Steam distillation under reduced pressure

According to U.S. Patent 3,225,030, 1,500 grams of dried ground plant of Vinca rosea were Intimately mixed with 1,000 ml of a 2% tartaric acid solution, and the mixture was extracted with three 9-liter portions of benzene. The benzene extracts were combined and were concentrated in vacuo to about 1,500 ml. The concentrate was mixed with 1 liter of 2% tartaric acid and the mixture was steam-distilled under reduced pressure until all of the benzene had distilled over. The insoluble residue was dissolved in hot methanol, a second 1-liter portion of 2% tartaric acid solution was added, and the mixture was steam-distilled under reduced pressure until all of the methanol had distilled. 

Ethyl diazoacetate may be purified, but with considerable loss, by steam distillation under reduced pressure.2 3 4 5... 

The third distillate generally contains only 1-2 g. of hydrogen chloride. In checking this preparation on a larger scale, it has been found convenient to add the water continuously below the surface of the boiling syrup this modification, which constitutes a steam distillation under reduced pressure, brings about a more rapid removal of the excess hydrochloric acid. 

The cooked aroma of E paclfica (Pacific krill) is fishy and relatively unacceptable. Its GC profile is quite different than that of other samples, because N,N-dimethyl-2-phenylethyl amine was a principal volatile component while only small quantity of pyrazine and thialdine were observed (see Table I). This amine was not produced by cooking, it occurs in vivo (27). Volatiles from both raw and boiled (85°C, 90 min) E. pacifica were prepared by steam distillation under reduced pressure (20 Torr). 

This method has been used to prepare nanoemulsions of such polymers as cellulose esters and epoxy resins, similar to latexes produced by emulsion polymerization. The nanoemulsions are prepared by direct emulsification of solutions of the polymers in organic solvents, followed by removal of the organic solvent by steam distillation under reduced pressure. The nanoemulsions produced in this fashion had stabilities > 1 year. 

Kumazawa, K. Masuda, H. (2003) Identification of odor-active 3-mercapto-3-methylbutyl acetate in volatile fraction of roasted coffee brew isolated by steam distillation under reduced pressure. J. Agric. Food Chem. 51, 3079-3082. 

Bleaching is achieved by adsorption on activated bleaching clays (sorbents of the aluminium silicate type) or in combination with other adsorbents (such as activated carbon, also known as activated charcoal) to remove oil soluble pigments (such as carotenoids and chlorophylls), residual phosphoHpids, and eventually soap residues resulting from the deacidification process. Volatile substances are removed by deodorisation via steam distillation under reduced pressure. The volatile compounds are mainly responsible for the unpleasant smeU and aftertaste of cmde oil, so this process provides organoleptically neutral, indifferent oils. 

Pour the resulting dark reddish-brown liquid into 500 ml. of water to which 17 ml. of saturated sodium bisulphite solution has been added (the latter to remove the excess of bromine). Steam distil the resulting mixture (Fig. II, 41,1) , collect the first portion of the distillate, which contains a little unchanged nitrobenzene, separately. Collect about 4 litres of distillate. Filter the yellow crystalline solid at the pump, and press well to remove the adhering liquid. The resulting crude m-bromonitrobenzene, m.p. 51-52°, weighs 110 g. If required pure, distil under reduced pressure (Fig. II, 19, 1) and collect the fraction of b.p. 117-118°/9 mm. it then melts at 56° and the recovery is about 85 per cent. 

If pure 3-bromo-4-aminotoluene is required, the crude base may be purified either by steam distillation or, more satisfactorily, by distillation under reduced pressure. The oil is dried with 5 g. of sodium hydroxide pellets, and distilled under reduced pressure from a Claisen fiask with a fractionating side arm a little p-tolui-dine may be present in the low boiling point fraction, and the pure substance is collected at 92-94°/3 inin. or at 120-122°/30 mm. The purified amine solidifies on cooling and melts at 17-18°. 

Heat a suspension of 22 g. of the diacetate in a mixture of 120 ml. of concentrated hydrochloric acid, 190 ml. of water and 35 ml. of alcohol under reflux for 45 minutes. Cool the mixture to 0°, filter the solid with suction, and wash with water. Purify the crude aldehyde by rapid steam distillation (Fig. II, 41, 3) collect about 1500 ml. of distillate during 15 minutes, cool, filter, and dry in a vacuum desiccator over calcium chloride. The yield of pure o-nitrobenzaldehyde, m.p. 44—45°, is 10 g. The crude solid may also be purified after drying either by distillation under reduced pressure (the distillate of rather wide b.p., e.g., 120-144°/3-6 mm., is quite pure) or by dissolution in toluene (2-2-5 ml. per gram) and precipitation with light petroleum, b.p. 40°-60° (7 ml. per ml. of solution). 

Method 1. Reflux a mixture of pure nicotinic acid (Section V,22), 84 g. (105 ml.) of absolute ethanol and 90 g. (50 ml.) of concentrated sulphuric acid in a flask for 4 hours on a steam bath. Cool the solution and pour it slowly and with stirring on to 200 g. of crushed ice. Add sufficient ammonia solution to render the resulting solution strongly alkaline generally, some ester separates as an oil but most of it remains dissolved in the alkaline solution. Extract the solution with five 25 ml. portions of ether, dry the combined ethereal extracts with anhydrous magnesium sulphate, remove the ether and distil under reduced pressure. The ethyl nicotinate passes over at 117-118°/ 6 mm. the yield is 34 g. The b.p. under normal pressure is 222-224°. 

After separation of the catalyst by filtration, raw succinic anhydride is purified by distillation under reduced pressure, ie, 4—13 kPa (30—98 mm Hg), and flaked. The material of constmction of the plant is stainless steel. Typical specific consumptions for the production of one metric ton of succinic anhydride are maleic anhydride at 1050 kg hydrogen, 300 m steam, 4500 kg cooling water, 100 m electricity, 350 kW nitrogen, 100 m and methane,... 

The base may be purified by steam distillation but distillation under reduced pressure is more satisfactory. The oil is dried over 5 g. of solid sodium hydroxide and distilled in vacuo. I he first portion of the distillate may contain -toluidine and must be carefully separated, as it causes rapid discoloration. The 3-bromo-4-aminotoluene is obtained as a colorless liquid of b.p. i20-i22°/30 mm. or 92-94 /3 mm. It solidifies on cooling and melts at 16-18°. The loss on purification is about 15 per cent of the weight of the crude base. 

In a i-l. three-necked flask are mixed 150 g. (r.63 moles) of /3-hydroxyethyl methyl sulfide (p. 54) (Note i) and 200 g. of dry chloroform (Note 2). The flask is placed on a steam bath and is fitted with a dropping funnel, a mechanical stirrer, and a condenser. The condenser is fitted with a trap to remove the vapors of hydrogen chloride and sulfur dioxide (page 2). A solution of 204 g. (1.7 moles) (Note 3) of thionyl chloride in 200 g. (135 cc.) of dry chloroform is added dropwise to the /3-hydroxyethyl methyl sulfide over a period of about two hours (Note 4). The reaction mixture is stirred vigorously during this addition and for about four hours after the addition is complete. The chloroform is distilled on the steam bath and the residue is distilled under reduced pressure. The yield is 135-153 g- (75 5 per cent of the theoretical amount) of a product boiling at 55-s6°/3o mm- (Note 5). 

The solution of sodium methyl sulfide in absolute alcohol is transferred to a 3-I. three-necked flask, which is placed on a steam bath and fitted with a dropping funnel, a reflux condenser, and a mechanical stirrer. The solution is heated until the alcohol begins to boil. Heating is then discontinued and 302 g. (3.7s moles) of ethylene chlorohydrin (Note 5) is added dropwise with efficient stirring over a period of about two hours (Note 6). The reaction mixture is concentrated by distilling as much of the alcohol as possible on the steam bath. The mixture is then allowed to cool and the sodium chloride removed by filtration. The flask is rinsed, and the sodium chloride washed with three loo-cc. portions of 95 per cent alcohol. The combined filtrate and washings are concentrated on the steam bath under reduced pressure until no further distillate passes over. The residue is then transferred to a modified Claisen flask (Org. Syn. Coll. Vol. i, 125) and fractionally distilled under reduced pressure. The yield is 238-265 g. (74-82 per cent of the theoretical amount based on the sodium used) of a product boiling at 68-7o°/20 mm. 

Methylfurfural may be prepared by a modification of this method, which is more rapid but gives lower yiddsd A solution of 800 g. of sucrose in i 1. of hot water is allowed to flow slowly into a boiling solution of 500 g. of stannous chloride crystals, 2 kg. of sodium chloride, and 4 1. of 12 per cent sulfuric acid in a 12-I. flask. The aldehyde distils ofl as rapidly as it is formed and is steam-distilled from the original distillate after rendering it alkaline witlr sodium carbonate. The product is isolated by benzene extraction of the second distillate and distillation under reduced pressure. The yield is 27-35 g- (10-13 per cent of the theoretical amount). 

A mixture of 66.5 g. (0.5 mole) of tetrahydroquinoline and 400 g. of trimethylene chlorobromide (Note 1) is placed in a 1-1. round-bottomed flask attached to a reflux condenser, and heated in an oil bath held at 150-160° for 20 hours (Note 2). The reaction mixture is cooled, a solution of 50 ml. of concentrated hydrochloric acid in 500 ml. of water is added, and the excess trimethylene chlorobromide is removed by distillation with steam (Note 3). The acid residue from the steam distillation is made alkaline with a 40% solution of sodium hydroxide (about 75 ml.), and the julolidine is extracted with two 150-ml. portions of ether. The ethereal solution is washed with ISO ml. of water and dried over sodium hydroxide pellets. The ether is evaporated and the residue distilled under reduced pressure. The portion that boils at 105-110°/ mm. is collected (Notes 4 and 5). The yield is 67-70 g. (77-81%). 

After all the hydrogen peroxide is added, the reaction mixture is allowed to cool to room temperature and is then saturated with sodium chloride, after which it is extracted four times with 100-ml. portions of ether. The combined extracts are dried over sodium sulfate. The ether is removed by distillation on a steam bath, and the residue is then distilled under reduced pressure, Pyrogallol monomethyl ether is collected at 136-138°/22 mm. The yield is 38-44.5 g. (68-80%) of a colorless to light t11ow oil which solidifies on standing (Note 4). 

The ether is removed by dropping the solution slowly from a separatory funnel into a 50-ml. Claisen flask fitted with a condenser for downward distillation and heated on a steam bath (Note 6), and the residual aldehyde is distilled under reduced pressure. The yield of )-tolualdehydc boiling at 90-93 /19 mm. is 10.5-12 g. (62-70%). 

The common methods of purification, discussed below, comprise distillation (including fractional distillation, distillation under reduced pressure, sublimation and steam distillation), crystallisation, extraction, chromatographic and other methods. In some cases, volatile and other impurities can be removed simply by heating. Impurities can also sometimes be eliminated by tbe formation of derivatives from which the purified material is regenerated (see Chapter 2). 

Because phenols are weak acids, they can be freed from neutral impurities by dissolution in aqueous N sodium hydroxide and extraction with a solvent such as diethyl ether, or by steam distillation to remove the non-acidic material. The phenol is recovered by acidification of the aqueous phase with 2N sulfuric acid, and either extracted with ether or steam distilled. In the second case the phenol is extracted from the steam distillate after saturating it with sodium chloride (salting out). A solvent is necessary when large quantities of liquid phenols are purified. The phenol is fractionated by distillation under reduced pressure, preferably in an atmosphere of nitrogen to minimise oxidation. Solid phenols can be crystallised from toluene, petroleum ether or a mixture of these solvents, and can be sublimed under vacuum. Purification can also be effected by fractional crystallisation or zone refining. For further purification of phenols via their acetyl or benzoyl derivatives (vide supra). 

Diethyl malonate [105-53-3] M 160.2, b 92"/22mm, 198-199"/760mm, d 1.056, d s 1.0507, n 1.413. If too impure (IR, NMR) the ester (250g) has been heated on a steam bath for 36h with absolute EtOH (125mL) and cone H2SO4 (75mL), then fractionally distd under reduced pressure. Otherwise fractionally distil under reduced pressure and collect the steady boiling middle fraction. 

---