Hydrocarbon functional groups benzene ring

The simplest aromatic hydrocarbon is benzene. The six-membered ring and three n bonds of benzene comprise a single functional group. Benzene is a component of the BTX mixture (B for benzene) added to gasoline to boost octane ratings. 

Now let us examine the aromatic hydrocarbons (Figure 14.20). Again, the benzene ring is the structural feature that identifyies a hydrocarbon as aromatic (i.e., it is the aromatic hydrocarbon functional group). The benzene... 

The aromatic hydrocarbons contain at least one unsaturated ring system with the general structure C6R6, where R is any functional group (see Chap. 1). The parent hydrocarbon of this class of compounds is benzene (C6H6), which exhibits the resonance, or delocalization of electrons, typical of unsaturated cyclic structures. Owing to its resonance energy, benzene is remarkably inert. 

Because the unsaturated hydrocarbon has to bind to rhodium in the presence of bulky PPh3 groups, the catalyst favours unsubstituted double bonds (RCH=CH2 rather than RR C=CR r ). Since the alkyl intermediate is shortlived, there is little tendency to / -elimination with concomitant alkene isomerization. Although both alkene and alkyne functions are reduced, in general carbonyl or carboxylic groups and benzene rings are not, though aldehydes are frequently decarbonylated. Peroxides tend to oxidize and thus destroy the catalyst, so that substrates need to be purified carefully before use. 

The simplest aromatic hydrocarbon is benzene. The six-membered ring and three n bonds of benzene comprise a single functional group. 

It would appear that most of the benzene ring structures in humic substances have two or more substituents, such as carbonyl, carboxyl, hydrocarbon, hydroxyl, and methoxyl and other ether functional groups. The evidence from identification of the products of degradation reactions, and more recently from NMR data, suggests that aliphatic hydrocarbons and aliphatic and aromatic ether groups link the core components in the macromolecules, and that carbonyl, carboxyl, and hydroxyl substituents are likely to be attached to some of the aliphatic hydrocarbons (Hayes and Swift, 1978). 

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