presents some similarities with a carbenium ion, since both are elec-tron-deficient species. This explains the fact that both are prone to rearrangement reactions doublets migrate towards the electron-deficient sites and groups linked to the migrating doublet are thus transfered from different positions of a molecule. 

Diastereoisomers stereoisomers that are not enantiomers Electrophilic reaction a reaction in which an electron-rich species is attacked by an electron deficient site of another reagent to form a new covalent bond Enantiomers molecules whose structures are nonsuperim-posable mirror images of each other... 

Nucleophiles are electron-rich species that can form a covalent bond by donating two electrons to an electron-deficient site. Nucleophiles are negatively charged (anions) or neutral molecules that contain a lone pair of electrons. 

In additional experiments it has been shown that iron is interacting with platinum, i.e., it is located in atomic closeness to Pt. In the bimetallic nanocluster, due to the high electropositivity of iron, there is an electron transfer from iron to platinum. The net result is the formation of electron deficient iron species at the Pt surface. The authors suggested that these electron-deficient or low-valent iron species on the Pt surface might act as Lewis acid adsorption sites. These sites, due... 

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