Addition-elimination mechanism nucleophilic aromatic substitution

Mechanism 17-7 Nucleophilic Aromatic Substitution (Addition-Elimination) 787... [Pg.17]

Mechanism of nucleophilic aromatic substitution by elimination addition (the benzyne mechanism). [Pg.707]

The Addition-Elimination Mechanism of Nucleophilic Aromatic Substitution... [Pg.977]

THE ADDITION-ELIMINATION MECHANISM OF NUCLEOPHILIC AROMATIC SUBSTITUTION... [Pg.977]

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... [Pg.977]

Section 23 6 Nucleophilic aromatic substitutions of the type just shown follow an addition—elimination mechanism... [Pg.987]

Other aryl halides that give stabilized anions can undergo nucleophilic aromatic substitution by the addition-elimination mechanism Two exam pies are hexafluorobenzene and 2 chloropyridme... [Pg.987]

Nucleophilic aromatic substitution can also occur by an elimination-addition mechanism This pathway is followed when the nucleophile is an exceptionally strong base such as amide ion m the form of sodium amide (NaNH2) or potassium amide (KNH2) Benzyne and related arynes are intermediates m nucleophilic aromatic substitutions that pro ceed by the elimination-addition mechanism... [Pg.987]

The product of this reaction as its sodium salt is called a Meisenheimer complex after the Ger man chemist Jacob Meisenheimer who reported on their formation and reactions in 1902 A Meisenheimer complex corresponds to the product of the nucleophilic addition stage in the addition-elimination mechanism for nucleophilic aromatic substitution... [Pg.991]

Addition-elimination mechanism (Section 23 6) Two stage mechanism for nucleophilic aromatic substitution In the addition stage the nucleophile adds to the carbon that bears... [Pg.1274]

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... [Pg.1280]

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... [Pg.1289]

Nucleophilic Aromatic Substitution by the Addition-Elimination Mechanism... [Pg.589]

There are several mechanisms by which net nucleophilic aromatic substitution can occur. In this section we will discuss the addition-elimination mechanism and the elimination-addition mechanism. Substitutions via organometallic intermediates and via aryl diazo-nium ions will be considered in Chapter 11 of Part B. [Pg.590]

The addition-elimination mechanism uses one of the vacant n orbitals for bonding interaction with the nucleophile. This permits addition of the nucleophile to the aromatic ring without displacement of any of the existing substituents. If attack occurs at a position occupied by a potential leaving group, net substitution can occur by a second step in which the leaving group is expelled. [Pg.590]

SECTION 10.5. NUCLEOPHILIC AROMATIC SUBSTITUTION BY THE ADDITION ELIMINATION MECHANISM... [Pg.591]

Kinetic studies have shown that the enolate and phosphorus nucleophiles all react at about the same rate. This suggests that the only step directly involving the nucleophile (step 2 of the propagation sequence) occurs at essentially the diffusion-controlled rate so that there is little selectivity among the individual nucleophiles. The synthetic potential of the reaction lies in the fact that other substituents which activate the halide to substitution are not required in this reaction, in contrast to aromatic nucleophilic substitution which proceeds by an addition-elimination mechanism (see Seetion 10.5). [Pg.731]

FIGURE 23.5 The elimination-addition mechanism of nucleophilic aromatic substitution. [Pg.983]

Although nucleophilic aromatic substitution by the elimination-addition mechanism is most commonly seen with very strong amide bases, it also occurs with bases such as hydroxide ion at high temperatures. A " C-labeling study revealed that hydrolysis of chlorobenzene proceeds by way of a benzyne intennediate. [Pg.985]

Nucleophilic aromatic substitution by the elimination-addition mechanism can lead to substitution on the same carbon that bore the leaving group or on an adjacent carbon. [Pg.987]

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 ... [Pg.1000]

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