Viscous reaction mixtures

Granules can be precipitated and formed by extmding the viscous reaction mixture through a circular die containing several holes over which a knife blade rotates to cut the strands into granules (91). The granules are simultaneously slurried in dilute acetic acid to harden the particles for further washing. 

B. Cyclization. The above oil is poured dropwise into a well-stirred mixture of 110 ml. of 90% phosphoric acid (sp. gr. 1.75) and 23.4 ml. of sulfuric acid (sp. gr. 1.83) which is kept at —10°. The temperature is allowed to rise to 0-10°, and the stirring is continued for 2 hours. The viscous reaction mixture is poured into 500 ml. of ice and w ater, and the acid is partially neutralized with 300 ml. of 40% sodium hydroxide solution with efficient cooling. The viscous cream-colored oil is extracted with three 150-ml. portions of ether the ether extract is washed well with water and sodium bicarbonate solution to remove the last traces of acid and then dried over anhydrous sodium sulfate. The... 

Multiphase or viscous reaction mixtures cannot be stirred well. 

The viscous reaction mixture is then poured into 1.5 liters of ice water and agitated to form a uniform solution. The solution is treated with activated carbon and filtered. Thereafter, 80% acetic acid is added until the filtered solution remains acidic to litmus. The precipitate formed is filtered and washed thoroughly with distilled water. The product is air-dried at a temperature of 95° to 100°C for 48 hours to yield 133 grams of 5-allyl-5-(1-methylbutyl)-2-thiobarbituric acid having a melting point of 132° to 133°C and assaying at 99.5% pure, from U.S. Patent 2,876,225. 

The checkers found the reaction mixture to be dark but not viscous. In experiments in which a magnetically stirred autoclave was used, dark viscous reaction mixtures were obtained, but no product. 

Clarke, H. T. etal., Org. Synth., 1941, Coll. Vol. 1, 543-544 During oxidation of TNT in sulfuric acid to trinitrobenzoic acid, stirring of the viscous reaction mixture must be very effective to prevent added portions of solid dichromate causing local ignition. 

Owing to the viscous reaction mixture, it is necessary to use a mechanical stirrer (magnetic stirring is insufficient). 

Mechanical stirring is recommended for testing polymerization reactions or viscous reaction mixtures. This requires the use of taller containment vessels than the original to install the electric motor for the agitator. 

Switchable polarity solvents have recently been used in two chemical syntheses the polymerization of styrene (Figure 9.7) and carbon dioxide-epoxide copolymerization (Figure 9.8). In the first study,a non-stoichiometric mixture of DBU and 1-propanol was used as this gave a less viscous reaction mixture, which facilitated the filtration step and the isolation of the polystyrene. The recovered ionic liquid was turned back into the less polar mixture using nitrogen and could be reused four times with the addition of some makeup solvent to replace that lost in the filtration step. 

Forty-three grams (1.0 mole) of ethyleneimine (p. 153) (Caution— volatile and toxic substance) is placed in a flask equipped with a reflux condenser. The reaction mixture is held at 60° by external cooling while a stream of hydrogen sulfide is introduced. After there is no evolution of heat upon introduction of hydrogen sulfide (about 50 minutes), the liquid, viscous reaction mixture is dissolved in 1.25 times its volume of absolute ethanol and cooled overnight in the refrigerator. The precipitated /S-aminoethyl mercaptan (5.6 g.) is filtered off, and the ethanol is evaporated from the filtrate under reduced pressure. The residual liquid is distilled under reduced pressure, and 4.9 g. additional /ff-aminoethyl mercaptan sublimes during the first part of the distillation. Bis-2-aminoethyl sulfide is collected at 130-131 °/22 m. There is obtained 29.8 g., or a 50% yield. 

A distinction is usually made between close clearance/large diameter and small diameter/high speed impellers. The first class is used for viscous reaction mixtures. It includes anchor stirrers and helical ribbons. The diameter of these agitators typically is between 70 and 100 % of the tank diameter. 

A) Preparation of Thenylidene-(2)-Phthalide 24.2 g of thienyl-(2)-acetic acid, 52.0 g of phthalic acid anhydride, 4.0 g of anhydrous sodium acetate and 125 ml of 1-methylpyr-rolidone-(2) are heated while stirring in an open flask for 3 hours to 205° to 208°C, while nitrogen is passed through. It is then cooled and the viscous reaction mixture poured into... 

Polymeric substrates or metabolites and mycelial growth often produce very viscous reaction mixtures which are generally pseudoplastic non-Newtonian again these conditions tend to limit desirably high flow dynamics in bioreactors. 

A mixture of 20 mL polyphosphoric acid and 2.0 g 2-formamidobiphenyl in a 100-mL round-bottomed flask was heated at 140-160° C for 1 h with constant stirring. The viscous reaction mixture was then poured into 200 mL cold water. The resulting milky solution was basified to pH 10 with a strong NaOH solution and allowed to stand several hours at room temperature. The light pink solid was filtered, washed extensively with water, and dried to give 1.70 g phenanthridine, in a yield of 93.4%, m.p. 104.5-106°C. The product can be further purified by recrystallization from ligroin to colorless needles, m.p. 106-107°C. 

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