Interesting Aromatic Compounds

The number of signals (lines) in the C NMR spectrum of a disubstituted benzene with two identical groups indicates whether they are ortho, meta, or para to each other. 

BTX contains benzene, toluene, and xylene (the common name for dimethylbenzene). 

Benzene and toluene, the simplest aromatic hydrocarbons obtained from petroleum refining, are useful starting materials for synthetic polymers. They are two components of the BTX mixture added to gasoline to boost octane ratings. 

Compounds containing two or more benzene rings that share carbon-carbon bonds are called polycyclic aromatic hydrocarbons (PAHs). Naphthalene, the simplest PAH, is the activ ,ingre-dient in mothballs. 

Benzo[a]pyrene, produced by the incomplete oxidation of organic compounds in tobacco, is found in cigarette smoke. 

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A four-membered ring fused to a benzyne has a sizable directing effect for the regioselective reactions with ketene silyl acetals, nucleophiles, and a-alkoxyfuran. Such findings open up an opportunity for selective syntheses of various interesting aromatic compounds. 

In 1933 Herzberg and Teller demonstrated that certain electronic transitions which are forbidden in the fixed nuclei approximation may attain a non-zero transition probability through the interaction of electronic and nuclear motions. What they essentially did was to note that in every molecule there exist asymmetric nuclear displacements which yield a non-zero expectation value for the gradient of the nuclear-electronic coulombic energy terms. To illustrate their mode of thought we shall here give a pictorial outline of the calculation of such vibronic intensities in two systems of current interest aromatic compounds and transition metal complexes. For the sake of clarity we shall limit our discussion to the exemplary molecular systems of benzene and potassium titanium hexafluoride (KjTiFg). 

For electrophilic substitutions in general, and leaving aside theories which have only historical interest, two general processes have to be considered. In the first, the 5 3 process, a transition state is involved which is formed from the aromatic compound, the electrophile (E+), and the base (B) needed to remove the proton ... 

Ten years ago we became interested in the possibility of using nitration as a process with which to study the reactivity of hetero-aromatic compounds towards electrophilic substitution. The choice of nitration was determined by the consideration that its mechanism was probably better imderstood than that of any other electrophilic substitution. Others also were pursuing the same objective, and a considerable amount of information has now been compiled. 

An interesting aromatic fluoro compound is polytrifluoromethylstyrene, which is claimed to have excellent optical properties (ref. 14). 

An interesting class ot covalent Inflates are vin l and ar>/ or heteroaryl Inflates Vinyl inflates are used for the direct solvolytic generation of vinyl cations and for the generation of unsaturated carbenes via the a-elimination process [66] A triflate ester of 2-hydroxypyridine can be used as a catalyst for the acylation of aromatic compounds with carboxylic acids [109] (equation 55)... 

Indole-2,3-quinodimethanes have also been exploited as the key intermediates in indolo[2,3-a]caibazole synthesis, allowing the preparation of several interesting systems. Thus, when the starting materials 74a-b (obtained from the condensation of protected indole-2-carboxaldehydes with 2-aminostyrene) underwent treatment with methyl chloroformate in hot chlorobenzene, the carbamates 75a-b were obtained, and could subsequently be dehydrogenated into the aromatic compounds 76a-b (Scheme 11). However, all functionalization attempts of the methyl... 

It is of interest that both the methyl affinities and the reactivities of aromatic compounds toward the pheny radical are correlated both by Froax and by atom localization energies. Dewar has shown that the energy required to remove one atom from conjugation (in a hydrocarbon containing an even number of carbon atoms) is greater... 

Wines and other alcoholic beverages such as distillates represent very complex mixtures of aromatic compounds in an ethanol-water mixture. Once an extract or concentrate of the required compounds is prepared, a suitable chromatographic system must be used to allow separation and resolution of the species of interest. Many applications have been developed that use MDGC. 

Another interesting, but rather complex system, which couples flow injection analysis, EC and GC has been recently reported (47). This system allows the determination of the total amount of potentially carcinogenic polycyclic aromatic compounds (PACs) in bitumen and bitumen fumes. This system could also be used for the analysis of specific PACs in other residual products. 

However, it has provided some interesting results. At the top of the tree, the molecule population is first divided according to the presence or absence of the attribute NH2 (primary amine). If the answer is yes , the developed branches (on the right of the tree) mostly leads to the Crownpak CSP. The next attribute is Aromatic . If the answer is no , here the predominant CSP is Chiralpak AD. Aromatic compounds form the largest part of the tree and as expected the dominant CSP is Chiralcel OD which is disseminated in almost every region of the tree. 

Compounds of special interest whose preparation is described include 1,2,3-benzothiadiazole 1,1-dioxide (a benzyne precursor under exceptionally mild conditions), bis(l,3-diphenylimida-zolidinylidene-2) (whose chemistry is quite remarkable), 6- di-melhylamino)julvene (a useful intermediate for fused-ring non-benzenoid aromatic compounds), dipkenylcyclopropenone (the synthesis of which is a milestone in theoretical organic chemistry), ketene di(2-melhoxyethyl) acetal (the easiest ketene acetal to prepare), 2-methylcyclopenlane-l,3-dione (a useful intermediate in steroid synthesis), and 2-phenyl-5-oxazolone (an important intermediate in amino acid chemistry). 

Several examples of [5C+1S] cycloaddition reactions have been described involving in all cases a 1,3,5-metalahexatriene carbene complex as the C5-syn-thon and a CO or an isocyanide as the Cl-synthon. Thus,Merlic et al. described the photochemically driven benzannulation of dienylcarbene complexes to produce ortho alkoxyphenol derivatives when the reaction is performed under an atmosphere of CO, or ortho alkoxyanilines when the reaction is thermally performed in the presence of an isonitrile [111] (Scheme 63). In related works, Barluenga et al. carried out analogous reactions under thermal conditions [36a, c, 47a]. Interestingly, the dienylcarbene complexes are obtained in a first step by a [2+2] or a [3S+2C] process (see Sects. 2.3 and 2.5.1). Further reaction of these complexes with CO or an isonitrile leads to highly functionalised aromatic compounds (Scheme 63). 

Phenol is the starting material for numerous intermediates and finished products. About 90% of the worldwide production of phenol is by Hock process (cumene oxidation process) and the rest by toluene oxidation process. Both the commercial processes for phenol production are multi step processes and thereby inherently unclean [1]. Therefore, there is need for a cleaner production method for phenol, which is economically and environmentally viable. There is great interest amongst researchers to develop a new method for the synthesis of phenol in a one step process [2]. Activated carbon materials, which have large surface areas, have been used as adsorbents, catalysts and catalyst supports [3,4], Activated carbons also have favorable hydrophobicity/ hydrophilicity, which make them suitable for the benzene hydroxylation. Transition metals have been widely used as catalytically active materials for the oxidation/hydroxylation of various aromatic compounds. 

The degradation of aromatic compounds including hydrocarbons and phenols has attracted interest over many years, for several reasons ... 

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