Water acetic acid, chloroform

Type and composition of the mobile phase (usually constituted by ternary organic or aqueous organic mixtures such as -butanol/acetic acid/chloroform and acet-onitrile/methanol/water) play a role as well. Even binary and quaternary mixtures, consisting of acetonitrile/methanol and -butanol/acetic acid/chloroform/water, were used with various proportions. 

If the amine is soluble in water, mix it with a slight excess (about 25 per cent.) of a saturated solution of picric acid in water (the solubility in cold water is about 1 per cent.). If the amine is insoluble in water, dissolve it by the addition of 2-3 drops of dilute hydrochloric acid (1 1) for each 2-3 ml. of water, then add a sUght excess of the reagent. If a heavy precipitate does not form immediately after the addition of the picric acid solution, allow the mixture to stand for some time and then shake vigorously. Filter off the precipitated picrate and recrystaUise it from boiling water, alcohol or dilute alcohol, boiUng 10 per cent, acetic acid, chloroform or, best, benzene. 

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). 

Analysis calculated for C1SH36N2O4S C, 57.41 H, 9.63 N, 7.43 S, 8.51. Found C, 57.60 H, 9.66 N, 7.37 S, 8.25. Thin-layer chromatograms (Note 10) run by the submitters showed a single spot for the product in each of three following solvent systems (solvents, volume ratio of solvents in the same order) chloroform-methanol-acetic acid, 85 10 5, Rf 0.60 1-butanol-acetic acid-water, 4 1 1, Rf 0.58 l-butanol acetic acid-pyridine-water, 15 3 10 12, Rf 0.71. 

Active oxygen content is determined iodometrically 3 In an iodine flask, an accurately weighed sample (0.1-0.3 g.) is dissolved in 20 ml. of an acetic acid-chloroform solution (3 2 by volume), and 2 ml. of saturated aqueous potassium iodide solution is added. The flask is immediately flushed with nitrogen, stoppered, and allowed to stand at room temperature for 15 minutes. Fifty milliliters of water is then added with good mixing, and the liberated iodine is titrated with 0.1 A sodium thiosulfate, employing starch as indicator. A blank titration, which usually does not exceed 0.2 ml., is also run. One milliliter of 0.1 N sodium thiosulfate is equivalent to 0.00821 g. of tetralin hydroperoxide. 

The solvents 1, ethyl acetate-2-propanol-water (126 70 35) 2, 2-propanol-water (90 10) 3, benzene-methanol (10 3) 4, chloroform-acetone (1 7) 5, 1-butanol-acetic acid-ether-water (0 6 3 1) 6, chloroform-2,2,4-trimethylpentane-methanol (50 15 5) 7, chloroform-methanol (10 2). 

The red filtrate in the preceding preparation is treated with hydrochloric acid, the red precipitate dissolved in a little alcohol, some selenium being deposited, and the solution rendered turbid by the addition of water. Shining red needles separate, which after crystallisation melt at 139 5° to 140 5° C. The yield is small. The product is readily soluble in hot alcohol, acetic acid, chloroform or benzene, but insoluble in water. The preparation may be represented as follows ... 

Selenodiglycollic p-toluidide may be prepared from diseleno-diglycollic p-toluidide, or by treating chloraceto-p-toluidide with potassium selenide. The product melts at 217° to 218° C., is soluble in alcohol or hot acetic acid, sparingly soluble in chloroform or benzene, insoluble in water. Selenoxal-p-toluidide separates from dilute alcohol in long, red needles, M.pt. 165° to 166° C., soluble in alcohol, acetic acid, chloroform or benzene, insoluble in water. 

The polymers had molecular weights of several million, but were completely soluble in water and some organic solvents such as chloroform, acetonitrile, ethylene dichloride and acetic acid. The water solubility results apparently from strong hydrogen bonding between solvent and ether groups but appears to be peculiar to the polyethylene oxides for it is not observed with polyformaldehyde, polyacetaldehyde or poly-... 

There have been two additional experiments which verified this basic picture of the nuclear hyperfine interaction in hemins. Johnson (78) increased the spin-lattice relaxation time by performing the Mossbauer experiment under field and temperature conditions which provide a large value of H/T. At 1.6 °K and in an applied field of 30 kG, a magnetic hyperfine interaction corresponding to that expected for high spin Fe(III) and for the g-values is measured experimentally. Recently, Lang et al. have found that a portion of hemin chloride dissolved in tetrahydro-furan at 1 mM concentration displays a hyperfine interaction at 4 °K in zero applied magnetic field. Their conclusion is that a portion of the hemin is present in a monomeric form in this solvent, a situation which is not apparent to any extent in water, acetic acid, chloroform, or dimethyl sulfoxide (77) at any concentrations used. 

As stated above, the utility of silica based stationary phases does not limit its use to organic mobile phases. For many years it has been commonplace in flash chromatography to use aqueous solvents to elute analytes from silica based media. Isocratic elution with mixtures of butanol, acetic acid and water is standard protocol for the separation of amino acids and a carefully prepared combination of methanol, chloroform and water is useful for general organic compounds. Peptides are also readily purified by gradient elution on normal phase silica, moving from acetonitrile to aqueous mobile phase 3,2l This technique is particularly useful for extremely hydrophilic peptides that are not strongly retained on reversed phase media. 

Peroxide Value Accurately weigh about 10 g of sample, add 30 mL of a 3 2 mixture of glacial acetic acid chloroform, and mix. Add 1 mL of a saturated solution of potassium iodide, and mix for 1 min. Add 100 mL of water, begin titrating with 0.05 N sodium thiosulfate, adding starch TS as the endpoint is approached, and continue the titration until the blue starch color has just disappeared. Perform a blank determination (see General Provisions), and make any necessary correction. Calculate the peroxide value, as milliequiva-lents of peroxide per kilogram of sample, by the formula... 

Saturated Potassium Iodide Solution Dissolve excess potassium iodide in freshly boiled water. Excess solid must remain. Store this solution in the dark. Test it daily by adding 0.5 mL to 30 mL of the Acetic Acid-Chloroform Solution, then add 2 drops of starch TS. If the solution turns blue, requiring more than 1 drop of 0.1 N sodium thiosulfate to discharge the color, prepare a fresh solution. 

Procedure Accurately weigh about 5 g of the sample into a 250-mL Erlenmeyer flask. Add 30 mL of the Acetic Acid-Chloroform Solution, and swirl to dissolve. Add 0.5 mL of the Saturated Potassium Iodide Solution, allow the mixture to stand, shaking it occasionally, for 1 min, and add 30 mL of water. Slowly titrate with 0.01 N sodium thiosulfate, shaking the flask vigorously until the yellow color is almost gone. Add about 0.5 mL of starch TS, and continue the titration, shaking the flask vigorously to release all the iodine from the chloroform layer until the blue color disappears. Perform a blank determination, and make any necessary correction. 

Fig. 16.20 represents schematically the phase diagram of the ternary system acetic acid-f water-h chloroform. The pairs water + acetic acid and acetic acid -f chloroform, are completely miscible in all proportions, but water and chloroform are only partially miscible. The composition... 

One key aspect of the sequence of Scheme 3.2 was the use of CeCla to effect selective carbonyl reductions, as pioneered by Luche and co-workers. The CeCls serves two purposes in the reduction of 1 to 8, most importantly, that of allowing selective reduction of the ketone group over the aldehyde. It also exerts a buffering action so that the ester group in 8 and in the alcohol precursor of 11 is not hydrolyzed by water in the solvent. Furthermore, it probably also serves to suppress 1,4-reduction in these conjugated systems. Another point of some interest was the surprising stability of die hemiacetal 8. Evaporation with benzene, benzene-acetic acid, chloroform, acetone, or water only slowly removed the methanol. But, fortunately, two or three evaporations with water—acetic acid—... 

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