Organic chemistry electrophile

Background Needed for this Chapter References to Clayden, Organic Chemistry Electrophilic aromatic substitution chapter 22. (Electrophilic Aromatic Substitution) Nucleophilic aromatic substitution chapter 23 (Electrophilic Alkenes). 

Nitration is important for two reasons firstly, because it is the most general process for the preparation of aromatic nitro compounds secondly, because of the part which it has played in the development of theoretical organic chemistry. It is of interest because of its own characteristics as an electrophilic substitution. 

Carey Organic Chemistry I 12 Reactions of Arenes Fifth Edition Electrophilic Aromatic... 

Ionic Inflate derivatives of nonmetallic elements such as selenium, sulfur, phosphorus, and iodine form an important class of reagents lor organic chemistry. Highly electrophilic phenylselenyl triflate can be used in the cyclization of 5- and 6-hydroxyalkenes, affording the corresponding tetrahydrofurans and pyrans [132] (equation 68). 

We call this reaction electrophilic aromatic substitution it is one of the fundfflnental processes of organic chemistry. 

When a Br nsted base functions catalytically by sharing an electron pair with a proton, it is acting as a general base catalyst, but when it shares the electron with an atom other than the proton it is (by definition) acting as a nucleophile. This other atom (electrophilic site) is usually carbon, but in organic chemistry it might also be, for example, phosphorus or silicon, whereas in inorganic chemistry it could be the central metal ion in a coordination complex. Here we consider nucleophilic reactions at unsaturated carbon, primarily at carbonyl carbon. Nucleophilic reactions of carboxylic acid derivatives have been well studied. These acyl transfer reactions can be represented by... 

The classical age of preparative organic chemistry saw the exploration of the extensive field of five-membered heterocyclic aromatic systems. The stability of these systems, in contrast to saturated systems, is not necessarily affected by the accumulation of neighboring heteroatoms. In the series pyrrole, pyrazole, triazole, and tetrazole an increasing stability is observed in the presence of electrophiles and oxidants, and a natural next step was to attempt the synthesis of pentazole (1). However, pentazole has eluded the manifold and continual efforts to synthesize and isolate it. 

The palladium component may be added to the reaction mixture as Pd(0)- as well as Pd(II)- compound in the latter case the Pd(II)- first has to be reduced to Pd(0)- by excess stannane. Since the first publication on this coupling method by Stille in 1978, this reaction has gained increased importance in synthetic organic chemistry. This is due to the fact that many different types of substrates can be used in this reaction. The following table lists possible carbon electrophiles and stannanes that can be coupled in any combination. 

The Lead-Off Reaction Addition of HBr to Alkenes Students usually attach great-importance to a text s lead-off reaction because it is the first reaction they see and is discussed in such detail. 1 use the addition of HBr to an alkene as the lead-off to illustrate general principles of organic chemistry for several reasons the reaction is relatively straightforward it involves a common but important functional group no prior knowledge of stereochemistry or kinetics in needed to understand it and, most important, it is a polar reaction. As such, 1 believe that electrophilic addition reactions represent a much more useful and realistic introduction to functional-group chemistry than a lead-off such as radical alkane chlorination. 

E. Berliner, Progress in Physical Organic Chemistry, Vol. 2, Wiley, New York. 1964, p. 258. R. O. C. Norman and R. Taylor, Electrophilic Substitution in benzenoid Compounds, Elsevier, Amsterdam, 1965, p. 26. 

Ninety-five percent of the reactions that we see in organic chemistry occur between a nucleophile and an electrophile. A nucleophile is a compound that either is negatively charged or has a region of high electron density (like a lone pair or a double bond). An electrophile is a compound that either is positively charged or has a region of low electron density. When a nucleophile encounters an electrophile, a reaction can occur. 

The oxidation of C-H bonds represents one of the major challenges in organic chemistry. C-H bond oxidations are often performed in strongly acidic media (such as oleum) in order to enhance the electrophilicity of the metal centre. This indeed requires catalysts that are stable under very challenging conditions. 

The electrophilic bromination of ethylenic compounds, a reaction familiar to all chemists, is part of the basic knowledge of organic chemistry and is therefore included in every chemical textbook. It is still nowadays presented as a simple two-step, trans-addition involving the famous bromonium ion as the key intermediate. T]nis mechanism was postulated as early as the 1930s by Bartlett and Tarbell (1936) from the kinetics of bromination of trans-stilbene in methanol and by Roberts and Kimball (1937) from stereochemical results on cis- and trans-2-butene bromination. According to their scheme (Scheme 1), bromo-derivatives useful as intermediates in organic synthesis... 

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