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Electron-rich molecule

In turn, 1O2 is a very electrophilic excited state species of molecular oxygen that interacts efficiently with electron-rich molecules, such as aminoadd residues of proteins like histidine, metionine, tryptophan, tyrosine, etc., by both physical and chemical quenching processes, eqns. 9 and 10 (Davies, 2003 Bisby et al., 1999). [Pg.12]

Heterolytic catalysis is promoted by W6+, Ti4+, Cr3+, V5+, and many Mo6+ complexes. These complexes do not normally react with peroxides. However, in the presence of electron-rich molecules, such as alkenes, amines, sulfides, etc., oxygen insertion in the reactant occurs. For example,... [Pg.80]

When the nucleophile is an electron-rich molecule, RC60+ can be reduced via single electron transfer, producing a dimer (47). Thus, electrophilic aromatic substitution normally occurs with substituted benzenes (Figure 22, [A]), but the mode of the reaction is switched if the benzene is strongly activated (Figure 22, [B]). [Pg.263]

Vol. 30 R.D. Harcourt, Qualitative Valence-Bond Descriptions of Electron-Rich Molecules Pauling 3-Electron Bonds and Increased-Valence Theory. X, 260 pages. 1982. [Pg.422]

Basically, most reactions involve electron-rich molecules forming bonds to electron deficient molecules (i.e. nucleophiles forming bonds to electrophiles). The bond will be formed particularly between the nucleophilic centre of the nucleophile and the electrophilic centre of the electrophile. [Pg.77]

Both A1 and B are in Group 3 of the periodic table and have three valence electrons in their outer shell. These elements can form three bonds. However, there is still room for a fourth bond. For example in BF3, boron is surrounded by six electrons (three bonds containing two electrons each). However, boron s valence shell can accommodate eight electrons and so a fourth bond is possible if the fourth group can provide both electrons for the new bond. Since both boron and aluminium are in Group 3 of the periodic table, they are electropositive and will react with electron-rich molecules so as to obtain this fourth bond. Many transition metal compounds can also act like Lewis acids (e.g. TiCl4 and SnCl4). [Pg.101]

Nucleophiles Majority of organic reaction between a molecule that is rich in electrons and a molecule that is deficient in electrons. Such a reaction involves the formation of a new bond in which the electrons are provided by the electron-rich molecule. Electron-rich molecules are known as nucleophiles (meaningnucleus-loving). The easiest nucleophiles to identify are negatively charged ions with lone pairs of electrons (e.g., the hydroxide ion), but neutral molecules can also act as nucleophiles if they contain electron-rich functional groups (e.g., an amine). [Pg.266]

R. D. Harcourt, Qualitative Valence Bond Descriptions of Electron-Rich Molecules... [Pg.416]

As a tribute to Pauling s contributions, I shall restate and summarize some of the implications for bonding theory that arise when the three-electron bond is incorporated as a mainstream component for VB descriptions of the electronic structures of electron-rich molecules. Attention will be focussed on increased-valence structures for molecular systems that involve four-electron three-centre and six-electron four-centre bonding units. However initially, consideration will be given to the one-electron bond, for which Pauling also provided some attention to both the theory and examples of systems that involve this type of bond in their VB structures. As indicated in ref. [8(a)], experimentally one-electron bonds and three-electron bonds are abundant and well-characterized for odd-electron systems. [Pg.450]

Paramagnetic electron-rich molecules and molecular ions that involve atoms of main-group elements... [Pg.456]

Specific Insertion of 0=C=S into the N-Si Bond of an Extremely Electron-rich Molecule as Evident from the X-Ray Crystal Structure... [Pg.141]

The LE model is a simple but very successful model, and the rules we have used for Lewis structures apply to most molecules. To implement this model we have relied heavily on the octet rule. So far we have treated molecules for which this rule is easily applied. However, inevitably, cases arise where the importance of an octet of electrons is called into question. Boron, for example, tends to form compounds in which the boron atom has fewer than eight electrons around it—it does not have a complete octet. Boron trifluoride (BF3), a gas at normal temperatures and pressures, reacts very energetically with molecules such as water and ammonia that have available lone pairs. The violent reactivity of BF3 with electron-rich molecules occurs because the boron atom is electron-deficient. Boron trifluoride has 24 valence electrons. The Lewis structure that seems most consistent with the properties of BF3 is... [Pg.617]


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See also in sourсe #XX -- [ Pg.403 ]




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