Funnel , addition Hirsch

S-ml. portions of water, and dried over anhydrous sodium sulfate. The solvent is removed on a steam bath in a stream of nitrogen and finally at reduced pressure. The crystalline residue of 0.207 g. (Note 7) is recrystallized in a 10-ml. conical flask from 1 ml. of acetone. When the flask has cooled to room temperature, 0.5 ml. of methanol is added, and the flask is chilled to +2° for 2 hours. The crystals are collected on a tared Hirsch funnel of 40-mm. diameter, washed on the funnel with two 0.5-ml. portions of ice-cold methanol, and dried for 2 hours at 40°/2 mm. The first crop of cholestanyl methyl ether thus obtained forms large colorless glistening plates, m.p. 85.5-86° (Note 8). An additional... 

Repeat this rinsing with two additional 0.5-mL portions of ice-cold water. Dry the crystals for 5-10 minutes by allowing air to be drawn through them while they remain on the Hirsch funnel. Transfer the product to a watch glass or a clay plate and allow the crystals to dry in air. It may take several hours for the crystals to dry completely, hut you may go on to the next step before they are totally dry. Weigh the crude product and set aside a small sample for a melting point determination and a color comparison after the next step. Calculate the percentage yield of crude acetaminophen (MW = 151.2). Record the appearance of the crystals in your notebook. 

Bromination and isolation Measure 1 mL of freshly prepared 1 M bromine in dichloromethane directly from the dispenser into the vial. Swirl the vial gently during the addition to mix the contents. After the addition of the bromine solution to the vial is complete, loosely screw a cap onto the vial and stir the mixture for 15 min. Isolate the product by vacuum filtration using a Hirsch funnel. Wash the product with several drops of cold dichloromethane until it is white. Transfer the product to a watchglass or a piece of filter or weighing paper and allow it to air-dry. Using a Craig tube, recrystallize the product from xylenes. 

Allow the solution to cool slowly to room temperature over a period of 15 min and then place it in an ice bath for an additional 10 min. Collect the yellow needles by vacuum filtration using a Hirsch funnel (i ) and then air-dry them on a porous clay plate or on filter paper. 

Chlorobenzoic acid. Dilute the alkaline phase, obtained and saved during the original extraction procedure, by adding 2.0 mL of water. The dilute aqueous phase is then acidified by the addition of 0.4 mL of concentrated hydrochloric acid. Collect the voluminous white precipitate of the product that forms on addition of the acid, under reduced pressure by use of a Hirsch funnel. Rinse the filter cake with 2.0 mL of distilled water (- ). 

Purification and Characterization. The (E)-stilbene obtained is, in most cases, sufficiently pure for characterization. However, this should be confirmed by thin-layer chromatography as ouflined earlier (see Purification and Characterization, Experiment [19A]). If only a trace of the Z isomer is detected, recrystallize the product directly, using absolute ethanol. Collect the recrystaUized material by vacuum filtration using a Hirsch funnel. Maintain the vacuum for an additional 10 min to partially dry the crystalline product. Then place it on a clay plate, or on filter paper, and allow it to dry thoroughly. As an alternative, the product may be dried in a vacuum drying oven (or pistol) for 10-15 min at 30 °C (1-2 mm H. ... 

Purification and Characterization. Collect the crude N,N -diacetyl-l,4-phenylenediamine by vacuum filtration using a Hirsch funnel ( ). Rinse the vial with two 0.5-mL portions of water and use the rinse to wash the filter cake. Place a piece of plastic food wrap over the mouth of the funnel and continue the suction for an additional 5-8 min. Place the collected material on a porous clay plate or filter paper to dry further. 

Acidify fhe aqueous layer by fhe dropwise addition (check with pH paper) of 3 M HCl from a Pasteur pipet until a thick, white precipitate of p-methoxybenzoic acid is formed. Cool the mixture in an ice bath for 5 min and collect the solid by vacuum filtration using a Hirsch funnel ( ). Wash the filter cake with three 0.5-mL portions of cold water (calibrated Pasteur pipet). Maintain the vacuum for approximately 5 min and cover the funnel with plastic food wrap (see Prior Reading) to partially dry the product. Transfer the material to a porous clay plate or filter paper to complete the drying process. 

Isolation of Product Add 1.4 mL of cold methanol with stirring (glass rod), and then cool the mixture in an ice bath for 5-10 min. Collect the dark crystals by filtration under reduced pressure using a Hirsch funnel. Rinse the reaction vial and crystals with a few drops of cold methanol. Continue dropwise addition of cold methanol to the crystals on the filter bed until the product appears purple and is no longer brownish in color. Finally allow the crystalline product to air-dry on a porous clay plate (or in an oven at about 80 °C for 1 h) ( ). 

Isolation of Product. Allow the reaction mixture to cool to room temperature and, in the hood, remove the flask. Transfer the reaction solution using a Fhsteur pipet to a 50-mL Erlenmeyer flask containing 12 mL of ice-cold water. Rinse the round-bottom flask with an additional 3 mL of ice-cold water, and transfer the rinse to the same Erlenmeyer flask in Uke manner. Now add, in small portions, 6 M HQ ( 8 mL) until a white precipitate forms and the solution tests weakly acidic to pH paper. Collect the precipitate of frans-cinnamic add by vacuum filtration using a Hirsch funnel. Wash the white crystals with three 2-mL portions of cold water. To partially dry the material, continue the suction for an additional 15 min (remember to cover the Hirsch funnel with filter paper to protect the filter cake from contamination with dust from the laboratory atmosphere during the extended air-drying period). 

Continue the addition (dropwise) until the reddish-brown color of bromine persists. Now add water (4 drops), cap the vial, shake, vent, and then allow it to stand at room temperature for 10 min. Collect the crystalline precipitate by vacuum filtration using a Hirsch funnel and wash the filter cake with 0.5 mL of 5% aqueous sodium bisulfite solution. Recrystallize the solid derivative from ethanol, or from an efhanol-water mixture, using a Craig tube. Dissolve the material in about 0.5 mL of ethanol, add water until it becomes cloudy, cool in an ice bath, and collect the crystals in the usual manner. Dry the purified product on a porous clay plate and determine the melting point. 

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