Cyclohexane, conversion Into benzene

The fluorination of cyclohexane probably takes place via an initial conversion into benzene, brought about by the fluorinating agent, as under certain conditions (CeF4 at 300 C, a temperature at which benzene does not fluorinate over this reagent) benzene can be isolated as the near-sole product.42 If cyclohexane is first converted into benzene, then all fluorinations of saturated compounds might also proceed via an initial desaturation step this point is touched on several times throughout Section 25.1. The products are much the same as those obtained from benzene (Section 25.1.1.2.). 

The total hydrogenation of benzene derivatives represents an important industrial catalytic transformation, in particular with the conversion of benzene into cyclohexane, a key intermediate in adipic acid synthesis, which is used in the production of Nylon-6,6 (Scheme 1). This reaction is still the most important industrial hydrogenation reaction of monocyclic arenes [1]. 

The solid is used as a heterogeneous catalyst or as a water-soluble system in biphasic conditions in the hydrogenation of benzene and pheny-lacetylene [65]. The heterogeneous system Rh-PVP is investigated in the solid/liquid catalytic hydrogenation of benzene with a ratio of 1/34000 at 80 °C and 20 bar H2. The conversion into cyclohexane is about 60% after 200 h of reaction time. In a water/benzene biphasic condition at 30 °C and under 7 bar H2, complete hydrogenation (Scheme 2) for a molar ratio of 2000 is observed after 8 h giving a TOF = 675 h (related to H2 consumed), never-... 

The VEEL spectra of the species formed from cyclohexane on Pt(lll) show that at least two intermediate species occur along the decomposition pathway to benzene. These spectra are discussed in Sections VI.A and VI.C, in the context of spectra of species formed from adsorbed cyclohexene (239) and cyclo-l,3-hexadiene (240) on the same surface. On Pt(100) hex, in contrast to Pt(lll), most of the cyclohexane molecules desorb before conversion to benzene, but the latter was formed after adsorption at 300 K. An intermediate in the conversion of cyclohexane into benzene on Pt(100) (1 X 1), stable between ca. 200 and 300 K, was recognized spectroscopically, but not structurally identified, by RAIRS (230) and by VEELS (224). It seems that there is a smooth transition from the spectrum of adsorbed cyclohexane on Pd(100) to that of benzene at temperatures exceeding 250 K without the detection of intermediate spectra (220). 

Scheme 7.2 Homodesmotic equation for conversion of cyclohexa-1,3-diene and cyclohexene into benzene and cyclohexane.

Azomethane imines undergo an analogous photoinduced cyclization to give diaziridines. The dihydroisoquinoline derivative (99), for example, is converted on irradiation in cyclohexane or benzene into the diaziridine (100) the transformation is thermally reversible. In contrast, the pyrazolidinone azomethine imines (101) undergo photoreversible conversion into the diaziridines (102), providing in this way a useful reversible photochromic system. The analogous photoisomerization of a pyrene-substituted pyrazolidinone azomethinimine has... 

The application of carbon membrane reactors for the dehydrogenation of cyclohexane into benzene was investigated by Itoh and Haraya. They found a higher conversion for the carbon membrane reactor comparing to the normal reactor, which was caused by the chemical reaction shifti ng to the product side due to the preferential permeation of H2. Sznejer and Sheintuch studied the dehydrogenation of isobutane to isobutene in a membrane reactor equipped... 

Decisive success in Sabatier s groundbreaking studies was reached at the end of 1900, with the conversion of benzene into cyclohexane upon treatment with hydrogen gas in the presence of nickel [25]. 

This reaction has the characteristics of a dead end polymerization, and the conversion of monomeric MMA to polymer can be controlled via the azo content of the polystyrene and the reaction temperature. The separation of the reaction products into homopolymer and block copolymer was achieved by selective solvent extraction thus, cyclohexane was used to dissolve the homopolystyrene, acetonitrile the homo-poly-MMA and the copolymer was completely soluble in benzene. The compositition of the crude product as a function of the ratio of MMA/prepolymer is shown in Fig. 4.5 58> ... 

The spiltover hydrogen can simply be added to benzene (forming cyclohexane and cyclohexene) in a noncatalytic reaction which exhausts entirely this hydrogen species, as shown below. Also, in order to have a clearcut picture, the reaction of benzene is carried out after evacuation of silica, which has been activated. The evacuation desorbs the spiltover hydrogen. Figure 17 shows the conversion at 170°C of benzene (8 cm3) with hydrogen (1000 cm3) into ethane and initially into acetylene (182). 

The differences in liquid product composition from the two types of processes are even more pronounced. The major liquid products (see Table V) from hydropyrolysis of 2 at 550°C are C6-Ci0 cyclohexenes and cyclohexanes, and C5-C8 open-chain hydrocarbons, while in thermal cracking the main liquid product at this temperature is 1,2,3,4,5,6,7,8-octahydronaphthalene. At 600°C a much higher conversion of 2 into C5—C10 aliphatic products is observed in the hydropyrolysis Experiment 25, whereas in the thermal cracking Experiment 26 there is much higher formation of aromatic products, i.e., benzene, toluene, ethylbenzene, and... 

The autoxidation of these materials depend on the polarity of the environment this is illustrated by the fact that the time taken for the conversion of 0.8% of linoleic acid into its hydroperoxide at 37° C. in cyclohexane, benzene, and 70 volume % aqueous ethyl alcohol was found to be 1, 2.5, and 20 days, respectively (22). 

The conversion of the sulfonyl chloride to the sulfonyl fluoride was carried out as follows. The sulfonyl chloride was removed from the filter by washing it with alcohol-free chloroform into a 5-ml round-bottom flask. The chloroform was then removed and 0.5 ml of acetonitrile and 167 mg of dry powdered sodium fluoride was added. The resulting mixture was magnetically stirred at 90°C for 6 hr, 2 ml of alcohol-free chloroform was then added and the mixture was filtered into a sublimation apparatus and the solvent was removed in a stream of nitrogen. The product sublimed readily at 45°C (0.3 mm) and could then be recrystallized from benzene-cyclohexane to yield crystals with m.p. 90-92°C. 

Bis(trifluoroacetoxy)iodo]benzene has also been used as a reagent for the Hofmann rearrangement, as illustrated by the conversion of amide 404 into the respective amine 405 (Scheme 3.162) [503], A similar [bis(trifluoroacetoxy)iodo]benzene-induced Hofmann rearrangement has been used for the preparation of both enantiomers of trfl 5 -2-aminocyclohexanecarboxylic acid from fran5-cyclohexane-l,2-dicarboxylic... 

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