Substituted Derivatives of Benzene and Their Nomenclature

The TT molecular orbitals of benzene arranged in order of increasing energy and showing nodal surfaces. The six tt electrons of benzene occupy the three lowest energy orbitals, all of which are bonding. 

Later in this chapter we ll explore the criteria for aromaticity in more detail to see how they apply to cyclic polyenes of different ring sizes. The next several sections introduce us to the chemistry of compounds that contain a benzene ring as a structural unit. We ll start with how we name them. 

All compounds that contain a benzene ring are aromatic, and substituted derivatives of benzene make up the largest class of aromatic compounds. Many such compounds are named by attaching the name of the substituent as a prefix to benzene. 

Many simple monosubstituted derivatives of benzene have common names of long standing that have been retained in the lUPAC system. Table 11.1 lists some of the most important ones. 

Dimethyl derivatives of benzene are called xylenes. There are three xylene isomers, the ortho o), meta (m)-, and para (p)- substituted derivatives. 

The prefix ortho signifies a 1,2-disubstituted benzene ring, meta signifies 1,3-disubstitution, and para signifies 1,4-disubstitution. The prefixes o, m, and p can be used when a substance is named as a benzene derivative or when a specific base name (such as acetophenone) is used. For example, 

Names of Some Frequently Encountered Derivatives of Benzene 

Dimethyl derivatives of benzene are called xylenes. There are three xylene isomers, 

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The Structure of Benzene 407 The Stability of Benzene 409 Bonding in Benzene 410 Substituted Derivatives of Benzene and Their Nomenclature 412 Polycyclic Aromatic Hydrocarbons 414 Fullerenes, Nanotubes, and Graphene 416-417 Physical Properties of Arenes 416... 

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