Cyclohexanol from phenol

Figure 12.14 Chromatographic analysis of aniline (a) Precolumn chromatogram (the compound represented by the shaded peak is solvent flushed) (b) main column chromatogram without cryotrapping (c) main column chromatogram with ciyottapping. Conditions DCS, two columns and two ovens, with and without ciyottapping facilities columns OV-17 (25 m X 0.32 mm i.d., 1.0 p.m d.f.) and HP-1 (50 m X 0.32 mm, 1.05 p.m df). Peak identification is as follows 1, benzene 2, cyclohexane 3, cyclohexylamine 4, cyclohexanol 5, phenol 6, aniline 7, toluidine 8, nittobenzene 9, dicyclohexylamine. Reprinted with permission from Ref. (20).

The common name caprolactam comes from the original name for the Ce carboxylic acid, caproic acid. Caprolactam is the cyclic amide (lactam) of 6-aminocaproic acid. Its manufacture is from cyclohexanone, made usually from cyclohexane (58%), but also available from phenol (42%). Some of the cyclohexanol in cyclohexanone/cyclohexanol mixtures can be converted to cyclohexanone by a ZnO catalyst at 400°C. Then the cyclohexanone is converted into the oxime with hydroxylamine. The oxime undergoes a very famous acid-catalyzed reaction called the Beckmann rearrangement to give caprolactam. Sulfuric acid at 100-120°C is common but phosphoric acid is also used, since after treatment with ammonia the by-product becomes... 

Adipic acid may be obtained from cyclohexanol by oxidation with hot nitric acid. Cyclohexanol is prepared from phenol by hydrogenation. Thus the entire series of reactions represents (a) the change of an aromatic six-carbon compound to an alicyclic one (6) the opening of a six-carbon ring to an open chain compound (c) the cyclization of an open chain compound. The object of the present experiment is to illustrate this last step through the preparation of cyclopentanone from adipic acid. 

This graph gives a selection of 14 (out of approx. 360) usual solvents above the basis line and 7 exotic solvents (ionic liquids included) below. The 14 compounds include (from left to the right increasing solvent polarity) apolar, aprotic solvents (such as TMS, cyclohexene, or benzene), bipolar solvents (such as acetone, DMF, or DMSO), and eventually bipolar, protic solvents (cyclohexanol, ethanol, phenol, 2,2,2-trifluoroethanol). Using the Ej values numerous solvent-dependent processes may be correlated by far better than with the physical values of the solvents alone. This is true because the Ej values include specific cross interactions as well. 

Although outside the scope of the present chapter, another transformation of interest is the conversion of the fully hydrogenated product from phenol, namely cyclohexanol, to cyclohexanone in 100% yield by addition of a dichloromethane solution to bis(quinuclidine)bromine fluoroborate and silver fluoroborate in dichloromethane followed by reaction for 30 mins.at ambient temperature (ref.65). 

Another way of explaining this difference in acidity is to say that the activation energy (the energy differential between the reactants and the transition state of the reaction) for phenol s ionization is less than that of cyclohexanol s loss of a proton. NaOH is a base that will receive a proton from phenol but not from the weaker acid cyclohexanol. Experimentally, this means that the phenoxide salt will be in the aqueous layer of an ethereal-aqueous mixture and will easily be removed. Subsequent protonation will yield phenol. 

The introduction of electronegative substituents into the benzene ring increases the reactivity thus phenol is hydrogenated to cyclohexanol in satisfactory yield at a platinized Pt cathode in aqueous acidic media. In the gas phase, Coussemant has reported cyclohexanone formation from phenol. 

The loss of the hydroxyl group from either the starting cyclohexanol (to give cyclohexane), or from phenol (to give benzene) can also take place. Dehydration of cyclohexanol to cyclohexene is also possible as summarised in Scheme 3. These reactions were studied over various metal catalysts, by using different mixtures containing one labelled component. Typical results obtained on Cu, Ni and Pt catalysts are summarised in Table 5. The specific radioactivities decreased in the sequence cH-ol > cH-one > phenol on Cu and Ni catalysts, while a different order cH-ol > phenol > cH-one was observed on Pt, as well as on Pd. Thus, the sequential reaction 1 2 leads to phenol in the former two catalysts and the direct route to phenol lA is possible on Pt and Pd. The following relative rates were determined for Ni catalyst ... 

The main products of this process are benzene, cyclohexane, and cyclohexane. The benzene was formed by direct hydrogenolysis from phenol, while the cyclic hydrocarbons were formed by hydrogenation of phenol via the intermediate cyclohexanol and cyclohexanone. 

In the synthesis of adipic acid one can start with benzene, phenol, tetrahydrofuran, butadiene, or cyclohexane. Benzene is converted to phenol (e.g., by the cumene process), this is hydrogenated to cyclohexanol, and the cyclohexanone gained by oxidation is then oxidized to adipic acid, HOOC—(CH2)4—COOH, with nitric acid. Cyclohexane can also be oxidized with air to cyclohexanol, from which adipic acid is obtained by direct nitric acid oxidation. Adipic acid can also be produced by saponification of adipodinitrile (adiponitrile), which in turn comes from tetrahydrofuran or butadiene (see below). 

Cyclohexanol and cyclohexanone are produced from phenol as intermediates for synthetic fibers (Nylon 66, Nylon 6) obtained via adipic acid and caprolactam respectively. 

The original preparation of cyclohexanone from phenol by hydrogenation to cyclohexanol followed by dehydrogenation has since been improved. Selective hydrogenation of phenol to cyclohexanone is possible using a palladium catalyst at 140°-170°C and 1-2 atm. An AlliedA ickers-Zimmer catalyst contained 0.5-5% palladium, supported on a low-surface-area calciiun aluminate which contained about 8-9% calcium oxide. ... 

Phenol Vi Cyclohexene. In 1989 Mitsui Petrochemicals developed a process in which phenol was produced from cyclohexene. In this process, benzene is partially hydrogenated to cyclohexene in the presence of water and a mthenium-containing catalyst. The cyclohexene then reacts with water to form cyclohexanol or oxygen to form cyclohexanone. The cyclohexanol or cyclohexanone is then dehydrogenated to phenol. No phenol plants have been built employing this process. 

Riboflavin forms fine yellow to orange-yeUow needles with a bitter taste from 2 N acetic acid, alcohol, water, or pyridine. It melts with decomposition at 278—279°C (darkens at ca 240°C). The solubihty of riboflavin in water is 10—13 mg/100 mL at 25—27.5°C, and in absolute ethanol 4.5 mg/100 mL at 27.5°C it is slightly soluble in amyl alcohol, cyclohexanol, benzyl alcohol, amyl acetate, and phenol, but insoluble in ether, chloroform, acetone, and benzene. It is very soluble in dilute alkah, but these solutions are unstable. Various polymorphic crystalline forms of riboflavin exhibit variations in physical properties. In aqueous nicotinamide solution at pH 5, solubihty increases from 0.1 to 2.5% as the nicotinamide concentration increases from 5 to 50% (9). 

Me3SiCH2CH=CH2i TsOH, CH3CN, 70-80°, 1-2 h, 90-95% yield. This silylating reagent is stable to moisture. Allylsilanes can be used to protect alcohols, phenols, and carboxylic acids there is no reaction with thiophenol except when CF3S03H is used as a catalyst. The method is also applicable to the formation of r-butyldimethylsilyl derivatives the silyl ether of cyclohexanol was prepared in 95% yield from allyl-/-butyldi-methylsilane. Iodine, bromine, trimethylsilyl bromide, and trimethylsilyl iodide have also been used as catalysts. Nafion-H has been shown to be an effective catalyst. 

A route to phenol has been developed starting from cyclohexane, which is first oxidised to a mixture of cyclohexanol and cyclohexanone. In one process the oxidation is carried out in the liquid phase using cobalt naphthenate as catalyst. The cyclohexanone present may be converted to cyclohexanol, in this case the desired intermediate, by catalytic hydrogenation. The cyclohexanol is converted to phenol by a catalytic process using selenium or with palladium on charcoal. The hydrogen produced in this process may be used in the conversion of cyclohexanone to cyclohexanol. It also may be used in the conversion of benzene to cyclohexane in processes where benzene is used as the precursor of the cyclohexane. 

Fig. 7. Dependence of relative molar concentrations n-Jn of reaction components on reciprocal space velocity W/F (hr kg mole-1) in the consecutive hydrogenation of phenol. Temperature 150°C, catalyst Pt-SiCh (1% wt. Pt), initial molar ratio of reactants G = 9. The curves were calculated (1—phenol, 2—cyclohexanone, 3—cyclohexanol) the points are experimental values. From Ref. (61). Reproduced by permission of the copyright owner.

The photoinitiator selected for this study was 1-benzoyl cyclohexanol (Irgacure 184 from Ciba Geigy), a compound known for its high initiation efficiency and the weak coloration of its photoproducts. The multifunctional monomer was an epoxy-diacrylate derivative of bis-phenol A (Ebecryl 605 from UCB). A reactive diluent, tripropyleneglycol diacrylate, had to be introduced in equal amounts, in order to lower the viscosity of the formulation to about 0.3 Pa.s. 

The reaction product was filtered to remove catalyst and analyzed in GC equipped with an HP5 (30 m X 0.32 mm X 0.25 pm) column. The temperature program used for analysis (31 °C - 35 min - 1 °C/min - 40 °C - 10 °C/min -120 °C) ensured complete separation of the cyclohexanol, cyclohexanone, and phenol peaks. The conversion and selectivity were calculated directly from the area of each peak. 

Halcon (1) Halcon International (later The Halcon SD Group) designed many organic chemical processes, but is perhaps best known for its process for making phenol from cyclohexane. Cyclohexane is first oxidized to cyclohexanol, using air as the oxidant and boric acid as the catalyst, and this is then dehydrogenated to phenol. Invented in 1961 by S. N. Fox and J. W. Colton, it was operated by Monsanto in Australia for several years. 

The formation of certain ethers can also be accomplished with hydrogen fluoride. Anisole rather than methylphenol results from a reaction between phenol and methyl alcohol at elevated temperature (Simons and Passino, 40). The addition of an olefin to an alcohol to form an ether was shown to occur in the reaction between cyclohexene and cyclohexanol for form dicyclohexyl ether (Simons and Meunier, 66). 

Although there are measured enthalpies of formation of phenyl and cyclohexyl benzoylperoxycarbonate, there are none for the corresponding deoxygenated benzoylcarbonates that replace the —OO- moiety by —0-. The difference between the gas phase enthalpies of formation of the peroxy compounds, ca 258 13 klmol", is the hydrogenation enthalpy of the phenyl compound. This value is far in excess of the hydrogenation enthalpy of any other phenylated species from the enthalpies of formation of gaseous phenol and cyclohexanol, the difference is but 189.98 2.3 kJmol. ... 

Chemicals and Standard Solutions. Cyclohexanone, cyclohexanol, 1,3,5-trichlorobenzene, 1,2,4-trichlorobenzene, phenol, 4-methylphenol, 4-chloro-phenol, 1,2,3,4-tetrahydroisoquinoline, 1-chlorohexane, 1-chlorododecane, and 1-chlorooctadecane were obtained from Aldrich. Acetone, tetrahydrofuran, ethyl acetate, toluene, dimethyl sulfoxide, and methanol were obtained from J. T. Baker. Distilled-in-glass isooctane, methylene chloride, ethyl ether, and pentane were obtained from Burdick and Jackson. Analytical standard kits from Analabs provided methyl ethyl ketone, isopropyl alcohol, ethanol, methyl isobutyl ketone, tetrachloroethylene, dodecane, dimethylformamide, 1,2-dichlorobenzene, 1-octanol, nitrobenzene, 2,4-dichlorophenol, and 2,5-dichlorophenol. All chemicals obtained from the vendors were of the highest purity available and were used without further purification. High-purity water... 

Caprolactam [105-60-2] (2-oxohexamethylenimine, hexahydro-2.fi-azepin-2-one) is one of the most widely used chemical intermediates. However, almost all of the annual production of 3.0 x 106 t is consumed as the monomer for nylon-6 fibers and plastics (see Fibers survey Polyamides, plastics). Cyclohexanone, which is the most common organic precursor of caprolactam, is made from benzene by either phenol hydrogenation or cyclohexane oxidation (see Cyclohexanol AND cyclohexanone). Reaction with ammonia-derived hydroxylamine forms cyclohexanone oxime, which undergoes molecular rearrangement to the seven-membered ring 8-caprolactam. 

Zeolite catalysts in many forms are used for important commercial processes. The studies were extended to L zeolites, mordenite, erionite, and dealuminated faujasites and mordenites. More attention is paid now to zeolites with univalent and multivalent cations and to multicomponent catalysts. Among these some important examples are the tellurium-containing catalyst for hydrocarbon dehydrocyclization (42), the difunctional Ni- and Pd-zeolite catalysts for benzene hydrodimerization to phenylcyclohexane (42), the catalyst for the hydrogenation of phenol cyclohexanol (44), the 4% Ni/NaY which forms butanol, 2-ethylhexanol, 2-ethylhexanal, and 2-ethylhexanol from a mixture of n-butyraldehyde and hydrogen. 

Of special interest for petrochemical and organic synthesis is the implementation of thermodynamically hindered reactions, among which incomplete benzene hydrogenation or incomplete cyclohexene and cyclohexadiene dehydrogenation should be mentioned. Cost-effective methods of cyclohexene production would stimulate the creation of new processes of phenol, cyclohexanol, cyclohexene oxide, pyrocatechol synthesis, cyclohexadiene application in synthetic rubber production, and a possibility for designing caprolactam synthesis from cyclohexene and cyclohexadiene via combined epoxidation. At present, the most... 

Caprolactam is usually manufactured from cyclohexanone, made by the oxidation of cyclohexane or by the hydrogenation/oxidation of phenol (Fig. 1), although the manufacture can be an integrated process with several starting materials (Fig. 2). The cyclohexanol that is also produced with the cyclohexanone can be converted to cyclohexanone by a zinc oxide (ZnO) catalyst at 400°C. The cyclohexanone is converted into the oxime with hydroxylamine, which then undergoes rearrangement to give caprolactam. 

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