Benzene from hexane

FIGURE 7.19 The reforming reaction that produces benzene from hexane uses a catalyst of platinum on alumina. The platinum facilitates the removal of hydrogen, and the alumina (AI2O3) facilitates the opening and closing of rings. One typical multistep sequence is shown other intermediates can form as well. 

Pt black, pulse system, carrier gas H2, T = 673 K. Averages of 4 or 5 runs, scattering 1 to 8%. After Ref. 46. Methylcyclopentane (MCP) and benzene were incompletely separated. MCP prevailed from 3-methylpentane and benzene from hexane. 

Methyllithium. MethyUithium [917-54 ] CH Li, crystallizes from benzene or hexane solution giving cubic crystals that have a salt-hke constitution (128). Crystalline methyllithium molecules exist as tetrahedral tetramers (129). Solutions of methyllithium are less reactive than those of its higher homologues. Methyllithium is stable for at least six months in diethyl ether at room temperature. A one-molar solution of methyllithium in tetrahydrofuran (14 wt %) and cumene (83 wt %) containing 0.08 M dimethyknagnesium as stabilizer loses only 0.008% of its activity per day at 15°C and is nonpyrophoric (117). 

Amino-4,6-dimethylpyridine [5407-87-4] M 122.2, m 69-70.5 , pK 7.84. Crystd from hexane, ether/pet ether or benzene. Residual benzene was removed over paraffin-wax chips in an evacuated desiccator. 

Di-tert-butyl-p-cresol (2,6-di-tert-butyl-4-methylphenol, butylatedhydroxytoluene, BHT) [128-37-0] M 230.4, m 71.5 , pK 12.23. Dissolved in n-hexane at room temperature, then cooled with rapid stirring, to -60°. The ppte was separated, redissolved in hexane, and the process was repeated until the mother liquor was no longer coloured. The final product was stored under N2 at 0° [Blanchard J Am Chem Soc 82 2014 7960]. Also crystd from EtOH, MeOH, benzene, n-hexane, methylcyclohexane or pet ether (b 60-80°), and dried under vacuum. 

Di-n-heptyloxyazoxybenzene [2635-26-9] M 426.6, m 75 , 95 (smectic nematic) and 127 (nematic - liquid), pK j —5. Purified by chromatography on AI2O3 (" benzene), recrystd from hexane or 95% EtOH and dried by heating under vacuum. The liquid crystals can be sublimed in vacuo. [Mellifiori et al. Spectrochim Acta Part A 37(A) 605 1981 Dewar and Schroeder J Am Chem Soc 86 5235 1964-, Weygand and Glaber J Prakt Chem 155 332 1940]. 

Dimethoxybenzene [150-78-7] M 137.2, m 57.2-57.8 . Steam distd. Crystd from hexane or benzene, and from MeOH or EtOH but these are wasteful due to high solubilities. Dried under vacuum. Also sublimes under vacuum. 

Dimethylphenol [576-26-1] M 122.2, m 49°, b 203°/760mm, pK 10.61. Fractionally distd under nitrogen, crystd from benzene or hexane, and sublimed at 38°/10mm. 

Crystd as its picrate (m 191°) from EtOH, then the free base was liberated, dried at 78°/8mm over P2O5 and crystd from pet ether (b 80-100°). [Cumper, Ginman and Vogel J Chem Soc 1188 1962.] It can be purified by zone melting. Also crystd from hexane, benzene/pet ether (b 40-60°) or sodium-dried benzene, dried and stored over H2SO4. The monohydrate is obtained by crystn from aqueous EtOH or ethyl acetate. It has been crystd from H2O (300 parts) to give the monohydrate m 102-103° and sublimes at lO mm [Fielding and LeFevre J... 

Pteridine [91-18-9] M 132.2, m 139.5-140°, pKj 4.05 (equilibrium, hydrate), pK 11,90 (OH of hydrate). Crystd from EtOH, benzene, n-hexane, n-heptane or pet ether. It sublimes at 120-130°/20mm. Stored at 0°, in the dark turns green in the presence of light and on long standing in the dark. 

Thenoyltrifluoroacetone [326-91-0] M 222.2, m 42-44°, b 96-98°/9mm. Crystd from hexane or benzene. (Aqueous solns slowly decompose). 

There are two process MSAs available to remove benzene from the wastewater streams. These process MSAs ate hexane (Si) and heptane (S2). Hexane is available at a flowrate of 0.8 kg/s and supply composition of 10 j mw while heptane is available at a flowrate... 

The precipitate was then mixed with diatomaceous earth, collected on a filter, and washed with water and extracted with two 100 ml portions of boiling benzene. The aqueous filtrate was extracted with 50 ml of benzene, the combined benzene extracts washed with water and evaporated to dryness under reduced pressure. The crystalline residue, MP 140° to 147°C, weighed 30.8 g. Recrystallization from a mixture of benzene and hexane gave 27.6 g (83%) of 2-chloro-10-(3-dimethylaminopropyl)-10-hydroxythiaxanthene, MP 152° to 154°C. Analytically pure material from another experiment melted at 153° to 154°C. 

The residue is triturated with methanol to afford a crystalline solid. This material contains no detectable amount of starting material by paperstrip chromatography but shows two UV absorbing spots near the solvent front (methanol-formamide 2 1 vs benzene-n-hexane 1 1). An aliquot is recrystallized three times from a mixture of benzene and n-hexane to give 17a,20,20,21-bis(methylenedioxy)-11(3-hydroxy-6,16a-dimethyl-4,6-pregnadiene-3-one which is used in the subsequent step of the synthesis without further purification. 

A solution of 27.2 parts of 4-diisopropvlamino-2-phenvl-2-(2-pvridvl)butyronitrile in 200 parts of concentrated sulfuric acid is heated on a steam bath for 4 hours and then poured onto ice. The resultant mixture is alkalized with ION sodium hydroxide, and the pH is adjusted to 6 by the addition of acetic acid. The solution is washed once with benzene before it is alkalized again with ION sodium hydroxide solution. The resultant mixture is extracted with benzene, and the solvent is evaporated from the benzene extract. The resultant residue is dissolved in ethanol and the alcohol solution is treated with charcoal and filtered. Evaporation of the solvent leaves a residue which is recrystallized from hexane to give 4-diisopropvlamino-2-phenvl-2-(2-Pvridvl)butyramide melting at about 94.5°-95°C. 

The excess thionyl chloride was removed under vacuum and by distilling from the residue two portions of dry benzene. The crystalline residue was crystallized twice from hexane-ether to yield 3,4,5-trimethoxycinnamoyl chloride which was obtained in the form of bright yellow prisms, MP 95° to 96°C. 

To a solution of thienyl magnesium bromide prepared from 21.4 g of magnesium and 144 g of 2-bromothiophene are added 39.B g of ethyl 4-dimethylaminocyclohexylcarboxylate. The mixture is ailowed to warm to room temperature and stirred for an additional six hours. The reaction mixture is then decomposed with dilute ammonium chloride solution and extracted with ether. The combined ether extracts are extracted thoroughiy with 10% hydrochloric acid and the acid solution made alkaline with ammonium hydroxide. The aqueous solution is extracted with chloroform which is then washed with water, dried and evaporated to a residue in vacuo. Recrystallization of the residue from hexane yields Oi.O -dithienyl-4-dimethyl-aminocyclohexyl carbinol, melting point 156°C to 157°C after recrystallization from benzene. 

Selectivity to benzene from reforming n-hexane over a platinum catalyst ... 

The yield increased with increasing the ratio of alumina-supported copper(II) bromide to alkoxybenzenes. The size of alkoxy group did not influence significantly the yield and the ratio of p/o. Nonpolar solvents such as benzene and hexane were better than polar solvent. Polar solvents such as chloroform and tetrahydrofiiran decreased the yield. It is suggested that these polar solvents may be strongly adsorbed on the surface of the reagent. The reaction did not proceed in ethanol to be due to the elution of copper(II) bromide from the alumina to the solution. It is known that the reaction of aromatic hydrocarbons with copper(II) halides in nonpolar solvents proceeds between aromatic hydrocarbons and solid copper(II) halides and not between hydrocarbons and dissolved copper(II) halides (ref. 6). 

A mixture of 1-methoxynaphtalene (0.95 g, 6 mmol) and alumina-supported copper(II) bromide (6 g) in benzene (30 ml) was stirred at 30°C for 1 h. The rnixmre was filtered and the spent reagent was washed several times with hot benzene. Hexane was added to the combined filtrates, which was concentrated, to precipitate 4,4 -dimethoxy-l,r-binaphtyl (0.82 g, 87 %), mp 254-255°C (from hexane-benzene (lit. 252-254°C (ref. 15)). 

Because Me3SiI (TIS) 17 is relatively expensive and very sensitive to light, air, and humidity, it is usually prepared in situ from TCS 14 and Nal in acetonitrile [1-6], although other solvents such as CH2CI2, DMF, benzene, or hexane have also been used [5, 6] (Scheme 12.1). It is assumed that TIS 17 forms, in situ, with MeCN, a (T-complex 1733 [2, 3-6], yet Me3SiI 17 can also be prepared by treatment of hex-amethyldisilane 857 with iodine in organic solvents [4-6]. The chemistry of TIS 17 has been reviewed [4—6]. 

Figure 1. l Sn nmr spectra of 10% w/v poly(TBTM/MMA) in several solvents. From the top chloroform, benzene, n-hexane, acetone, tetrahydrofuran, methanol, and pyridine. 

The mixture is treated with 35 ml. of water (Note 6) and stirred vigorously for a few minutes. The benzene layer is decanted, and the aqueous slurry is rinsed with two 125-ml. portions of benzene (Note 7). The combined organic extracts are washed once with 100 ml. of aqueous 5% sodium hydroxide (Note 8) and with 100 ml. of water, dried over anhydrous magnesium sulfate, and filtered. The solvent is removed by distillation under reduced pressure, preferably on a rotary evaporator, from a water bath kept at 30° (Note 9) to give 17.7-22.0 g. (76-94%) of /-butyl carbamate as white needles, m.p. 104-109° (Note 10). The product may be recrystallized from hexane (Note 11) m.p. 107-109° (Note 12). 

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