Nucleophilic aromatic substitution leaving groups

Indeed the order of leaving group reactivity m nucleophilic aromatic substitution is the... 

The generally accepted mechanism for nucleophilic aromatic substitution m nitro substituted aryl halides illustrated for the reaction of p fluoromtrobenzene with sodium methoxide is outlined m Figure 23 3 It is a two step addition-elimination mechanism, m which addition of the nucleophile to the aryl halide is followed by elimination of the halide leaving group Figure 23 4 shows the structure of the key intermediate The mech anism is consistent with the following experimental observations... 

Nucleophilic aromatic substitution by the elimination-addition mecha nism can lead to substitution on the same carbon that bore the leaving group or on an adjacent carbon... 

Cycloalkene (Section 5 1) A cyclic hydrocarbon characterized by a double bond between two of the nng carbons Cycloalkyne (Section 9 4) A cyclic hydrocarbon characterized by a tnple bond between two of the nng carbons Cyclohexadienyl anion (Section 23 6) The key intermediate in nucleophilic aromatic substitution by the addition-elimination mechanism It is represented by the general structure shown where Y is the nucleophile and X is the leaving group... 

Nucleophilic aromatic substitution (Chapter 23) A reaction m which a nucleophile replaces a leaving group as a sub stituent on an aromatic nng Substitution may proceed by an addition-elimination mechanism or an elimination-addition mechanism... 

A variation of the aromatic nucleophilic substitution process in which the leaving group is part of the entering nucleophile has been developed and is called vicarious nucleophilic aromatic substitution. 

Fluonde Ion as Nucleophile and a Leaving Group in Aromatic Nucleophilic Substitution Reactions Vlasov V M J Fluorine Chem 6i. 193-216 77... 

The reaction of benzenesulfonic acid with sodium hydroxide (first entry in Table 24.3) proceeds by the addition-elimination mechanism of nucleophilic aromatic substitution (Section 23.6). Hydroxide replaces sulfite ion (S03 ) at the carbon atom that bear s the leaving group. Thus, p-toluenesulfonic acid is converted exclusively to p-cresol by an analogous reaction ... 

Cyclohexadienyl anion (Section 23.6) The key intermediate in nucleophilic aromatic substitution by the addition-elimination mechanism. It is represented by the general structure shown, where Y is the nucleophile and X is the leaving group. 

Nucleophilic aromatic substitution occurs only if the aromatic ring has an electron-withdrawing substituent in a position ortho or para to the leaving group. The more such substituents there are, the faster the reaction. As shown in Figure 16.18, only ortho and para electron-withdrawing substituents stabilize the anion intermediate through resonance a meta substituent offers no such resonance stabilization. Thus, p-ch oronitrobenzene and o-chloronitrobenzene react with hydroxide ion at 130 °C to yield substitution products, but m-chloronitrobenzene is inert to OH-. 

In general, the more nitro groups present on the aromatic ring the easier the leaving group displacement. Nucleophilic aromatic substitution is therefore a very important reaction in the chemistry of polynitroarylenes. While the use of such reactions has been extensive in the synthesis of explosives, the reaction also has important implications for the chemical stability of many polynitroarylenes (discussed in Section 4.8.2). 

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