Aromatic compounds monosubstituted benzenes

Aromatic compounds like benzene undergo a highly characteristic reaction called electrophilic substitution. For example, halogens, such as chlorine and bromine, instead of simply adding to the formal double bonds as if it were an olefin (i.e. electrophilic addition in which both halogen atoms add to the double bond), displace one of the hydrogen atoms to give a monosubstituted aryl halide... 

It is a typically aromatic compound and gives addition and substitution reactions more readily than benzene. Can be reduced to a series of compounds containing 2-10 additional hydrogen atoms (e.g. tetralin, decalin), which are liquids of value as solvents. Exhaustive chlorination gives rise to wax-like compounds. It gives rise to two series of monosubstitution products depending upon... 

Although there are a wide variety of indole ring syntheses (25), most of the more useful examples fall within a small number of groups. Indole syntheses usually start with an aromatic compound, either monosubstituted or ortho-disubstituted. Those which begin with a monosubstituted starting material must at some point effect a substitution of the benzene ring. 

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. 

Soma et al. (12) have generalized the trends for aromatic compound polymerization as follows (1) aromatic compounds with ionization potentials lower than approximately 9.7 eV formg radical cations upon adsorption in the interlayer of transition-metal ion-exchanged montmorillonites, (2) parasubstituted benzenes and biphenyls are sorbed as the radical cations and prevented from coupling reactions due to blockage of the para position, (3) monosubstituted benzenes react to 4,4 -substituted biphenyls which are stably sorbed, (4) benzene, biphenyl, and p-terphenyl polymerized, and (5) biphenyl methane, naphthalene, and anthracene are nonreactive due to hindered access to reaction sites. However, they observed a number of exceptions that did not fit this scheme and these were not explained. 

The irradiation of benzenes with alkenes provides a fascinating array of photochemical reactions, not least because it converts the aromatic substrates into polycyclic, non-aromatic products. In principle, benzene can undergo reaction across the 1,2-(ortho). 1,3-(meta), or 1,4-(para) positions the 1,3-cycloaddition is structurally the most complex, but it is the predominant mode of reaction for many of the simplest benzene/alkene systems. The products are tricyclic compounds with a fusion of two five-membered rings and one three-membered ring, and an example is the reaction of benzene with vinyl acetate (3.411. For monosubstituted benzenes there can be a high... 

A quantitative description of the reactivity of monosubstituted benzenes to electrophilic substitution based on considerations of inductive effect parameters and con-jugative effect parameters from the 13 C chemical shifts of the aromatic compounds has been proposed.3 MO calculations on the proton migration in the ipso adducts formed in the reaction of CH3+ and SiH3+ with benzene have been described.4 With SiH3+ the ipso adduct is the most stable of possible isomers, whereas for CH3+ the >ara-protonated isomer is the most stable. 

Quantitative rate data ample for an adequate test of the applicability of a linear free-energy relationship are now available. Prior to an examination of this question, however, it is convenient to present all the experimental information necessary for a discussion of the problem. The partial rate factors for sixty reactions of toluene, the most intensively studied aromatic compound, were summarized in Table 2. Other monosubstituted benzenes, although less completely investigated than toluene, provide results encompassing a broad range of relative reactivity. The data for the reactions of the simple aromatic... 

The ll NMR spectrum of each isomer shows peaks corresponding to live aromatic protons, so compounds A and B each contain a monosubstituted benzene ring. Only four compounds of molecular formula C8HnN meet this requirement. 

Name and write the structures for aromatic compounds, especially monosubstituted and disubstituted benzenes and toluenes. 

The vast majority of reactivities and regioselectivities observed in the reaction with electrophiles on monosubstituted benzenes (Table 5.2) are in agreement with the preceding generalizations (columns 2 and 4). The very few substituents that are not in agreement (column 3) deactivate the aromatic compound as do electron acceptors, but they are para- > ortho-directing as are electron donors. 

The condensation of tellurium tetrachloride with aromatic compounds was one of the first methods for the preparation of aryl tellurium trichlorides. Alkyl aryl ethers react easily with tellurium tetrachloride in refluxing chloroform or carbon tetrachloride (Vol. IX, p. 1153). The trichlorotelluro group enters in the /wa-position to the alkoxy group. Several additional monosubstituted benzenes and substituted phenols were found to condense with tellurium tetrachloride (Table 7, p. 306). 

The compound has nine degrees of unsaturation. The H NMR spectrum shows that the compound is symmetrical and that the only absorptions occur in the vinylic and aromatic regions of the spectrum. The IR spectrum shows peaks due to a monosubstituted benzene ring and to R2C=CH2 (890 cm -1). 

Aromatic compounds are the only type of i-nucleophiles involved in reactions with organoxenonium salts. While pentafluorobenzenes, CeFsZ (Z = H, F, CN, SiMej), are not reactive towards [C6F5Xe][AsF6] in MeCN at 20 °C, a series of 2,3,4,5,6-pentafIuorobiphenyls was obtained from monosubstituted benzene derivatives, CeHsZ, under these conditions. The reaction rates diminish in the sequence Z = CH3 > F > CF3 CN > NO2, which is consistent with the electrophilic nature of the process. Nevertheless, the isomer distribution in the C6F5C6H4Z products shows unambiguously the radical character of the pentafluorophenylation reaction (eq 17) 46). 

The substitution of pure benzene by an electrophile will result in the formation of a monosubstituted product, which is capable of undergoing further substitution reactions. When designing the strategy for the synthesis of an aromatic compound, there are two principal points that must be borne in mind, namely first, the reactivity of the monosubstituted product compared with that of the original benzene and second, the position on the aromatic ring where the second substitution reaction will take place. These two issues will now be examined, and it will be seen that they are, at least to some extent, dependent upon each other. 

The pioneering work of a coupling of aromatic and heteroaromatic compounds with acetylenes was reported by Yamazaki et al. in 1979 [35]. Reaction of benzene with diphenylacetylene gives triphenylethene in 45% yield. In the case of the monosubstituted benzene, the reaction of toluene proceeds at the meta position selectively but the reaction of anisol takes place at the ortho position (Eq. 21). They proposed that the site-selectivity stems from an inductive effect of an elec-... 

No reaction involving monosubstituted benzenes has been reported. The results are presented according to the substituent positions in the starting aromatic compound. 

To get an idea of such a prediction process, we will look at a result for the prediction of a monosubstituted benzene derivative. The data set for this experiment contains 50 benzene derivatives and their spectra-descriptor pairs. Figure 6.5 shows the infrared spectrum of the query compound reduced to 128 components by the FHT method described already. The spectrum contains some bands that may indicate the existence of an aromatic system and of halogen atoms. However, the spectrum is not particularly characteristic. 

Benzene, C6H6, is the prototype of aromatic compounds, which are unsaturated compounds showing a low degree of reactivity. The Kekule structure (1865) for benzene has only one monosubstituted product ... 

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