Reactions of Arenes A Preview

Thus far, the importance of carbon cluster chemistry has been in the discovery of new knowledge. Many scientists feel that the earliest industrial applications of the fullerenes will be based on their novel electrical properties. Buckminsterfullerene is an insulator, but has a high electron affinity and is a superconductor in its reduced form. Nanotubes have aroused a great deal of interest for their electrical properties and as potential sources of carbon fibers of great strength. 

Although the question that began the fullerene story, the possibility that carbon clusters are formed in stars, still remains unanswered, the attempt to answer that question has opened the door to novel structures and materials. 

FIGURE 11.7 A portion of a nanotube. The ciosed end is approximately one half of a buckyball. The main length cannot close as long as all of the rings are hexagons. 

In general, arenes resemble other hydrocarbons in their physical properties. They are nonpolar, insoluble in water, and less dense than water. In the absence of polar substituents, intermolecular forces are weak and limited to van der Waals attractions of the induced-dipole/induced-dipole type. 

At one time, benzene was widely used as a solvent. This use virtually disappeared when statistical studies revealed an increased incidence of leukemia among workers exposed to atmospheric levels of benzene as low as 1 ppm. Toluene has replaced benzene as an inexpensive organic solvent, because it has similar solvent properties but has not been determined to be carcinogenic in the cell systems and at the dose levels that benzene is. 

We ll examine the chemical properties of aromatic compounds from two different perspectives  

One mode of chemical reactivity involves the ring itself as a functional group and includes 

Reduction of arenes by catalytic hydrogenation was described in Section 11.3. A different method using Group 1 metals as reducing agents, which gives 1,4-cyclohexadiene derivatives, will be presented in Section 11.10. Oxidations of aromatic compounds are discussed in Chapter 22. Electrophilic aromatic substitution is the most important reaction type exhibited by benzene and its derivatives and constitutes the entire subject matter of Chapter 12. 

The unique properties of CNTs, in particular their high surface area and conductivity, have already attracted the attention of researchers in several areas of biology and chemistry. The ability to attach molecules with specific functions to the surfaces of CNTs opens up many possibilities for the applications of these novel materials as nanoscale devices. 

An approach to noncovalent functionalization takes advantage of attractive van der Waals forces to coat the outer surface of a nanotube with a substance that bears the functionality. This approach was successfully demonstrated using a synthetic polymer designed to mimic the properties of mucin. (Mucin is the main substance responsible for the lubricating properties of 

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