Separation browning products

Under N2, clean Li metal (0.17 g, 25 mmol) was placed in a round-bottom flask with a solvent mixture of MeOH (3 mL) and pcntan-t-ol (17 mL). The mixture was heated under N, until the reaction with Li was complete. Then, naphthalene-2,3-dicarbonitrilc (2 g, 11 mmol) was added to the mixture which turned green-brown the mixture was refluxed for 3h. The brown powder, obtained after cooling and removal of the solvent under reduced pressure, was dissolved in anhyd acetone (20 mL) and then hexane (70 mL) was added. The green precipitate was separated from the brown solution by filtration. This purification by precipitation was repeated twice. The green precipitate was placed in a Soxhlet extractor and extracted for 3 h with acetone (200 mL) in order to separate the product from the insoluble metal-free species and LiOH. The acetone solution was evaporated down to a volume of 20 mL. The product precipitated after the addition of hexane (70 mL). This latter purification step was performed several times yield 1.29 g (64%). 

The product was pumped in a C02 atm into a 10 liter separator, H O was recycled and the product washed with H20 in a 60 liter column with passing of C02 to an acidity of 0.001-0.005% H2S04. The earlier process without C02 yielded a dark-red to brown product of 0.03-0.05% acidity... 

On allowing V(acac)3 to react with di(am)sar (172) for 3 days under N2, a deep red-brown developed.893 After separation (by cation exchange chromatography) of the red-brown product, its crystalline chloride was converted into the dithionate [Vrv(di(amH)sar-... 

Color production is the primary characteristic of the Flaillard reaction, yet surprisingly little is known about any chromophores present (j ). In view of the labile nature of at least some of the browning products, rapid separation of these complex mixtures with minimal exposure to heat and air is necessary. High-performance liquid chromatography promised to provide almost the ideal answer. 

Zinc(III) tetrapentafluorophenylporphyrin was synthesized via condensation of pyrrole, pentafluorobenzaldehyde and zinc acetate in 2,4,6-trimethylpyridine, according to a described technique [44,46], The target product, a brown-colored solid, was obtained by consecutive vacuum distillation, filtration and chromatographic separation. The product was IR analyzed, which indicated the absence of group ... 

To 3(X) g. (1.75 moles) of the brown product above are added 100 g. of finely crushed ice and 400 ml. of ether. A cold solution of 70 g. (1.75 moles) of sodium hydroxide in 150 ml. of water is added with stirring, the temperature of the reaction mixture being held at 5° during this operation. After standing several minutes, the ether layer is separated and dried over Drierite. Removal of the ether under vacuum gives 202 g. (85% yield based on the hydrochloride) of 2-diethylaminoethyl chloride (Caution—toxic material) as a red oil. Further purification may be effected by distillation, the product boiling at 69°/50 mm. The free base is unstable and should be made up as needed from the stable hydrochloride salt. 

To a boiling concentrated solution of barium azide, copper(II) azide is added until saturation. Upon cooling brown crystals of barium tetraazidocuprate(II) dihydrate are separated. The product is washed with ether and dried at 120°C to yield the anhydric compound [193]. 

I] could also be prepared by reaction of [II] with two to three equivalents of allyl magnesium chloride in tetrahydrofuran at room temperature pure [I] could be isolated from the violet reaction mixture in the same way as described above. If only one equivalent of allyl magnesium chloride was used, however, the solution turned brown after evaporation a brown oil separated. This product may contain allyl-bis(cyclopentadienyl)-titanium monochloride, but so far all attempts to isolate this compound have failed, even when the solvent was varied and the temperature of the solution kept as low as -80°,... 

A portion of the chocolate brown product (3.00 g) is treated with concentrated aqueous HCl (5 mL) while agitating for 10-15 min at room temperature. This step results in the formation of a fine, yeUow-brown precipitate. The precipitate is separated by decanting off the liquid, and then the precipitate is washed with concentrated HCl (5mL) and dissolved in boiling concentrated HCl (20 mL). When the solution cools to room temperature, greenish yellow needles form. The needles are collected by filtration through a coarse porosity fritted glass funnel. The... 

In a 1-litre three-necked flask, fitted with a mechanical stirrer, reflux condenser and a thermometer, place 200 g. of iodoform and half of a sodium arsenite solution, prepared from 54-5 g. of A.R. arsenious oxide, 107 g. of A.R. sodium hydroxide and 520 ml. of water. Start the stirrer and heat the flask until the thermometer reads 60-65° maintain the mixture at this temperature during the whole reaction (1). Run in the remainder of the sodium arsenite solution during the course of 15 minutes, and keep the reaction mixture at 60-65° for 1 hour in order to complete the reaction. AUow to cool to about 40-45° (2) and filter with suction from the small amount of solid impurities. Separate the lower layer from the filtrate, dry it with anhydrous calcium chloride, and distil the crude methylene iodide (131 g. this crude product is satisfactory for most purposes) under diminished pressure. Practically all passes over as a light straw-coloured (sometimes brown) liquid at 80°/25 mm. it melts at 6°. Some of the colour may be removed by shaking with silver powder. The small dark residue in the flask solidifies on cooling. 

Tetrahydrofurfuryl chloride. Place 204 g. (194 ml.) of freshly distilled tetrahydrofurfuryl alcohol (b.p. 177°) and 174 g. (178 ml.) of dry pyridine in a 1-litre three-necked flask, fitted with a dropping funnel, mechanical stirrer and thermometer. Cool in an ice bath, stir vigorously and add 250 g. (153 ml.) of freshly distilled thionyl chloride at the rate of 3-5 drops per second. A pasty crystalline mass begins to separate and the temperar ture commences to rise rapidly when one-third to one-half of the thionyl chloride has been added subsequently the mass largely redissolves and a dark brown liquid forms. Remove the ice bath when the addition is complete and stir the mixture for 3-4 hours. Pour the reaction product into a large separatory funnel and extract with seven 250 ml. portions of ether break up any lumps that may form with a glass rod. Remove the ether from the combined extracts by distillation, wash the residue with three 50 ml. portions of water, dry with anhydrous magnesium sulphate and distil under reduced pressure. The yield of tetrahydrofurfuryl chloride, b.p. 47-48°/15 mm., is 180 g. 

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