Electron electrophilic

Nucleophiles have an electron-rich site, either because they are negatively charged or because they have a functional group containing an atom that has a lone pair of electrons. Electrophiles have an electron-poor site, either because they are positively charged or because they have a functional group containing an atom that is positively polarized. 

In the bent mode of bonding, the nitrosyl N has approximately sp2 hybridization with a lone pair of electrons. Electrophiles that have been reported to attack at this position include 02 (192, 214, 215), H+ (190, 205), and NO (193). The first of these reacts with nitrosyl to give nitro and nitrato species, depending on the particular complex system in question. In a study of the... 

In a quantitative theory we shall also have to calculate the energy difference between the normal state and the activated state in which on the reacting atom is localized either a pair of electrons (electrophilic reaction SE), a sextet (pos. charge, nucleophilic reaction SN), or a single electron (radical reaction SR) or in which a pair of electrons is localized in a certain bond (true double bond reactions). The remaining possibilities for resonance will determine mainly which of the possible activated states will have the lowest energy and thus what course the reaction will take (localization hypotheses). 

In tt-bond electrophiles, the electrophilic atom E has an octet, but it is attached by a 77 bond to an atom or group of atoms that can accept a pair of electrons. Electrophiles of the 77-bond type commonly have C=0, C=N, or C=N bonds, in which the less electronegative atom is the electrophilic one. C=C and C=C bonds are electrophilic if they are attached to electrophilic atoms (see below). Miscellaneous 77-bond electrophiles include SO3 and RN=0. Certain cationic electrophiles can be classified as either the Lewis acid type or the 77-bond type depending on whether the best or second-best resonance description is used (e.g., R2C=OH <-> R2C-OH also, H2C=NMe2, RC O, 0=N=0, NsO). When a nucleophile attacks a 77-bond electrophile, the 77 bond breaks, and the electrons move to the other atom of the 77 bond, whose formal charge is decreased by 1. 

In contrast, electrophilic reagents are the opposite of nucleophilic ones. They are often positively charged, or at least are electron poor by virtue of having an empty orbital, i.e. an atomic orbital in which there are no electrons. Electrophiles generally attack centres of high electron density, such as double bonds. 

We have shown that the intrinsic electronic contribution to the Hammett substituent constant, cre(o>), may be obtained from a statistical analysis that follows from the comparison of the experimental <7p values and the electronic electrophilicity index co evaluated for isolated molecules.127 The analysis was performed for the electrophilicity of a series of substituted ethylenes, X-CH=CH2, and the crp values reported by Hansch et al.12S for a wide list of functional groups (FG), X-, commonly present in organic compounds. 

Organic reactions usually occur at sites within molecules where there is a special availability or deficiency of electrons. Electrophiles are regions of a molecule or ion that are positive or deficient in electrons and which tend to attract electron-rich species and accept electrons in a chemical reaction. Nucleophiles are electron-rich, provide electrons in a chemical reaction, and tend to attract electron-deficient or positive species. 

Molecular electrostatic potential The molecular electrostatic potential (MEP) associated with a molecule arises from the distribution of electrical charges of the nuclei and electrons of a molecule. The MEP is quantum mechanically defined in terms of the spatial coordinates of the charges on the nuclei and the electronic density function p(r) of the molecule. As the MEP is the net result of the opposing effects of the nuclei and the electrons, electrophiles will be guided to the regions of a molecule where the MEP is most negative. The MEP is a useful quantity in the study of molecular recognition processes. 

An electrophile has an electron-deficient atom that is capable of accepting a pair of electrons. Electrophilic centers include atoms that are electron deficient due to inductive effects, as well as carbocations, which have an empty p orbital. 

These tt bond electrons will tend to react with substances deficient in electrons, i.e. agents attracted to electrons (electrophilic agents, acids), by the process of electrophilic addition. 

Electrophilic hydroxymethylation of ortho to the phenolic group is catalyzed by protic acids. In the next step, both hydroxy groups are protected as acetonide, cyclic ketal, and then the dimsyl anion reacts with the C=0 group as a six-electron electrophile forming epoxide. In the final steps, regioselective opening of epoxide... 

In general, the compounds of the Group 4 metals, such as halides and alkoxides, are well known as Lewis acids to catalyze two-electron electrophilic reactions, and their metallocenes coupled with alkylation and/or reduction agents were effective catalysts for the coordination polymerization of olefins. For the transition metal-catalyzed radical polymerization, their alkoxides, such as Ti(Oi-Pr)4, have also been employed as an additive for a better control of the products. Contrary to the common belief that the Group 4 metals rarely undergo a one-electron redox reaction under mild conditions, there have been some reports on the controlled radical polymerization catalyzed or mediated by titanium complexes, although the conflict in the mechanism between the (reverse) ATRP and OMRP is also the case with the Group 4 metal complexes. 

So far we have considered only the effect of reaction energy and of the electronic electrophilicity parameter on chemical reactivity. ISM implies that other structural factors, such as force constants and bond lengths, can also play a significant role. Although this may be found in very specific cases, it does not have the generality of the factors previously discussed. 

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