Aromatic compounds, naming

P 23] The nitration of two standard aromatic compounds, namely benzene and toluene, was performed utilizing nitric acid/sulfuric acid mixtures and the pure... 

Polycyclic aromatic compounds, namely naphthalene, anthracene and pyrene derivatives are widely used as fluorescent probes in relevant biomolecules. 

The reduction of three polynuclear aromatic compounds, namely, perylene, decacyclene, and dibenzothiophene, with potassium metal in tetrahydrofuran at 25 °C, followed by quenching with alkyl iodides, was investigated. With perylene, a dianion was obtained, which on reaction with methyl iodide added two methyl groups the main re-gioisomer had one methyl group on C-l and one methyl group on the adjacent nonprotonated carbon, C-14. The reductive alkylation of decacyclene also led to alkyl groups on quaternary carbon atoms. The reduction of dibenzothiophene led to a loss of sulfur and proton uptake from solvent to yield biphenyl as the product after 24 h of reduction. 

Naming Aromatic Compounds Name the aromatic compound shown. 

The most critical separation problem is the separation of all the n-alkanes from the most volatile aromatic compound, namely benzene. To be able to achieve the separation shown in Figure 11.20, the separation factors of all n-alkanes with... 

HMO theory is named after its developer, Erich Huckel (1896-1980), who published his theory in 1930 [9] partly in order to explain the unusual stability of benzene and other aromatic compounds. Given that digital computers had not yet been invented and that all Hiickel s calculations had to be done by hand, HMO theory necessarily includes many approximations. The first is that only the jr-molecular orbitals of the molecule are considered. This implies that the entire molecular structure is planar (because then a plane of symmetry separates the r-orbitals, which are antisymmetric with respect to this plane, from all others). It also means that only one atomic orbital must be considered for each atom in the r-system (the p-orbital that is antisymmetric with respect to the plane of the molecule) and none at all for atoms (such as hydrogen) that are not involved in the r-system. Huckel then used the technique known as linear combination of atomic orbitals (LCAO) to build these atomic orbitals up into molecular orbitals. This is illustrated in Figure 7-18 for ethylene. 

When large concentrations of water are added to the solutions, nitration according to a zeroth-order law is no longer observed. Under these circumstances, water competes successfully with the aromatic for the nitronium ions, and the necessary condition for zeroth-order reaction, namely that all the nitronium ions should react with the aromatic as quickly as they are formed, no longer holds. In these strongly aqueous solutions the rates depend on the concentrations and reactivities of the aromatic compound. This situation is reminiscent of nitration in aqueous nitric acid in which partial zeroth-order kinetics could be observed only in the reactions of some extremely reactive compounds, capable of being introduced into the solution in high concentrations ( 2.2.4). 

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... 

Cyclic compounds that contain at least one atom other than carbon within their ring are called heterocyclic compounds, and those that possess aromatic stability are called het erocyclic aromatic compounds Some representative heterocyclic aromatic compounds are pyridine pyrrole furan and thiophene The structures and the lUPAC numbering system used m naming their derivatives are shown In their stability and chemical behav lor all these compounds resemble benzene more than they resemble alkenes... 

Many aromatic compounds are simply substituted derivatives of benzene and are named accordingly Many others have names based on some other parent aromatic compound... 

Monocyclic Aromatic Compounds. Except for six retained names, all monocyclic substituted aromatic hydrocarbons are named systematically as derivatives of benzene. Moreover, if the substituent introduced into a compound with a retained trivial name is identical with one already present in that compound, the compound is named as a derivative of benzene. These names are retained ... 

Diketones and tetraketones derived from aromatic compounds by conversion of two or four SCH groups into keto groups, with any necessary rearrangement of double bonds to a quinonoid structure, are named by adding the suffix -quinone and any necessary affixes. 

The most important method for the synthesis of aromatic ketones 3 is the Friedel-Crafts acylation. An aromatic substrate 1 is treated with an acyl chloride 2 in the presence of a Lewis-acid catalyst, to yield an acylated aromatic compound. Closely related reactions are methods for the formylation, as well as an alkylation procedure for aromatic compounds, which is also named after Friedel and Crafts. 

Another formylation reaction, which is named after Gattermann, is the Gatter-mann-Koch reaction. This is the reaction of an aromatic substrate with carbon monoxide and hydrogen chloride (gas) in the presence of a Lewis acid catalyst. Similar to the Gattermann reaction, the electrophilic agent 9 is generated, which then reacts with the aromatic substrate in an electrophilic aromatic substitution reaction to yield the formylated aromatic compound 10 ... 

This substance is an aromatic compound, similar to the ethel-ether, and is a useful fixative. It has been sold under the name Fragarol. 

Table 15.1 Common Names of Some Aromatic Compounds...

Note in the second and third examples showm that -phenol and -toluene are used as the parent names rather than -benzene. Any of the monosubstituted aromatic compounds shown in Table 15.1 can serve as a parent name, with the principal substituent (-OH in phenol or -CHj in toluene) attached to Cl on the ring. 

The term aromatic is used for historical reasons to refer to the class of compounds related structurally to benzene. Aromatic compounds are systematically named according to TUPAC rules, but many common names are also used. Disubstituted benzenes are named as ortho (1,2 disubstituted), meta (1,3 disub-stituted), or para (1,4 disubstituted) derivatives. The C6H5- unit itself is referred to as a phenyl group, and the Cb f5CH2— unit is a benzyl group. 

Draw and name all possible aromatic compounds with the formula C71 l7CI. 

Phenols are named as described previously for aromatic compounds according to the rules discussed in Section 15.1. Note that -phenol is used as the parent name rather than -benzene. 

Griess (1860) coined the prefix diazo for the nitrosation product of an aromatic amine, because he assumed that two nitrogen atoms replaced two hydrogen atoms of the parent aromatic compound. On the other hand, azobenzene received its name on the basis of the C H N ratio 6 5 1, indicating the replacement of one hydrogen by one nitrogen atom. 

EXAMPLE 18.5 Sample Exercise Naming an aromatic compound... 

Aromatic compounds are named by giving the substituents on the benzene ring the lowest numbers. When the benzene ring is itself named as a substituent, it is called a phenyl group. 

Aromatic organic chemistry is a special branch of organic chemistry because the six-membered carbon rings that define aromatic compounds are exceptionally stable and act as central supports to which other groups can be attached. The name aromatic was given to early isolated examples of these compounds because they have characteristic odors. 

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