Reactions of Benzene and Substituted Benzenes

The compound we know as benzene was first isolated in 1825 by Michael Faraday. He extracted it from the liquid residue obtained after heating whale oil under pressure to produce the gas then being used in gas lamps. In 1834, Eilhard Mitscherlich correctly determined the molecular formula of Faraday s compound and named it benzin 

We have seen that the families of organic compounds can be placed in one of four groups, and that all the families in a group react in similar ways (Section 5.6). This chapter begins our discussion of aromatic compounds—the families of compounds in Group IV. 

In Chapter 8, you learned that benzene is an aromatic compound that can be represented by two resonance contributors. You saw that to be aromatic, a compound must be cyclic and planar and have an unintermpted cloud of rr electrons (called a tt cloud) above and below the plane of the molecule, and the tt cloud must contain an odd number of pairs of TT electrons (Section 8.8). You also learned that aromatic compounds are unusually stable compounds (Section 8.7). 

Many substituted benzenes are found in nature. A few that have physiological activity are shown here. 

OH adrenaline epinephrine a hormone released by the body in response to stress 

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Trifluorodi(phenyl)-A5-stibane is also prepared by treating fluorodi(phenyl)stibane with xenon difluoride (in 98 % yield)10 1 or (difluoroiodo)benzene (in 70% yield).107 The reaction of benzene and substituted benzenes with antimony(V) fluoride has been used to prepare the corresponding diaryltrifluoro-/5-stibane hydrates but in yields as low as 7-20%.108... 

Reactions of benzene and substituted benzenes are diseussed in Chapter 7... 

Chapter 19 focuses on the reactions of benzene and substituted benzenes. Although benzene, alkenes, and dienes are all nncleophiles (becanse they all have carbon-carbon tt bonds), benzene s aromaticity causes it to react in a way that is qnite different from the way alkenes and dienes react You will see how a substituent can be placed on a benzene ring and some reactions that can change the substiment after it is on the ring. You will also learn how a substituent affects both the reactivity of a benzene ring and the placement of an incoming snbstituent Chapter 19 also describes two additional types of reactions that can be used to synthesize snbstituted benzenes the reactions of arene diazonium salts and nucleophilic aromatic substitution reactions. 

The reactions of benzene and substituted benzenes now come after carbonyl chemistry. This allows the two chapters that discuss compounds in Group IV (aromatic compounds) to be adjacent. Coverage of oxidation-reduction reactions, hpids, and dmg discovery and design have been integrated into early chapters where appropriate. 

The imidazolium chloroaluminate ionic liquid was also found to be effective as an unconventional reaction media and as Lewis acid catalyst for the Friedel-Crafts sulfonylation reaction of benzene and substituted benzene with p-toluenesulfonyl chloride giving rise to the diarylsulfones in high yield (Scheme 6.14) [16]. 

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