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Effects of Activating Groups

TABLE 6.1 Relative Stabilization Energies (kJniDH) of Cyclohexadienyl Anions for Monosubstituted Benzenes [Pg.138]

Adapted with permission from Birch et al. [31]. (1980) American Chemical Society. [Pg.138]

A summary of ring activation would not be complete without mention of steric effects. Since nucleophilic attack occurs in a plane perpendicular to that of the aromatic ring, substitutions are not usually very sensitive to the bulk of orf/io-substituents. However, steric hindrance by an ortho-methyl substituent may be observed as the steric requirements of the nucleophile increase. Thus, the introduction of a 6-methyl group in l-chloro-2,4-dinitrobenzene causes rate decreases by factors of 14, 22, and 276 in reactions with methoxide, aniline, and piperidine, respectively. The first two figures are attributable to the electronic effect of the methyl substituent, but with piperidine, an additional steric effect is apparent [50]. [Pg.140]


You should review the chapters in your lecture textbook that deal with electrophilic aromatic substitution. Pay special attention to halogenation reactions and the effect of activating groups. [Pg.356]

The directing effect of activating groups has been studied less extensively during this period. Vilsmeier formylation of 2-alkyl-5-methoxy-thiophens at... [Pg.414]

The Pomeranz-Fritsch-Bobbitt cyclisation of activated amino-acetal 38 yielded the desired 4-hydroxyquinoline 39 in acceptable yield. The non-obvious regioselectivity of the cyclisation can be attributed to the overriding para-directing effect of alkoxy groups. ... [Pg.483]


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Activating group effects

Activating groups

Active groups

Group Activation

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