Cyclohexane Friedel-Crafts reaction

Extensive investigations of the Friedel-Crafts reaction between cycloalkanes and acetyl chloride have been reported by Zelinsky and Tarassowa 620 they found that, according to the reaction conditions, either saturated or unsaturated ketones were formed and that cyclohexane derivatives may rearrange to methylcyclopentane derivatives (cf. Nenitzescu and Hopff621-623). 

Friedel-Crafts reaction can proceed in a rather limited number of inert solvents, such as aliphatic hydrocarbons, benzene, nitrobenzene, CS2, and chlorinated or fluorinated hydrocarbons. Among these solvents, however, only chlorinated hydrocarbons, particularly EDC, nitrobenzene, as well as cyclohexane at an elevated temperature, are suited for the synthesis of hypercrosslinked polystyrene, since they are thermodynamically good solvents for both the initial polystyrene and the final products of crosslinking. 

One outstanding reaction related to Friedel-Crafts alkylation is the sliding cyclohexane rearrangement mediated by ZrCU as shown in Eq. (13) [14]. When tetralin 29 was stirred with ZrCU at ambient temperature for 2 days isomerized product 32 was obtained in high yield. The mechanism in which intermediates 30 and 31 are proposed involves the ambivalent, hard and soft Lewis acidic character of zirconium. 

When cyclohexyl chloride is the desired product for use in the preparation of cyclohexylamine or for condensations according to the Friedel and Crafts reaction, it appears advantageous to chlorinate in the presence of light and to use at least a 10 1 molar ratio of cyclohexane to chlorine in a cyclic process. The products of reaction are continuously withdrawn from the reaction chamber to a still (Fig. 6-6) where the unconverted cyclohexane is distilled off, condensed, and returned to the chlorinator which is provided with an encased battery of electric lights. The chlorinator, which is maintained at 65-65°C, is preferably made of lead, nickel, or Monel metaJ in order to provide better resistance against the corrosive action of the reaction products. A 5deld of about 94 per cent cyclohexyl chloride is thus obtained in batch operations when about half of the chlorine theoretically required to convert all the cyclohexane to cyclohexyl chloride has been reacted. 

As already mentioned in Chapter 6, Section 4, appropriate solvents for conducting Friedel—Crafts crosslinking reaction of polystyrene are EDC, tetrachloroethane, nitrobenzene, and cyclohexane (at an elevated temperature). While the products prepared in the first two solvents are identical in aU their swelling behavior, the character of swelling of materials obtained in nitrobenzene is different. 

One example (36) describes Co-TUD-1 for liquid-phase oxidation of cyclohexane. Another example (37) describes the synthesis, characterization, and catalytic performance of Fe-TUD-1 for Friedel-Crafts benzylation of benzene. Other reactions were described ... 

Problem 13.— Explain exactly how the Friedel and Crafts Reaction may be applied in the laboratory in order to (a) differentiate cyclohexane from benzene, and (6) benzyl chloride from o-chlorotoluene. 

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