Benzenamine Substituted benzenes

Claisen-Schmidt condensation, 720, 728 with methylamine, 673, 873 nitration, 467, 873 reductive amination, 881 with vinyllithium, 556 Benzenamine, 859. See also Aniline Benzene, 54, 399-406, 433 34 acidity of, 552, 577 Birch reduction of, 413-414 derivatives, nomenclature of, 406-408 electrophilic aromatic substitution in,... 

Aromatic nitration is the best way to introduce nitrogen-containing substituents into the benzene ring. The nitro group functions as a directing group in further substitutions (Chapter 16) and as a masked amino function (Section 16-5), as unraveled in benzenamines (anilines Section 22-10). 

Benzene rings bearing the groups -NH2 and -OH are strongly activated. For example, halogenations of benzenamine (aniline) and phenol not only take place in the absence of catalysts but also are difficult to stop at single substitution. The reactions proceed very rapidly and, as in activation by alkyl groups (Section 16-2), furnish exclusively ortho- and para-... 

For an example of applying this capability in synthetic strategy, consider the preparation of 3-bromobenzenamine. Direct bromination of benzenamine (aniline) leads to complete ortho and para substitution (Section 16-3) and is therefore useless. However, bromination of nitrobenzene allows preparation of 3-bromonitrobenzene, which can be converted into the required target molecule by reduction. The outcome is a benzene derivative in which two ortho, para directors emerge positioned meta to each other. 

How does the benzene ring modify the behavior of neighboring reactive centers This chapter takes a closer look at the effects exerted by the ring on the reactivity of alkyl substituents, as well as of attached hydroxy and amino functions. We shall see that the behavior of these groups (introduced in Chapters 3, 8, and 21) is altered by the occurrence of resonance. After considering the special reactivity of aryl-substituted (benzylic) carbon atoms, we turn our attention to the preparation and reactions of phenols and benzenamines (anilines). These compounds are found widely in nature and are used in synthetic procedures as precursors to substances such as aspirin, dyes, and vitamins. 

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