Electrophilic and Nucleophilic Reagents

Although the C in (/) has an unshared pair of electrons. (/) is electrophilic because the C has only six electrons. 

The lOH has unshared electrons and is a nucleophile. Because of the polar nature of the C—Br bond, 

C acts as an electrophilic site. The displacement of Br by OH is initiated by the nucleophile HQ . 

Problem 3.9 Indicate whether reactant (1) or (2) is the nucleophile or electrophile in the following reactions  

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The condensation of a thiazolium with an oxonol dye in a basic medium is another example of the combination of electrophilic and nucleophilic reagents (Scheme 55). With a nonopening ring, the obtained neutrodimethine cyanine is not mesosubstimted (68). 

The rhenium complex 7 has been shown to react with both electrophilic and nucleophilic reagents (24,25) ... 

The effect of metal basicity on the mode of reactivity of the metal-carbon bond in carbene complexes toward electrophilic and nucleophilic reagents was emphasized in Section II above. Reactivity studies of alkylidene ligands in d8 and d6 Ru, Os, and Ir complexes reinforce the notion that electrophilic additions to electron-rich compounds and nucleophilic additions to electron-deficient compounds are the expected patterns. Notable exceptions include addition of CO and CNR to the osmium methylene complex 47. These latter reactions can be interpreted in terms of non-innocent participation of the nitrosyl ligand. 

Both electrophilic and nucleophilic reagents are able to cleave the ring in cyclic germanium-carbon compounds due to the ring strain and the polarizability of the germanium-carbon bond, as illustrated in Figure 748,49. 

Equations 24.68 and 24.69 represent the response to electrophilic and nucleophilic reagents, respectively [8]. On the other hand, Equation 24.70 is a nonlinear Fukui function [51] and Equation 24.71 represents a radical Fukui function [8]. All these functions are computed by using different molecular Hamiltonians. 

The isolated-molecule method stems from the pioneering work of Wheland and Pauling (1935) on the orientation effects of substituents in benzene derivatives. It assumes that electrophilic and nucleophilic reagents attack preferentially at positions of high and low charge (qf) respectively, thus providing a more precise formulation of earlier... 

Three major topics of research which are based on phase transfer catalyzed reactions will be presented with examples. These refer to the synthesis of functional polymers containing functional groups (i.e., cyclic imino ethers) sensitive both to electrophilic and nucleophilic reagents a novel method for the preparation of regular, segmented, ABA triblock and (A-B)n alternating block copolymers, and the development of a novel class of main chain thermotropic liquid-crystalline polymers, i.e., polyethers. 

These compounds all contain both an electron source (Y ) and an electron sink (Z+). Furthermore, their aromaticity is significantly reduced by the non-uniform electron distribution. Hence they are highly reactive. The orientations of the reactions of these compounds with electrophilic and nucleophilic reagents are deducible from their canonical forms (see structures 12-14). 

This is because they divide the molecule into electrophilic and nucleophilic species, which can be more easily converted into the appropriate electrophilic and nucleophilic reagents for reconnection. The most useful heterolytic disconnections are... 

The reactions of the binuclear complexes (X)(Y)M2L2 with both electrophilic and nucleophilic reagents can be divided into two categories those in which the binuclear skeleton is retained and those in which two mononuclear products are formed. 

These authors studied the action of several electrophilic and nucleophilic reagents on unsubstituted 1,2-benzoisoselenazole and found that while electrophiles attack the benzene ring, nucleophiles either substitute the 3-position of the heterocycle or cleave the ring. Thus nitration and bromina-tion led to the formation of monosubstituted derivatives at the 5 and 7 position. Potassium amide, however, gave the 3-amino derivative (5) [Eq. (5)]. 

Dibismuthines are very labile they react readily with free radicals, electrophilic and nucleophilic reagents, which all cleave the Bi-Bi bond. Some dibismuthines are thermolabile tetramethyldibismuthine decomposes at 25°C quantitatively into trimethylbismuthine and bismuth metal. The half-life of this dibismuthine is approximately 6 h in a dilute benzene solution [82OM1408]. Tetraphenyldibismuthine [83CC507] and 2,2, 5,5 -tetramethyl-bibismole are stable up to 100°C [920M2743]. 

Fig. 4.20 Frontier orbital interactions for carbenes with electrophilic and nucleophilic reagents...

The representations of nucleophilic attack on formaldehyde as involving the carbonyl LUMO and electrophilic attack on ethene as involving the HOMO also make a prediction about the trajectory of the approach of the reagents. The highest LUMO density is on carbon and it is oriented somewhat away from the oxygen. On the other hand, the ethene HOMO is the tt orbital, which has maximum density at the midpoint above and below the molecular plane. Calculations of the preferred direction of attack of electrophilic and nucleophilic reagents are in accord with this representation, as shown below. ... 

The high reactivity of acetylenic ethers toward both electrophilic and nucleophilic reagents is determined by the highly polarized character of the triple bond due to the contribution of the resonance structure RO =C=C R. The carbon atom p to oxygen is the usual site of electrophilic attack, while the a-carbon is reactive toward nucleophiles (equation 49). 

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