Filtration washing

Difluorodiphenyl. Bis-diazotise a solution of 46 g. of benzidine (Section IV,88) in 150 ml. of concentrated hydrochloric acid and 150 ml. of water by means of a solution of 35 g. of sodium nitrite in 60 ml. of water add about 200 g. of crushed ice during the process (compare p-Fbtorotoluene above). Filter the solution and add it to a filtered solution of 85 g. of sodium borofluoride in 150 ml. of water. Stir for several minutes, collect the precipitated bis-diazonium borofluoride by suction filtration, wash with 5 ml. of ice-cold water, and dry at 90-100°. Place the dry salt in a flask fitted with an air condenser, immerse the flask in an oil bath, and slowly raise the temperature to 150° (Fume Cupboard ). When decomposition of the salt is complete, steam distil the mixture collect the 4 4 difluoro-diphenyl which passes over and recrystallise it from ethanol. The yield is 21 g., m.p. 92-93°. 

Reflux a mixture of 22 5 g. of crude p-nitrobenzal diacetate, 50 ml. of alcohol, 50 ml. of water and 5 ml. of concentrated sulphuric acid for 30 minutes, filter through a fluted paper, and cool the filtrate in ice. Collect the crystals hy suction filtration, wash with cold water, and dry in a vacuum desiccator. The yield of p nitrohenzaldehyde, m.p. 106° is 12 g. (3). 

A simplified procedure is possible by using polyphosphoric acid as the condensing agent. Add 160 g. of polyphosphoric acid to a solution of 11 g. of resorcinol in 13 g. of ethyl acetoacetate. Stir the mixture and heat at 75-80° for 20 minutes, and then pour into ice-water. Collect the pale yellow solid by suction filtration, wash with a little cold water, and dry at 60°. The yield of crude 4-methyl-7-hydroxycoumarin, m.p. 178-181°, is 17 g. Recrystalbsation from dilute ethanol yields the pure, colourless compound, m.p. 185°. 

Reflux 14 6 g. of the ester with a solution of 10 g. of sodium hydroxide in 125 ml. of 80 per cent, methanol for 2 hours on a water bath. Add 200 ml. of water to dissolve the solid which separates, extract with two 30 ml. portions of ether, and warm the aqueous solution on a water bath to remove dissolved ether. Acidify the ice cold aqueous solution to litmus by the addition of concentrated hydrochloric acid. Collect the precipitated acid by suction filtration, wash it with a little cold water, and dry at 100°. The yield of sebacic acid, m.p. 133°, is 11 - 5 g... 

Reflux a mixture of 7 3 g. of methyl myristate with a solution of 4 8 g. of sodium hydroxide in 200 ml. of 90 per cent, methanol for 2 hours, distil off the methanol on a water bath, dissolve the residue in 400 ml. of hot water, add 15 ml. of concentrated hydrochloric acid to the solution at 50° in order to precipitate the organic acid, and cool. Collect the acid by suction filtration, wash it with a little water and dry in a vacuum desiccator. The yield of myristic acid (tetradecanoic acid tetradecoic acid), m.p. 57-58°, is 5 9 g. 

Introduce a solution of 100 g. of sodium bisulphite in 200 ml. of water and continue the stirring, preferably for 10 hours with exclusion of air. A thick precipitate separates after a few minutes. Collect the bisulphite compound by suction filtration, wash it with ether until colourless, and then decompose it in a flask with a lukewarm solution of 125 g. of sodium carbonate in 150 ml. of water. Separate the ketone layer, extract the aqueous layer with four 30 ml. portions of ether, dry the combined organic layers over anhydrous magnesium sulphate, remove the ether at atmospheric pressure, and distil the residual oil under reduced pressure from a Qaisen flask with fractionating side arm (Fig. II, 24, 5). Collect the cyclo-heptanone at 64r-65°/12 mm. the yield is 23 g. 

Nitrosomethylurea. Acetamide method. To a solution of 59 g. of acetamide in 88 g. (28 ml.) of bromine (1) in a 4-litre beaker add dropwise, with hand stining, a solution of 40 g. of sodium hydroxide in 160 ml. of water. Heat the resulting yellow reaction mixture on a steam bath until eflfervescence sets in (2), after which continue the heating for 2-3 minutes. CrystaUisation of the product from the yellow or red coloured solution usually commences immediately. Cool in an ice bath for 1-2 hours, collect the product by suction filtration, wash with a little ice-cold water, and dry in the air. The yield of colourless acetylmethylurea, m.p. 178-180°, is 50 g. 

Phthalylacetic acid. Heat a mixture of 30 g. of phthalic anhydride, 40 ml. of acetic anhydride and 5 g. of potassium acetate under reflux in an oil bath at 155-165° for 15 minutes. Pour the reaction mixture into ice-cold water, collect the yellow precipitate by suction filtration, wash it three times with 25 ml. of water and once with 10 ml. of 50 per cent, ethanol. Dry the. product at 100° the yield of crude plithalylaeetie acid is 20 g. Recrystallise from hot methanol yellow needles, m.p. 245-246°, are obtained. 

Neutrahse about one third of the filtrate with 5N sodium hydroxide and add a further 2 ml. of the alkah solution. Add 1 ml. of benzoyl chloride and stir until the odour of the acid chloride disappears. Collect the solid by suction filtration, wash it with water until free from alkah, and then recrystalhse it from dilute alcohol. The product is the dibenzoyl derivative of hexamethylenediamine and melts at 159°. 

The soiution is aliowed to cool and the crystals of the P2P-bisulfite addition compound are then separated by vacuum filtration, washed with a little clean dH20 then washed with a couple hundred mLs of ether, DCM or benzene. The filter cake of MD-P2P-bisulfate is processed by scraping the crystals into a flask and then 300mL of either 20% sodium carbonate solution or 10% HCi soiution are added (HCI works best). The soiution is stirred for another 30 minutes during which time the MD-P2P-bisulfite complex will be busted up and the P2P will return to its happy oil form. The P2P is then taken up with ether, dried and removed of the solvent to give pure MD-P2P. Whaddya think of that ... 

The pyruvic acid (28.8 g, 0.10mol) was dissolved in 1 NNaOH (300 ml) and stirred at 0 "C. A solution of 30% HjOj (11.3 ml, 0.10 mol) was added dropwise. The solution was stirred for 1 h at 5 C and then acidified with dil. HCl. The precipitate was collected by filtration, washed with water, dried and recrystallizcd from hcxanc-EtOAc to yield 22.2 g (8,5% yield) of the product. 

A solution of sodium methoxide (25% w, 115 ml, 532 mmol) in methanol (187 ml) was cooled to — 8 "C under nitrogen. A solution of 2,4,5-trimethoxy-benzaldehyde (25 g, 128 mmol) and methyl azidoacetate (59 g, 513 mmol) in a 1 2 mixture of methanol-THF (50 ml 4- 100ml) was added dropwisc to the sodium methoxide solution with stirring at — 8°C over a period of 45 min. The solution was stirred and kept below 5°C for 2 h. The mixture was then poured onto ice (1 kg) and stirred. The precipitate which resulted was collected by filtration, washed with water and dried over CaCl in a vacuum desiccator. The dried precipitate was dissolved in EtOAc (600 ml) and dried over Na2S04. 

POCI3 (5 ml, 0.05 mol) was added dropwise to DMF (16 g, 0.22 mmol) at a temperature of 10-20°C. Indole (5.85 g, 0.50 mmol) in DMF (4 ml) was then added slowly with stirring at a temperature of 20-30°C. The mixture was kept at 35°C for 45 min and then poured on to crushed ice and the clear solution treated at 20-30 C with aq. NaOH (20%, 0.24 mol) at such a rate that the solution was always acidic. The last quarter was added all at once and the solution quickly boiled for 1 min. The product was collected by filtration, washed with water and dried to yield 6.93 g (95% yield) of product. 

Horizontal filter surfaces also allow a high degree of control over cake formation. Allowances can be made for changed feeds and/or different cake quality requirements. This is particularly tme of the horizontal belt vacuum filters. With these units the relative proportions of the belt allocated to filtration, washing, drying, etc, as well as the belt speed and vacuum quality, can be easily altered to suit process changes. 

The magnesia and alumina suspension is prepared by treatment of an aqueous solution, containing aluminum and magnesium salt in the desired proportion, with sodium hydroxide. The coprecipitated aluminum and magnesium hydroxides are collected by filtration, washed free of soluble salts, and stabilized by the addition of a suitable hexatol. 

Magaldrate is prepared by precipitation from aqueous solutions of sodium or potassium aluminate and a magnesium salt under controlled conditions of concentration and temperature. The precipitated product is collected by filtration, washed to remove soluble by-products, and dried. 

Dimenhydrinate. Dimenhydrinate [523-87-5] (Dramamine) (18) is a white crystalline, odorless powder that melts between 102 and 107°C. It is sparingly soluble in water, freely soluble in ethanol and chloroform, and sparingly soluble in diethyl ether. Dimenhydrinate is prepared by combining dimethylaminoethyl ben2hydryl ester with 8-ch1orotheophy11ine and refluxing in an isopropyl alcohol solution. The crystalline precipitate of dimenhydrinate that forms on cooling is collected by filtration, washed with cold ethyl acetate, and dried. 

A typical process for the preparation of a poly(methyl methacrylate) suspension polymer involves charging a mixture of 24.64 parts of methyl methacrylate and 0.25 parts of benzoyl peroxide to a rapidly stirred, 30°C solution of 0.42 parts of disodium phosphate, 0.02 parts of monosodium phosphate, and 0.74 parts of Cyanomer A-370 (polyacrylamide resin) in 73.93 parts of distilled water. The reaction mixture is heated under nitrogen to 75°C and is maintained at this temperature for three hours. After being cooled to room temperature, the polymer beads are isolated by filtration, washed, and dried (69). 

The effluent from the reactor is a slurry of terephthaUc acid because it dissolves to a limited extent in almost all solvents, including the acetic acid—water solvent used here. This slurry passes through a surge vessel that operates at a lower pressure than the reactor. More terephthaUc acid crystallizes and the slurry is then ready to be processed at close to atmospheric conditions. The terephthaUc acid crystals are recovered by filtration, washed, dried, and conveyed to storage, from which they are in turn fed to the purification step. 

Diacetone-L-sorbose (DAS) is oxidized at elevated temperatures in dilute sodium hydroxide in the presence of a catalyst (nickel chloride for bleach or palladium on carbon for air) or by electrolytic methods. After completion of the reaction, the mixture is worked up by acidification to 2,3 4,6-bis-0-isoptopyhdene-2-oxo-L-gulonic acid (2,3 4,6-diacetone-2-keto-L-gulonic acid) (DAG), which is isolated through filtration, washing, and drying. With sodium hypochlorite/nickel chloride, the reported DAG yields ate >90% (65). The oxidation with air has been reported, and a practical process was developed with palladium—carbon or platinum—carbon as catalyst (66,67). The electrolytic oxidation with nickel salts as the catalyst has also... 

Meldrum s acid (3) To malonic acid 1 (52 g, 0 5 mol) in acetic anhydride (60 mL, 0 6 mol) was added cone HjSOa while stimng Acetone 2 (40 mL, 0 55 moO was added Cooling lor 24 h, filtration, washing the solid with ice water and recrystallization from acetone-water gave 3 (35 g, 49%), mp 94-95 C (dec)... 

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