Cyclohexane, reactions

Aschmann, S. M., Chew, A.A., Arey, J., and Atkinson, R. Products of the gas-phase reaction of OH radicals with cyclohexane reactions of the cyclohexoxy radical, / PAys. Chem. A, 101(43) 8042-8048, 1997. 

Aschmann, S. M A. A. Chew, J. Arey, and R. Atkinson, Products of the Gas-Phase Reaction of OH Radicals with Cyclohexane Reactions of the Cyclohexoxy Radical, J. Phys. Chem. A., 101, 8042-8048 (f997a). 

TABLE 5 Deactivation of Singlet and Triplet Excited Linked Anthracenes. (Fluorescence Quantum Yields < >F in Cyclohexane. Reaction Quantum Yields < >R in Benzene)... 

Reactions peifomied in cyclohexane at 70 X . Reaction perfonncd at 70-80 in cyclohexane. Reaction performed at 60 C in cyclohexane. Rewtions performed in chlorabenzm at 85 °C for 6-8 h using 4 equiv. Bu OOH and 4 mol % of Ci -impregnated NAFK. 

The dehydrogenation of hexane to hexene or cyclohexane (reactions 5 and 6) only becomes appreciable at temperatures approaching 800 °K. The dehydrogenation to methylcyclopentane however appears to be thermodynamically feasible at temperatures as low as 350 °K. One cannot place too much reliance on this particular result since the affinity of formation of methylcyclopentane is known less accurately than the others. These three reactions, however, scarcely affect the synthesis of aromatic compounds in the reaction since the ethylenes and cycloparaffins are thermodynamically unstable relative to aromatic hydrocarbons above 550 °K, and they decompose spontaneously to form aromatics at this temperature. They can therefore only appear as intermediates in reaction (9) above 550 °K. 

In the ideal form of this structure, only (100) and (111) planes occur, but atoms are also situated at sites corresponding to corners and at edges between these planes. These have lower coordination than plane sites and exhibit different orbital symmetries. The distribution of these sites is shown in Fig. 4.U. suggesting that adsorption and reaction involving low coordina tion sites increases as crystallite size decreases, whereas those occurring on face sites increase with size. Thus a crystallite size effect is seen, as verified by experiments on selectivity factors in cyclohexane reactions... 

RCO 2 undergoes a fast decarboxylation (reaction (2)) [40]. R can react either according to reaction (3) or transfer H from the cyclohexane (reaction (9)). The competition between the two reactions depends on the structure of R Due to the low nucleophilic character of the norbonyl-1 radical, reaction (3) is slow (vide... 

Oxidation of cyclohexanol was carried out at 328 K in a three necked round bottomed flask under reflux conditions using 30 wt.% H2O2 as oxidant and acetone as solvent. The temperature was maintained by thermostated oil bath. For oxidation of cyclohexane, reaction was performed in a PARR (4842) autoclave at 423 K for 3h. Quantitative analysis of the products were done using Nucon G.C. fitted with a FID. 

Higher homologs of cyclopentane are converted more readily, but it is important to note that there is a fundamental difference between cyclohexane reactions and those of all other hydrocarbon types. The aromatization of cyclohexane is largely a function of the platinum component. The acid function will, in fact, promote side reactions unless conditions are controlled carefully. In the case of methylcyclopentanes (or paraffins) the extent of conversion is a function of the catalyst halogen content (i.e., the acidity) and depends on the platinum content only up to a very low critical level of platinum. 

Benzene is the raw material for the two most important routes for the manufacture of polymers that are collectively referred to as Nylon. In the first route, cyclohexane is oxidised to adipic acid (HOOC—(CH2)4—COOH), and for this reason the full hydrogenation of benzene has commanded much attention. Because of the large heat of reaction, the process is best performed in the slurry phase, using an unsupported catalyst such as Raney nickel the process heat is removed by vaporisation of the cyclohexane, part of which is returned to the feed, which typically contains 20% benzene -f- 80% cyclohexane. Reaction conditions are 30-50 atm. hydrogen and temperatures of 453-503 K. In the second route, the starting compound is cyclohexene, and for some time efforts have been made to effect the partial hydrogenation of benzene to this molecule (see Section 10.2.7). 

Ring closure probably occurs through cyclohexadiene , but the elucidation of the exact mechanism of ring closure needs further isotope studies. The initial steps, that is the dissociative adsorption in the dehydrogenation of cyclohexane and in the D/H exchange reactions taking place between cyclohexane and deuterium on metal surfaces, are similar Cyclohexane, cyclohexene and benzene have been found to contain tritium activity when a catalyst covered with tritium has been used in the dehydrocyclization experiments. No hexane —> cyclohexane reaction occurs. 

Wolfgang and his coworker (Menzinger and Wolfgang 1969) studied threshold energy of substitution products in T -i-C6Hi2 (solid cyclohexane) reaction using a tritium beam accelerator. For simple substitution, the threshold energy is about 0.5 eV. However, for the products (n-hexane-T and hexane-T) for which C-C bond rupture is required, it is about 4.5 eV. 

---