Benzene derivatives structural formulae

Polynuclear aromatic hydrocarbons. These consist of a variety of complex structures made up of aromatic rings alone, or combinations of aliphatic rings, aromatic rings, and aliphatic chains, etc. One such class of compounds is biphenyl and its derivatives, in which two benzene rings are connected by a single C — C linkage. The structural formula of biphenyl (or phenylbenzene) is... 

Exercise 22-7 Establish the structures of the following benzene derivatives on the basis of their empirical formulas and nmr spectra shown in Figure 22-6. Remember that equivalent protons normally do not split each other s resonances, a. C8H10 b. C8H7OCI c. C9FI10O2 d. C9hl12... 

Phenols and derivatives are the main aromatic compounds of plants, whose structural formulas contain at least one benzene ring. They serve as odors, fungicidals, or germination inhibitors. Coumarins are especially common in grasses, orchids, citrus fruits, and legumes. Plants containing phenols with anticancer properties include the following ... 

Figure 13.7 shows the structural formulas of benzene and its major hydrocarbon derivatives. These compounds are very significant in chemical synthesis, as solvents, and in unleaded gasoline formulations. 

As seen from the structural formulas in Figure 16.4, the organochlorine insecticides are of intermediate molecular mass and contain at least one aromatic or nonaromatic ring. They can be placed in four major chemical classes. The first of these consists of the chloroethylene derivatives, of which DDT and methoxychlor are the prime examples. The second major class is composed of chlorinated cyclodiene compounds, including aldrin, dieldrin, and heptachlor. The most highly chlorinated members of this class, such as chloredecone, are manufactured from hexachlorocyclo-pentadiene (see Section 16.3). The benzene hexachloride stereoisomers make up a third class of organochlorine insecticides, and the third group, known collectively as toxaphene, constitutes a fourth. 

Analysis of the data on C6o fullerene solubility in methyl derivatives of benzene has revealed that this magnitude depends not only on the number of CH3-groups, but also on their position in the benzene core. Fig. 2-6 show the structural formulae for methyl derivatives of benzene, the positions of methyl groups and the magnitudes of C6o solubility [1],... 

The Aromatic Hydrocarbons. These hydrocarbons are also cyclic and may be considered to be derivatives of benzene. Benzene has the formula CgHe, and the structure is as depicted. It consists of a six-... 

Terpinenes, Phellandrene, Sylvestrene.—Other less common terpa-di-enes are the terpinenes found in cardamon oil phellandrene in fennd oil and eucalyptus oil and sylvestrene in Swedish and Russian turpentine and in pine needle oil. Sylvestrene differs from the other terpenes that have been given in that it is a derivative of meta-cymene, i-methyl 3-isopropyl benzene, and not of para-cymene. The structural formulas of the above terpa-di-enes are as follows ... 

The ease of transformation ofthe dinaphtho compound 32 (104.8 kJ mol-1 Table 6) relative to the dibenzopyran 27 (126.8 kJ mol1 Table 5) suggests that for the benzonaphtho compounds in Table 8 opening ofthe pyran ring condensed to naphthalene, rather than the one condensed to benzene, will be preferred, as indicated by the arrow in the structural formula of Table 8. Indeed, the AG value for the dimethyl derivative 39 (106.9 kJ mol-1 Table 8) is close to the value obtained for 32 (104.8 kJ mol--1 Table 6). Removal of the methyl groups in 39 results in the spirobipyran 42 and reduces the barrier by approximately 20 kJ mol -1 (Table 8). The same reduction was observed for 27 and 5, containing benzene rings (Table 5). 

The oxidation of benzene and its derivatives has been the subject of careftil investigation ever since the structural formula for an aromatic complex was first suggested by Kekule. The results of these many and varied experiments have served to show that in the case of all such compounds the phenomena of oxidation are very complex. Even benzene itself under the influence of oxidizing agents reacts under different conditions to give a great variety of different products. 

Benzene s particular hexagonal structure is found throughout nature in many forms, almost always in a more complicated way and usually connected to many other " benzene rings" to form many exotic compounds. Benzene s derivatives include toluene and xylene. Some typical properties are given in Table 3.9, which illustrates the differences caused by molecular weight and structural formulas. There are other cyclical hydrocarbons, but they do not have the structural formulas of the aromatics unless they are benzene-based. These cyclical hydrocarbons may have three, four, five, or seven carbons in the cyclical structure in addition to the six-carbon ring of the aromatics. None of them have the stability or the chemical properties of the aromatics. 

The difference between the action of oxidizing agents on the nitro derivative and the amino derivative is observed in the case of other compounds. Benzene derivatives which contain an amino group are readily decomposed by oxidizing agents, whereas rings which contain nitro groups are stable. The structure of napthalene is expressed by the formula,—... 

DE) is useful as a theoretical index to the empirical resonance energy (RE), would be erroneous under the circumstances that the symmetrical hexagonal structure of benzene is driven by the o framework alone and the n electrons favor a distorted and localized structure. They then derived a formula for RE with a distance-dependent /I parameter. They could show that the proportionality between RE and DE exists only under the assumption of a constant /I. They criticized the Hess—Schaad justification of the HSRE at the Hiickel level, because their results would show erroneously that the a-compression energy favors a distorted and localized structure. Later they worked out these ideas in more detail ° with the inclusion of o energies. They concluded that... 

Baeyer showed that reduced benzene rings acquire aliphatic properties. At first he adopted a centric formula for benzene in place of Kekule s (see p. 804), but as a result of this mass of work he announced in 1892 that no conclusion as to the structure of benzene derivatives can be drawn from their behaviour on reduction . In the course of this work he prepared cis- and mw -derivatives of hexahydrophthalic acid and introduced the names cis-and tram-. 

In both representations, it is understood that there is a carbon atom and a hydrogen atom at each comer of the hexagon. The classical Kekule structure is represented by A the modem molecular orbital structure is represented by B. These hexagonal structures are also used to represent the structural formulas of benzene derivatives— that is, substances in which one or more hydrogen atoms in the ring have been replaced by other atoms or groups. Chlorobenzene (CsHsCl), for example, is written in this fashion ... 

The chemistry of benzene and its derivatives is quite different from that of alkenes and alkynes. Even though we do not study the chemistry of arenes until Chapter 9, we will show structural formulas of compounds containing benzene rings in earlier chapters. What you need to remember at this point is that a benzene ring is not chemically reactive under any of the conditions we describe in Chapters 4-8. 

For chemists in the mid-nineteenth century, the problem was to incorporate these observations, along with the accepted tetravalence of carbon, into a structural formula for benzene. Before we examine their proposals, we should note that the problem of the structure of benzene and other aromatic hydrocarbons has occupied the efforts of chemists for over a century. It was not until the 1930s that chemists developed a general understanding of the unique structure and chemical properties of benzene and its derivatives. 

The preparation of benzene derivatives containing ortho-substituted t-butyl groups via cobalt complexes of the formula type Co2(CO) [acetylene] has raised questions of the structural arrangements in these complexes. The analysis of Co2(CO) [Bu C HyHC2H], from which ortho-di t-butylbenzene is obtained, has been shown to involve six carbon atoms bonded bifunctionally... 

Most L-tryptophan-derived secondary products still possess the indole ring system of this amino acid. Some compounds, however, are quinoline, pyrrole or benzene derivatives. Additional rings may be present yielding complicated structures, like that of ergoline and / -carboline alkaloids (cf. the formulas of ergotamine, Corynanthe, Strychnos, Iboga and Aspidosperma-type alkaloids). 

Benzene (1) is a hydrocarbon with the formula CeHg. It is the parent of a large class of compounds known as aromatic hydrocarbons. The structure and chemical reactivity of aromatic hydrocarbons are so unique that benzene derivatives are given their own nomenclature system. The discussion will begin with the unique structure of benzene. 

Aromatic hydrocarbons are hydrocarbons that are derived from benzene (CgHg). The structural formula for benzene is the following ... 

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