Acetone from pentane

Fig. 36. Distillation column to remove acetone from pentane.

The formation of large yields of acetone from n-pentane, however, has led to the suggestion that decomposition analogous to that of the of-dihydroperoxides is important... 

A solution of 9.3 g (0.03 mol) of triphenyl phosphite in 100 mL of dichloro-methane is ozonized to form triphenyl phosphite ozonide. After the excess ozone is purged with nitrogen, a cold solution of 1.60 g (0.02 mol) of 1,3-cyclohexadiene in 45 mL of dichloromethane is added from a dropping funnel while the mixture is stirred by a stream of nitrogen and cooled with a dry-ice-acetone bath. After the removal of the bath, the mixture is allowed to warm to room temperature. The solution is concentrated on a rotary evaporator, and the residue is distilled at less than 0.1 mm of Hg in a short-path still to give 1.51 g (67.4%) of pale-yellow semisolid 3,6-endooxocyclohexene, which, after three recrystallizations from pentane, melts at 90-91 °C. 

Aside from being immiscible with the pentane, the solvent, water, has to effect a reasonably different distribution of the species to be separated, methanol and/or acetone and pentane. 

We use rigorous simulation to determine feasible separations using water as a solvent. For a theoretical ten-stage liquid/liquid extraction process, we find that rather little water is needed to recover virtually all methanol from the pentane. At higher solvent flowrates the water-rich extract contains more and more acetone, but it cannot produce a complete separation of acetone and pentane. Thus, we select the solvent flow at which the methanol-pentane separation is sufficiently sharp. Figure 35 gives the separation selected. 

The obtained polyhydroxyoligosilanes are relatively thermally stable, colorless solids that can be purified by crystallization or precipitation from pentane or acetone, except for the liquid silanol 3a, which was purified by distillation under vacuum. The NMR spectra of the compounds are rather straightforward and are in full agreement with the structures proposed. 

By Photorearrangement of Iminoether 13 8-Methoxy-7-azabicyclo[4.2.2]deca-2,4,7,9-tetraene (13,2.4 g, 0.015 mol) was dissolved in reagent grade acetone (500 mL) and this solution was irradiated through a Pyrex filter sleeve as above. After 8 h, the solvent was evaporated in vacuo, and the resulting yellowish oil was dissolved in hexane (50-75 mL) and clarified by filtration through neutral alumina. Concentration afforded a colorless oil which was crystallized from pentane to give the product yield 2.1 g (88%) as white crystals, mp 49.5-50.5 C, identical in all respects with the sample from lactam 12. 

Crystals from pentane, mp 114-116. Vapor pressure at 100 3.75 X 10-3 mm Hg. Sol in ethanol aud acetone. Very slightly sol in water- LDM orally in rats 1040 mg/kg (Bailey. White). One of the ingredients of Banfene and of Cambilene. 

O-Acetylholarrhenine, C26H42N202, crystals from pentane or acetone, mp 177-178. ... 

Cassamine crystallizes from pentane and then melts at 86-87° with [a]p —56° (ethanol). The perchlorate crystallizes from dilute acetone, the bisulfate from ethanol-ether, and the hydrochloride from acetone, but the salts do not have sharp melting points. The hydrobromide and the picrate were obtained in the amorphous state. When heated with 2N hydrochloric acid cassamine generates dimethylaminoethanol and cassamic acid, CaiHsoOe, (m.p. 217-218°, [a]D —62° in ethanol). This acid yielded a noncrystalline methyl ester which formed a crystalline p-nitrophenyl-hydrazone (m.p. 227-228") and an oxime (m.p. 96-98°). The p-phenyl-phenacyl ester of cassamic acid crystallizes readily and melts at 127-131°. One methoxyl and a double bond conjugated with the carboxyl are present in the acid, so that the function of only one oxygen remains to be determined. 

Deriv Methyl epiphorellate I, mp 135-137 °C (acetone-n-pentane), from epiphorellic acid I with CH2N2... 

When the Knoevenagel condensates (3), prepared from pentane-2,4-dione and aldehydes, are reduced with tetracarbonylhydridoferrate, [FeH(CO)4], in ethanol, the unexpected monoketones (5) are produced in 70% yield, whereas in acetone or THF the expected reduction product (4) is formed in good yield. 

Hydroxyacetanilide. This derivative (21), also known as 4-acetamidophenol, acetaminophen, or paracetamol, forms large white monoclinic prisms from water. The compound is odorless and has a bitter taste. 4-Hydroxyacetani1 ide is insoluble in petroleum ether, pentane, and ben2ene slightly soluble in diethyl ether and cold water and soluble in hot water, alcohols, dimethylformamide, 1,2-dichloroethane, acetone, and ethyl acetate. The dissociation constant, pfC, is 9.5 (25°C). 

Methyl-l-butanol [137-32-6 RS 34713-94-5 S(-)- 1565-80-6] M 88.2, b 130°(/ S), 128.6°(S), [a]p -5.8° (neat), d 0.809, n 1.4082. Refluxed with CaO, distd, refluxed with magnesium and again fractionally distd. A small sample of highly purified material was obtained by fractional crystn after conversion into a suitable ester such as the trinitrophthalate or the 3-nitrophthalate. The latter was converted to the cinchonine salt in acetone and recrystd from CHCI3 by adding pentane. The salt was saponified, extracted with ether, and fractionally distd. [Terry et al. J Chem Eng Data 5 403 7960.]... 

The general purification methods listed for xylene are applicable. p-Xylene can readily be separated from its isomers by crystn from such solvents as MeOH, EtOH, isopropanol, acetone, butanone, toluene, pentane or pentene. It can be further purified by fractional crystn by partial freezing, and stored over sodium wire or molecular sieves Linde type 4A. [Stokes and French J Chem Soc, Faraday Trans 1 76 537 1980.]... 

Reprecipitation from acetone/pentane is repeatedly effected until the condensation product suits in flaky form. Further purification is effected in that the crude product is chromatographed on silica gel. The fractions which are uniform in accordance with thin layer chromatography are combined and yield crystals from absolute alcohol. Pure 4 -demethylepipo-dophyllotoxin-/3-D-thenylidene glucoside has a melting point of 242°C to 246°C (last residue up to 255°C). 

To a solution of 1.30 g (5.5 mmol) of (-)-sparteine in 20 mL of pentane and 2.5 mL of cyclohexane are sequentially added dropwise between —78, C and -70 C 5.5 mmol of an approx. 1.5 M solution of sec-butyllithium in 2-methylbutane/cyclohexane and 5.0 mmol of the 2-alkenyl diisopropylcarbamate in 5 mL of pentane. After 10 min stirring, the flask is raised from the dry-ice/acetone bath and cautiously shaken to remove the precipitate from the glass wall of the flask. The temperature must not rise above — 50 CC. After chilling the flask again to —70 °C, shaking of the flask is repealed and stirring is continued below — 70 C overnight. 

Purely parallel reactions are e.g. competitive reactions which are frequently carried out purposefully, with the aim of estimating relative reactivities of reactants these will be discussed elsewhere (Section IV.E). Several kinetic studies have been made of noncompetitive parallel reactions. The examples may be parallel formation of benzene and methylcyclo-pentane by simultaneous dehydrogenation and isomerization of cyclohexane on rhenium-paladium or on platinum catalysts on suitable supports (88, 89), parallel formation of mesityl oxide, acetone, and phorone from diacetone alcohol on an acidic ion exchanger (41), disproportionation of amines on alumina, accompanied by olefin-forming elimination (20), dehydrogenation of butane coupled with hydrogenation of ethylene or propylene on a chromia-alumina catalyst (24), or parallel formation of ethyl-, methylethyl-, and vinylethylbenzene from diethylbenzene on faujasite (89a). 

Figure 14.1 Vapor-liquid equilibrium data and calcidated values for the n-pentane-acetone system, x andy are the mole fractions in the liquid and vapor phase respectively [reproduced with permission from Canadian Journal of Chemical Engineering].

Crystallized from acetone/pentane. Bond to three-coordinate thallium. f Bond to four-coordinate thallium. 

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