Benzene and Substituted Benzenes

Hydrogenolysis of the C-0 bond is not observed when the benzene rings of benzyl alcohols and ethers are hydrogenated under these conditions, particularly when a small amount of acetic acid is added to the reaction mixture.4.5 Under these conditions the hydrogenation of the benzene ring of 

Selective Hydrogenation of Benzene to Cyclohexene Obtaining trans substituted cyclohexanes suggested that desorbed cyclohexenes were intermediates in the hydrogenation of benzenes. The isolation of cyclohexene and substituted cyclohexenes from the hydrogenation of benzene and substituted benzenes was first reported for hydrogenations run over a Ru/C catalyst, but the maximum olefin concentrations observed in this early work were only 0.2-3.4%.7 

Most partial benzene hydrogenations use a ruthenium catalyst since it is a good species for promoting the hydrogenation of aromatic systems but not very effective for double bond saturation. The reaction is commonly run at 150°-200°C under 10-70 atmospheres of hydrogen. The maximum cyclohexene formation of about 40-70% selectivity is usually observed at low to moderate 

Zinc salts have also been employed as modifiers.2 -26 A very selective catalyst was prepared by treating a mixture of RUCI3 and ZnCl2 with NaOH and 

Modifiers have also been used to influence the selectivity of vapor-phase partial hydrogenations of benzene. The presence of ethylene glycol increased reaction selectivity with a ruthenium black catalyst from 7% to 41% while the turnover frequency (TOF) decreased from 31 to 3. Pyridine also increased selectivity in the short term, but prolonged use poisoned the catalyst. Passivating a ruthenium black catalyst with caprolactam not only stabilized the catalyst toward deactivation but also increased reaction selectivity from 7% to 20%. 

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Benzene and substituted benzenes reaet with electrophiles, leading to new functionality. The two-step mechanism involves initial attack by an electrophile to form an intermediate (benzenium ion), followed by elimination of a proton to generate the substituted benzene. 

Benzene (CeHg) is the simplest aromatic hydrocarbon and by far the most widely used one. Before 1940, the main source of benzene and substituted benzene was coal tar. Currently, it is mainly obtained from catalytic reforming. Other sources are pyrolysis gasolines and coal liquids. 

The most common reaction of aromatic compounds is electrophilic aromatic substitution. That is, an electrophile reacts with an aromatic ring and substitutes for one of the hydrogens. The reaction is characteristic of all aromatic rings, not just benzene and substituted benzenes. In fact, the ability of a compound to undergo electrophilic substitution is a good test of aromaticity- . 

In a related procedure, even benzene and substituted benzenes (e.g., PhMe, PhCl, xylenes) can be converted to phenols in good yields with sodium perborate F3CS020H. " Aromatic amines, N-acyl amines, and phenols were hydroxylated with H2O2 in SbFs—HF. Pyridine and quinoline were converted to their 2-acetoxy derivatives in high yields with acetyl hypofluorite AcOF at -75°C. ... 

There is no experimental evidence for 7r-complexation of arenes to gold centers in the condensed phase. Quantum-chemical calculations were carried out on various levels of theory for 1 1 and 2 1 complexes of benzene and substituted benzenes with Au+ in the gas phase. For all model systems investigated, it has been predicted that an -coordination to a single carbon atom is the ground state of the cation (Cy-symmetry for [(C6H6)Au]+ and 6 -symmetry for [(C6H6)2Au] ). Similar results were obtained for hexafluorobenzene, for which a coordina-... 

While benzene and substituted benzenes usually do not dimerize, pyridine derivatives undergo [4+4]photodimerizations432) (4.29). 

Aromatic hydrocarbon a hydrocarbon characterized by the presence of an aromatic ring or condensed aromatic rings benzene and substituted benzene, naphthalene and substituted naphthalene, phenan-threne and substituted phenan-threne, as well as the higher condensed ring systems compounds that are distinct from those of aliphatic compounds (q.v.) or ali-cyclic compounds (q.v.). 

The chlorinated intermediate 255 is eliminated and cycloadds to Cjq, yielding pyrazo-linofullerenes of the structure 257 (Scheme 4.42). The 4-nitrophenyl-group can be replaced by a 4-methoxyphenyl- or a phenyl substituent. In this reaction various aromatics and substituted aromatics are tolerated as residues R (e.g. furan, ferrocene, pyrazole or benzene and substituted benzene). The nitro group of the nitrophenyl residue can be reduced with Sn-HCl to the aniline derivative, which can be further functionalized by amide coupling with acid chlorides [311]. 

TEVES has been used to treat soils contaminated with laboratory-generated organic wastes including alcohols, aldehydes, amines, ketones, benzene and substituted benzenes, ethers, phenols, polymers, and heterocyclic compounds. The largest volume of organic wastes treated were volatile organic compounds (VOCs) and various types of oils (hydraulic, transformer, heat transfer fluid, and motor oils). 

Benzene under Benzene and Monosubstituted Benzene Hydrocarbons Benzene and Monosubstituted Benzene Hydrocarbons Benzene and Substituted Benzene Hydrocarbons Benzene, Toluene, Ethylbenzene, and Xylene (BTEX)... 

Reaction of Carbon with Benzene and Substituted Benzenes. 479... 

C-H Insertion versus Double-Bond Addition in the Reaction of Carbon with Aromatics. The factors that determine if C atoms react with an aromatic by C—H insertion or DBA are not yet understood. Benzene and substituted benzenes are postulated to react by C—H insertion although detailed labeling studies have only been carried out in benzene, toluene, and ferf-butylbenzene. No C—H insertion is observed in the reaction of carbon with 71, while C—H insertion is a minor pathway when carbon reacts with 76 and 87. 

Nuclear oxidation of benzene and substituted benzenes by this system leads to the selective formation of phenol and substituted phenols. In this case hydrogen peroxide was either generated electrochemically or it was added while the... 

Trifluorodi(phenyl)-A5-stibane is also prepared by treating fluorodi(phenyl)stibane with xenon difluoride (in 98 % yield)10 1 or (difluoroiodo)benzene (in 70% yield).107 The reaction of benzene and substituted benzenes with antimony(V) fluoride has been used to prepare the corresponding diaryltrifluoro-/5-stibane hydrates but in yields as low as 7-20%.108... 

IV. EXPERIMENTAL EVIDENCE FOR THE ISOMERIZATION ROUTE FROM BENZENE AND SUBSTITUTED BENZENES... 

The aromatic silylation of benzene and substituted benzenes by Me3Si+ have been studied by several groups. In a high-pressure mass-spectrometric study, Stone and Stone144... 

In the case of benzene and substituted benzene, attack of a first molecule of ozone is slow but the resulting molecule reacts more rapidly since they belong to the group of olefins. At the end of the reaction, the peroxidic compounds are unstable and contain different products coming from more than one mode of ozone attack [40-43] and competing reaction leading to perox-... 

Aromatic compounds are especially stable and are, therefore, important persistent pollutants. They include the polyaromatic hydrocarbons (PAHs), and may be halogenated, such as the polychlorinated biphenyls (PCBs) and many pesticides. Also included are the substituted benzenes, such as phenol. A large body of literature has examined aromatic radiation chemistry [22— 38]. The discussion that follows examines benzene and substituted benzenes as a model for the radiolysis of more complicated aromatic compounds. 

Benzene and substituted benzenes normally act as six-electron donors, although dihapto and tetrahapto complexes are also known. Dibenzenechromium was prepared eariy in this century but was not characterized until 1954. It was first synthesized via a Grignard synthesis. When PhMgBr reacts with CrClj in diethylelher solvent, a mono-hapto complex [CrPh lEt O) ] forms which rearranges. presumably by a free radical reaction to give, among other products, This ion can be reduced... 

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