Cyclohexane, from benzene reduction preparation

C, b.p. 81"C. Manufactured by the reduction of benzene with hydrogen in the presence of a nickel catalyst and recovered from natural gase.s. It is inflammable. Used as an intermediate in the preparation of nylon [6] and [66] via caprolactam and as a solvent for oils, fats and waxes, and also as a paint remover. For stereochemistry of cyclohexane see conformation. U.S. production 1980 1 megatonne. 

The fusion of a benzene ring to pyrazine results in a considerable increase in the resistance to reduction and it is usually difficult to reduce quinoxalines beyond the tetrahydroquinoxa-line state (91). Two possible dihydroquinoxalines, viz. the 1,2- (92) and the 1,4- (93), are known, and 1,4-dihydroquinoxaline appears to be appreciably more stable than 1,4-dihydropyrazine (63JOC2488). Electrochemical reduction appears to follow a course anzdogous to the reduction of pyrazine, giving the 1,4-dihydro derivative which isomerizes to the 1,2- or 3,4-dihydroquinoxaline before subsequent reduction to 1,2,3,4-tetra-hydroquinoxaline (91). Quinoxaline itself is reduced directly to (91) with LiAlH4 and direct synthesis of (91) is also possible. Tetrahydroquinoxalines in which the benzenoid ring is reduced are well known but these are usually prepared from cyclohexane derivatives (Scheme 30). 

This reaction was first reported by Nenitzescu in 1931. It is the formation of an a,p-unsaturated ketone directly by aluminum chloride-promoted acylation of alkenes with acyl halides. Therefore, it is known as the Darzens-Nenitzescu reaction (or Nenitzescu reductive acylation), or Nenitzescu acylation. Under such reaction conditions, Nenitzescu prepared 2-butenyl methyl ketone from acetyl chloride and 1-butene and dimethylacetylcyclohex-ene from acetyl chloride and cyclooctene. However, in the presence of benzene or hexane, the saturated ketones are often resolved, as supported by the preparation of 4-phenyl cyclohexyl methyl ketone from the reaction of cyclohexene and acetyl chloride in benzene, and the synthesis of 3- or 4-methylcyclohexyl methyl ketone by refluxing the mixture of cycloheptene and acetyl chloride in cyclohexane or isopentane. This is probably caused by the intermolecular hydrogen transfer from the solvent. In addition, owing to its intrinsic strain, cyclopropyl group reacts in a manner similar to an oleflnic functionality so that it can be readily acylated. It should be pointed out that under various reaction conditions, the Darzens-Nenitzescu reaction is often complicated by the formation of -halo ketones, 3,)/-enones, or /3-acyloxy ketones. This complication can be overcome by an aluminum chloride-promoted acylation with vinyl mercuric chloride, resulting in a high purity of stereochemistry. ... 

Here, we present a computational study on Raney-Nickel [1], which is a nanostructured amorphous catalyst used in many industrial applications. It is routinely used in hydrogenation reactions such as the reduction of benzene to cyclohexane. Raney-Nickel is typically prepared by quenching a molten mixture of a NiAl alloy from which Al is leached out for producing the final catalyst The initial alloy precursor composition is important because it affects the NiAl phases formed during the quenching process. These phases have different leaching properties influencing the porosity of the catalyst and thus its performance. 

The difference between the findings of Beinert et al. and Foss et al. is presumably at least in part a reflection of the ability of benzene to provide some degree of solvation to organolithium compounds, in contrast to the extreme inertness of cyclohexane. A similar explanation can be provided" for the successful preparation of O.IM l,4-dilithio-l,l,4,4-tetraphenylbutane from 1,1-diphenylethyIene and lithium metal in benzene after only 48 hours reaction time. When cyclohexane is employed as solvent for this reduction, it is necessary to add substantial amounts of a promoter, such as anisole. 

Being more tolerant to impurities dian aluminium alkoxides, Sn(Oct)2 is widely used for the industrial production of PCL and PLAs mainly in bulk, within batch reactors. Any discussion on die industrial production of polymers has to integrate not only the polymerisation process, but also the monomer production. eCL is prepared by the Baeyer-Villiger oxidation of cyclohexanone (Renz et al, 1999 Rocca et al, 2003), which is produced by the catalytic oxidation of cyclohexane, itself resulting from the catalytic reduction of benzene, made available from oil, a non-renewable resource (Fig. 4.8). 

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