Still-head temperature

Product is collected until the still head temperature reaches 110 °C. At this point the heating mantle is removed, the nitrogen flow is increased slightly, and the distillation flask is allowed to cool. When the latter is cool enough to touch, the receiving flask is carefully disconnected under a positive N2 flow, and capped. The warm residue in the distillation flask (which solidifies on... 

Ethylenedioxy-17oc,21 -dihydroxypregn-S-ene-11,20-dione 21-Acetate.6 A stirred mixture of cortisone acetate (9.5 g), ethylene glycol (200 ml) and p-tol uenesulfonic acid monohydrate (0.3 g) is distilled over a period of 4 hrs at about 1-2 mm (temperature of reaction mixture 72-81°, still-head temperature 60-80°). The reaction mixture is made alkaline with alcoholic potassium hydroxide and poured into water. The solid is collected, dried [9.25 g (88% crude yield)], mp 260-265°, and crystallized from pyridine-water to give 8.2 g (78%), mp 268-271°. 

Preparation from Ethyl Allophanate. Thirteen and two-tenths grams of ethyl allophanate (0.1 mol), 15 ml. of 100% hydrazine hydrate (0.3 mol), and 100 ml. of water are placed in a 200-ml. three-necked flask equipped as in procedure A. The reaction mixture is heated for 3%. hours, during which the pot temperature rises from 25 to 101° and the still-head temperature rises from 25 to 99°. Fifteen milliliters of distillate is collected. 

The flask must be heated slowly at the initial stage to drive off any volatile impurities, and subsequently to go ahead with the process of distillation. The still-head temperature must be controlled and monitored carefully and a forerun and a main desired fraction should be collected that must get distilled at a fairly constant temperature. 

In a 500 ml. three-necked flask, equipped with a thermometer, mechanical stirrer and efficient reflux condenser, dissolve 16 g. of sodium hydroxide pellets in 95 ml. of hot methyl alcohol. Add 49 g. of guanidine nitrate, stir the mixture at 50-65° for 15 minutes, and then cool to about 20°. Filter oflF the separated sodium nitrate and wash with two 12 ml. portions of methyl alcohol. Return the combined filtrates to the clean reaction flask, add 69 g. of sulphanilamide (Section IX,9) and stir at 50-55° for 15 minutes. Detach the reflux condenser and, with the aid of a still-head ( knee-tube ), arrange the apparatus for distillation from an oil bath with stirring about 100 ml. of methyl alcohol are recovered. Add 12 g. of pure cycZohexanol. Raise the temperature of the oil bath to 180-190° and continue the distillation. Reaction commences with the evolution of ammonia when the uiternal temperature reaches 145°. Maintain the... 

A 500-ml, three-necked, round-bottom flask is equipped with a condenser, a dropping funnel, and a thermometer in the reaction mixture. In the flask is placed a mixture of 85% hydrazine (115 ml, 118 g) and 225 ml of 95% ethanol with a few boiling chips. The solution is brought to reflux (mantle) and cinnamaldehyde (100 g, 0.76 mole) is added dropwise over about 30 minutes followed by an additional 30 minutes of refluxing. A still head is attached to the flask and volatiles (ethanol, water, hydrazine hydrate) are slowly distilled at atmospheric pressure until the pot temperature reaches 200° (about 3 hours). Hereafter, phenylcyclopropane is collected over the range 170-180°. When the pot temperature exceeds 250°, the recovery is complete. The crude product (55-65 g) is washed twice with 50-ml portions of water and dried (anhydrous potassium carbonate). Distillation under vacuum through a short column affords the product, bp 60°/13 mm, 79-80°/37 mm, n f 1.5309, about 40 g (45%). 

Dithioglycerol is isolated from the oil by distillation from an oil heated pot through a short still. The distillation is carried out at a pressure of less than 1 mm and at a bath temperature of 120°-175°C, the dithioglycerol distilling over at a head temperature of 60°-65°C/0.2 mm or 75°-80°C/0.8 mm. Starting from 550 parts of crude dithioglycerol, 340 parts of distillate is obtained which contains 53% of mercapto sulfur and is nearly pure... 

A 2-1. three-necked flask is mounted on a steam bath and fitted with a reflux condenser, a separatory funnel, and an efficient sealed stirrer. In the flask is placed 600 cc. of absolute alcohol, and to this is added gradually 46 g. (2 gram atoms) of clean sodium cut into small pieces.1 The sodium ethoxide solution is stirred and cooled to room temperature, after which 267 g. (260 cc., 2.05 moles) of ethyl acetoacetate (Note 1) is added slowly through the separatory funnel. The reflux condenser is then replaced by a short still head, and the alcohol is removed by distillation at approximately room temperature and under the pressure of a water pump. When approximately half the alcohol has been removed, sufficient sodium enolate precipitates so that stirring has to be discontinued. When the residue appears dry (after about two hours) the last traces of alcohol are removed by heating for an hour on the steam bath under a pressure of 2 mm. The flask is allowed to cool to room temperature under reduced pressure. 

C. 3-Chloro-2-(chloromethyl)-1-propene. Tris(chloromethyl)acetic acid (205 g, 1.00 mol) is transferred to a 500-mL, two-necked, round-bottomed flask. On top of the powdery acid, which nearly fills the flask, is placed a football magnetic stir bar (1.25 x 0.5 in.). The neck of the flask to be clamped is wrapped well with aluminum foil and is fitted with a glass stopper. A standard taper 24/40 short path still head, to which is attached a Drierite drying tube, is attached at the second neck. The upper flask and short path column are wrapped with aluminum foil, and the flask is immersed in a high temperature oil bath (Note 14) that has been preheated to a stable 210°C. As the solid melts, the reaction mixture becomes yellow, and the oil bath temperature drops (IQ-... 

A. N,N-Diethyl-2,2,2-trichloroacetamide. A 1-1. three-necked flask equipped with a stirrer and dropping funnel is charged with 73 g. (1.00 mole) of diethylamine, 500 ml. of ether, and a solution of 40 g. (1.00 mole) of sodium hydroxide in 160 ml. of water. The mixture is stirred and maintained at a temperature of —10° to — 15° by a bath of Dry Ice and acetone while 200 g. (1.10 moles) of trichloroacetyl chloride is added in the course of 1 hour. The cooling bath is removed, the temperature is allowed to rise to 10°, and the organic layer is separated. The aqueous layer is extracted with two 50-ml. portions of ether. The ether extracts are combined, washed with 50 ml. of 5% hydrochloric acid, two 50-ml. portions of 5% sodium bicarbonate solution, and 50 ml. of water, and dried over magnesium sulfate. The ether is removed by distillation at atmospheric pressure. The residue is distilled through a short indented Claisen still head at reduced pressure. N,N-Diethyl-2,2,2-trichloroacetamide is collected at 77-79°/1.5 mm. 1.4902-1.4912 weight 183-200 g. (84-92%). 

C. 2,3-Dicyano-l,4,4a,9a-fefrahydro/luorefie (3). A 100-ml., round-bottomed flask, equipped with a reflux condenser under nitrogen pressure, is charged with 10.4 g. (0.10 mole) of crude cyclobutene 2, 23.3 g. (0.20 mole) of indene (Note 7), and 0.3 g. of hydroquinone. The reaction mixture is stirred and heated at 150° for 4 hours under nitrogen. The reflux condenser is then replaced by a still head, and 6.3 g. (0.053 mole) of indene is distilled from the flask at a bath temperature of about 95° and a pressure of 11 mm. (Note 8). The dark-colored reaction mixture is transferred to a 500-ml., round-bottomed flask, diluted with 200 ml. of benzene followed by 1 g. of decolorizing carbon, and the resulting mixture is refluxed for 2 hours. After the mixture is cooled to room temperature, the carbon is removed by filtration, and the benzene is distilled. The residual oily residue solidifies on standing and is recrystallized from 45 ml. of ethanol to yield 15.4-15.9 g. (70-72%) of crystalline fluorene 3, m.p. 98.5-100° (Note 9). 

It forms a picrate m 149° (from EtOH-pet ether) from which the free base can be recovered using a basic ion exchange resin and can then be distd through a Todd column using an automatic still head which only collects products boiling below 51°/atm. Polymeric materials if present will boil above this temperature. The hydrochloride has m 85-86°. The pKa in 40% EtOH is 5.33. [Roberts and Chambers JACS 73 5030 1951, Jones JOC 9 484 7944 Emmons J A CS 79 6522 1957. ... 

Into a 300-ml. three-necked flask equipped with a nitrogen inlet, a thermometer, and a short fractionating column (Note 1) are charged 74.1 g. (0.50 mole) of triethyl orthoformate, 51.0 g. (0.50 mole) of phenylacetylene (Note 2), and 3.0 g. of zinc iodide (Note 3). Ethanol is slowly distilled from the reaction mixture, which must be heated to about 135° before refluxing in the still-head begins. A total of 29-35 ml. of distillate, b.p. 65-88° (mostly 78°), is collected over a period of about 1 hour as the temperature of the reaction mixture gradually rises to 200° to 210° (Note 4). The reaction mixture is cooled to room temperature and filtered with suction. The flask and the small amount of precipitate on the filter paper are washed with 5 ml. of ether. The filtrate and ether wnshings are combined and distilled. After... 

Connections should be of glass since cork and rubber are attacked readily. Since nitrosobenzene decomposes at the elevated temperature, it should be steam-distilled as rapidly as possible. If several runs are made, not more than four or five should be combined for distillation. A Hopkins still head is effective for preventing contamination. 

The stirrer is then replaced by a short still head connected to a long (90-cm.) air condenser and receiver (Note 8), and the product is distilled at atmospheric pressure as long as any distillate is obtained. The temperature of the vapor rises gradually to 340°. The distillate, which consists chiefly of water, dinitrile,... 

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