Dry ice-solvent baths

When condensing explosive gases, the temperature of the bath and the effect on the reactant gas of the condensing material selected must be determined experimentally (see Chapter 6, section 6.D). Very small quantities should be used because detonations may occur. A taped and shielded Dewar flask should always be used when condensing reactants. Maximum quantity limits should be observed. A dry ice solvent bath is not recommended for reactive gases liquid nitrogen is recommended. (See also Chapter 3, section 3.D.3.I.)... 

A 100-ml flask is charged with 25 ml of bromine and 10 g of adamantane and heated under reflux for 3 hours. The cooled mixture is dissolved in 100 ml of carbon tetrachloride, and the carbon tetrachloride solution is washed with 100-ml portions of saturated bisulfite solution until the color of bromine is discharged. The solution is then washed twice with water and dried (magnesium sulfate). The solvent is removed (rotary evaporator) and the product is recrystallized from methanol. (For best recovery of the recrystallized material, the methanol solution should be cooled in a Dry Ice cooling bath.) The product has mp 108°. 

Acetylcyclohexanone. Method A. Place a mixture of 24-6 g. of cyclohexanone (regenerated from the bisulphite compound) and 61 g. (47 5 ml.) of A.R. acetic anhydride in a 500 ml. three-necked flask, fitted with an efficient sealed stirrer, a gas inlet tube reaching to within 1-2 cm. of the surface of the liquid combined with a thermometer immersed in the liquid (compare Fig. II, 7, 12, 6), and (in the third neck) a gas outlet tube leading to an alkali or water trap (Fig. II, 8, 1). Immerse the flask in a bath of Dry Ice - acetone, stir the mixture vigorously and pass commercial boron trifluoride (via an empty wash bottle and then through 95 per cent, sulphuric acid) as fast as possible (10-20 minutes) until the mixture, kept at 0-10°, is saturated (copious evolution of white fumes when the outlet tube is disconnected from the trap). Replace the Dry Ice-acetone bath by an ice bath and pass the gas in at a slower rate to ensure maximum absorption. Stir for 3 6 hours whilst allowing the ice bath to attain room temperature slowly. Pour the reaction mixture into a solution of 136 g. of hydrated sodium acetate in 250 ml. of water, reflux for 60 minutes (or until the boron fluoride complexes are hydrolysed), cool in ice and extract with three 50 ml. portions of petroleum ether, b.p. 40-60° (1), wash the combined extracts free of acid with sodium bicarbonate solution, dry over anhydrous calcium sulphate, remove the solvent by... 

Liposphere formulations are prepared by solvent or melt processes. In the melt method, the active agent is dissolved or dispersed in the melted solid carrier (i.e., tristearin or polycaprolactone) and a hot buffer solution is added at once, along with the phospholipid powder. The hot mixture is homogenized for about 2 to 5 min, using a homogenizer or ultrasound probe, after which a uniform emulsion is obtained. The milky formulation is then rapidly cooled down to about 20°C by immersing the formulation flask in a dry ice-acetone bath, while homogenization is continued to yield a uniform dispersion of lipospheres. 

The bomb tubes are returned to the dry ice-acetone bath. After cooling thusly, the tubes are drawn out to a fine capillary to allow the ammonia to escape, and the entire reaction mixture is immediately collected in an excess of dilute HCl acid solution. Evaporate the acidic solution to dryness on a steam bath, desiccate the residue, and extract in a soxhlet extractor for 12 hours using chloroform as the solvent (dry chloroform) and taking care to exclude all H2O. Distill off the chloroform and if separation is not important to you, then you can use the combination of all three amines in a synthesis calling for any one of the three. 

A solution of 52.2 g (0.31 mol) of ( )-(lS.2S)-2-amino-l-phenyl-l,3-propanediol and 0.37 mol of Ihe orthoester (previously distilled), in 90 mL of DMF is heated to 110 5C for 9.5 h and the solvent removed in vacuo. The resulting oil. which crystallizes on standing, is treated with 30 mL of diethyl ether, cooled in a dry ice- acetone bath, and the crystalline material is collected. This material is dissolved in 300 mL of diethyl ether, treated with charcoal, filtered, concentrated to 125 mL, and cooled to — 78 C. The crystalline product is washed with 10 mL of diethyl ether, previously cooled to — 78 C. 

The lilac colored reaction mixture is transferred into a second Schlenk flask (100 mL) using a double-ended stainless steel cannula. The second flask contains hexane previously cooled to — 78 °C (Dry Ice-acetone bath). A lilac colored solid precipitates. The solvent is siphoned off and the solid is washed three times with hexane (20mL) previously cooled to — 78 °C and transferred into the flask using the double ended cannula technique. The wash solvent is siphoned off and remaining solid is dried under vacuum (10-3torr, oil pump) at -40°C for 8h. Yields for MoCp(CO)3(FBF3) 282 319 mg (85-96%), for WCp(CO)3 (FBF3) 357-378 mg (85-90%). 

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