Mixtures acetic acid + «-butane + water

Although acetic acid and water are not beheved to form an azeotrope, acetic acid is hard to separate from aqueous mixtures. Because a number of common hydrocarbons such as heptane or isooctane form azeotropes with formic acid, one of these hydrocarbons can be added to the reactor oxidate permitting separation of formic acid. Water is decanted in a separator from the condensate. Much greater quantities of formic acid are produced from naphtha than from butane, hence formic acid recovery is more extensive in such plants. Through judicious recycling of the less desirable oxygenates, nearly all major impurities can be oxidized to acetic acid. Final acetic acid purification follows much the same treatments as are used in acetaldehyde oxidation. Acid quahty equivalent to the best analytical grade can be produced in tank car quantities without difficulties. 

Materials Required Silica gel-G mobile-phase (glacial acetic acid water butan-l-ol 20 20 20 60) 100 ml solution (1) dissolve 0.1 g of sample in 5 ml of 2 M ammonia solution (2) dilute 1 ml of soln. (1) to 50 ml with water solution (3) dilute 5 ml of solution (2) to 20 ml with water Solution (4) dissolve 10 mg of glutamic acid EPCRS in sufficient water to produce 50 ml solution (5) dissolve 10 mg of glutamic acid EPCRS and 10 mg of aspartic acid EPCRS in sufficient water to produce 25 ml ninhydrin solution (0.2% w/v solution of ninhydrin in a mixture of 95 vols. of butan-l-ol and 5 vols of 2 M acetic acid ) 50 ml ... 

Suspend the purified salt in 850 ml of water in a stoppered bottle, add 25 ml of pure pyridine and shake the mixture for 4-5 hours. Remove the insoluble pyridine rhodanilate by filtration and wash it with 100 ml of cold water (2). Combine the pale pink filtrate and washings, and add glacial acetic acid dropwise until the formation of a small pink precipitate is complete. Filter, evaporate the almost colourless filtrate to dryness (rotary evaporator) and suspend the residue in absolute ethanol and re-evaporate twice. Dry the resulting faintly pink crude proline in a vacuum desiccator over silica gel the yield is about 18 g. Recrystallise from the minimum volume of absolute ethanol to obtain 11 g (7.3% based on gelatin) of L-proline, m.p. 218-219 °C (decomp.), [oc]d8 —85.6° (c3.0 in H20). Check the purity of the product by t.l.c. on silica gel using the solvent system butan-l-ol-acetic acid-water, 4 1 1 Rf 0.26 (yellow spot with ninhydrin). 

For polar organic substances more soluble in water than in organic liquids, there will be little movement if an anhydrous mobile phase is used adding water to the solvent will cause those substances to migrate. Thus, butan-1-ol is not a suitable solvent for amino acids unless it is saturated with water addition of acetic acid allows more water to be incorporated, and hence increases the solubility of amino acids, particularly basic ones the addition of ammonia increases the solubility of acidic materials. tert-Butanol and water mixtures are the primary solvent for the separation of many polar anionic species, and many other polar substances with solubility characteristics similar to those of amino acids, such as indoles, guanidines and phenols, can be separated with this mixture. For hydrophobic stationary phases, various mixtures of benzene, cyclohexane and chloroform have been used to good effect as eluants. 

Several solvent systems have been proposed for PC such as butan-l-ol/acetic acid/water, butan-l-ol/ ammonia/watei butanol-l-of/water, ethanol/ammonium acetate, and methanol/formic acid/water. Generally, the separation of a complex mixture of bases, nucleosides, and nucleotides requires using successively two solvent systems for two-dimensional PC. Since Rp values may vary slightly with chromatographic conditions, it is recommended that identifications be checked by comparing the Rp values of the mixture components with those of authentic samples in several solvent systems. 

Thiamin may be extracted from tissues, foodstuffs or pharmaceutical preparations with aqueous alcohol mixtures at a pH of 4-6 and separated from closely related compounds and metabolites by TLC on cellulose layers or silica gel. Various mobile phases have been used, including isopropanol-water-trichloracetic acid-ammonia (71 9 20 0.3) and butan-l-ol-acetic acid-water (40 10 50) (1). Thiamin may be separated from its hydrolysis and oxidation products by TLC/densitometry (2) and other chromatographic techniques have been reviewed (3). Sandwich-type chambers afford rapid... 

Tetraethyl butane-1,1,4,4-tetrtacarboxylate added to a soln. of Na in abs. alcohol, to the resulting soln. tetraethyl l,4-dibromobutane-l,l,4,4-tetracarboxy-late added, and heated 4 hrs. in an oil bath at no-IIS -> tetraethyl cyclobutane-1,1,2,2-tetracarboxylate (Y 75.2%) boiled with aq. HGl (1 1) at ISO-HO in an oil bath until the oily layer has dissolved after 35-40 hrs., the HGl removed by distillation, and the residue heated at 180-200° until G0.2-evolution ceases mixture of cis- and frans-cyclobutane-l,2-dicarboxylic acids (Y 97.5%) refluxed 5 hrs. at 70-90° with acetjd chloride on a water bath, excess acetyl chloride and the resulting acetic acid removed by distillation at atmospheric pressure, and the residue heated 6-7 hrs. at 160-175° in an oil bath whereby the mixed anhydride of frans-cyclobutane-l,2-dicarboxylic acid and acetic acid is converted to acetic anhydride and cis-cyclobutane-l,2-dicarboxylic acid anhydride (Y 81.2%) boiled with 2 parts of water cis-cyclobutane-l,2-di-carboxylic acid (Y ca. 100%). V. P. Gol mov and Z. P. Malevannya, 7K. 31, 665 (1961) G. A. 55, 22162b method of ring closure s. J. J. Lennon and W. H. Perkin, Soc. 1928, 1513. 

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