Aromatic compounds sources

Dewar and his co-workers, as mentioned above, investigated the reactivities of a number of polycyclic aromatic compounds because such compounds could provide data especially suitable for comparison with theoretical predictions ( 7.2.3). This work was extended to include some compounds related to biphenyl. The results were obtained by successively compounding pairs of results from competitive nitrations to obtain a scale of reactivities relative to that of benzene. Because the compounds studied were very reactive, the concentrations of nitric acid used were relatively small, being o-i8 mol 1 in the comparison of benzene with naphthalene, 5 x io mol 1 when naphthalene and anthanthrene were compared, and 3 x io mol 1 in the experiments with diphenylamine and carbazole. The observed partial rate factors are collected in table 5.3. Use of the competitive method in these experiments makes them of little value as sources of information about the mechanisms of the substitutions which occurred this shortcoming is important because in the experiments fuming nitric acid was used, rather than nitric acid free of nitrous acid, and with the most reactive compounds this leads to a... 

The thiazolyl radicals are, in comparison to the phenyl radical, electrophilic as shown by isomer ratios obtained in reaction with different aromatic and heteroaromatic compounds. Sources of thiazolyl radicals are few the corresponding peroxide and 2-thiazolylhydrazine (202, 209, 210) (see Table III-34) are convenient reagents, and it is the reaction of an alky] nitrite (jsoamyl) on the corresponding (2-, 4-, or 5-) amine that is most commonly used to produce thiazolyl radicals (203-206). The yields of substituted thiazole are around 40%. These results are summarized in Tables III-35 and IIT36. 

Sulfonation (Section 12 4) Sulfonic acids are formed when aromatic compounds are treated with sources of sulfur trioxide These sources can be concentrated sulfuric acid (for very reactive arenes) or solutions of sulfur trioxide in sulfuric acid (for ben zene and arenes less reactive than ben zene)... 

The precursors of dyes are called dye intermediates. They are obtained from simple raw materials, such as ben2ene and naphthalene, by a variety of chemical reactions. Usually, the raw materials are cycHc aromatic compounds, but acycHc precursors are used to synthesi2e heterocycHc intermediates. The intermediates are derived from two principal sources, coal tar and petroleum (qv). 

The petroleum industry is now the principal suppHer of ben2ene, toluene, the xylenes, and naphthalene (see BTX processing Feedstocks). Petroleum displaced coal tar as the primary source for these aromatic compounds after World War II because it was relatively cheap and abundantly available. However, the re-emergence of king coal is predicted for the twenty-first century, when oil suppHes are expected to dwindle and the cost of producing chemicals from coal (including new processes based on synthesis gas) will gradually become more competitive (3). 

The generation of caibocations from these sources is well documented (see Section 5.4). The reaction of aromatics with alkenes in the presence of Lewis acid catalysts is the basis for the industrial production of many alkylated aromatic compounds. Styrene, for example, is prepared by dehydrogenation of ethylbenzene made from benzene and ethylene. 

Virgin Naphtha Catalytic Reforming (Powerfortning) This technique is used for the production of high octane motor gasoline, or as a source of aromatic compounds. 

The term Birch reduction was originally applied to the reduction of aromatic compounds by alkali metals and an alcohol in ammonia. In recent years many chemists have used the term to include all metal-ammonia reductions, whether an alcoholic proton source is present or not. The author prefers to use the term Birch reduction to designate any reduction carried out in ammonia with a metal and a proton donor as or more acidic than an alcohol, since Birch customarily used such a proton donor in his extensive pioneering work. The term metal-ammonia reduction is best reserved for reductions in which ammonia is the only proton donor present. This distinction in terminology emphasizes the importance of the acidity of the proton donor in the reduction process. 

Simple aromatic hydrocarbons come from two main sources coal and petroleum. Coal is an enormously complex mixture made up primarily of large arrays of benzene-like rings joined together. Thermal breakdown of coal occurs when it is heated to 1000 °C in the absence of air, and a mixture of volatile products called coal for boils off. Fractional distillation of coal tar yields benzene, toluene, xylene (dimethylbenzene), naphthalene, and a host of other aromatic compounds (Figure 15.1). 

Starting with benzene as your only7 source of aromatic compounds, how would you synthesize the following substances Assume that you can separate ortho and para isomers if necessary. 

The metabolic processes underpinning the catabolism of aliphatic and aromatic compounds are described in the BIOTOL text "Energy Sources for Cell". 

Bruhn C, H Lenks, H-J Knackmuss (1987) Nitrosubstituted aromatic compounds as nitrogen source for bacteria. Appl Environ Microbiol 53 208-210. 

Application of NMR has been made to a restricted range of chlorinated aromatic compounds (Kolehmainen et al. 1992), and has been used to establish the source of oxygen in the metabolites produced from acetate and 02 by Aspergillus melleus (Staunton and Sutkowski 1991). 

Before the advent of the petrochemical industry carbocyclic aromatic compounds, such as naphthalene, phenol, and pyridine, provided the source of many important industrial chemicals including dyestuffs, while the monocyclic compounds continue to play an important role as fuels and starting materials. 

Phenols also constitute a major source of xenobiotic exposure to the body in the form of drugs and environmental pollutants. Oxidative metabolism of these compounds can lead to physiological damage, therefore the metabolism of these compounds is of great interest. LCEC has been a powerful tool for investigating the metabolism of aromatic compounds by the cytochrome P-450 system LCEC... 

Dissolving-Metal Reduction of Aromatic Compounds and Alkynes. Dissolving-metal systems constitute the most general method for partial reduction of aromatic rings. The reaction is called the Birch reduction,214 and the usual reducing medium is lithium or sodium in liquid ammonia. An alcohol is usually added to serve as a proton source. The reaction occurs by two successive electron transfer/proto-nation steps. 

Any nitro- or amino-aromatic compound may be considered a potential source of interference until demonstrated otherwise. For example, DN-111 in benzene was processed in the usual manner. During the reduction step a pink color developed which was insoluble in petroleum ether addition in proper sequence of the dye-producing reagents resulted in the development of a deep purple color within 10 minutes. 

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