Steam/water distillation

A solution of 387 g. (3.0 moles) of isoquinoline in 350 ml. of 48% hydrobromic acid is evaporated to near dryness, and 480 g. (3.0 moles) of bromine is added slowly. (Hood.) The resulting mixture is heated under an air reflux condenser at 180-190° for 7 hours, during which evolution of hydrogen bromide is complete. After cooling, excess sodium hydroxide solution is added and the mixture is steam-distilled. Water is decanted from the distillate until approximately 5 1. remains, and nitric acid is added to the hot mixture until the bromoisoquinoline is in solution. Upon cooling the nitrate salt precipitates and is filtered off and redissolved in hot water. Addition of excess ammonium hydroxide precipitates the 4-bromoisoquinoline which upon recrystallization from ether melts at 39-40°. The yield varies between 45% and 74%. 

Historically three types of distillation have been used water distillation, water-steam distillation, and steam distillation. Water distillation is sometimes referred to as indirect steam distillation. In this method, plant material is soaked in water... 

Methanol and acetonitrile are HPLC grade. Steam distilled water is used for all reagent preparation. All reagents are stored at room temperature unless otherwise indicated. 

To purify furfural by the process of steam distillation, water is added to impure furfural and the two-phase mixture is boiled. If the impurities do not change the boiling temperature very much, the two-phase mixture boils near 97.9°C at 1.000 atm. The vapor has a furfural mole fraction equal to 0.092. The vapor is condensed to two liquid phases, and the furfural layer is recovered and dried. At 20 C, this layer has a furfural mole fraction of 0.78 before drying. The advantage of steam distillation is that it can be carried out at a lower temperature than an ordinary distillation. The higher temperature of an ordinary distillation might decompose the organic substance. 

Steam-distillation. Many water-insoluble compounds, both solid and liquid, may be readily purified by distillation in a... 

The material to be steam-distilled (mixed with some water if a solid compound, but not otherwise) is placed in C, and a vigorous current of steam blown in from D. The mixture in C is thus rapidly heated, and the vapour of the organic compound mixed with steam passes over and is condensed in E. For distillations on a small scale it is not necessary to heat C if, however, the flask C contains a large volume of material or material which requires prolonged distillation, it should be heated by a Bunsen burner, otherwise the steady condensation of steam in C will produce too great a volume of liquid. 

If the organic compound which is being steam-distilled is freely soluble in water, an aqueous solution will ultimately collect in the receiver F, and the compound must then be isolated by ether extraction, etc. Alternatively, a water-insoluble compound, if liquid, will form a separate layer in F, or if solid, will probably ciystallise in the aqueous distillate. When steam-distilling a solid product, it is sometimes found that the distilled material crystallises in E, and may tend to choke up the condenser, in such cases, the water should be run out of the condenser for a few minutes until the solid material has melted and been carried by the steam down into the receiver. 

Steam Distillatioo. A compact and efficient apparatus is shown in Fig, 43. The liquid to be steam-distilled is placed in the tube A and water is placed in the outer flask B. On heating B, steam passes into the inner tube A through the inlet tube C, and steam-volatile compounds are rapidly distilled and collected in the receiver placed at the end of the condenser D. 

A very suitable apparatus for semi-micro steam-distillation, particularly for suspensions that are likely to bump badly, is showm in Fig. 44. This consists of a 50 ml. Kjeldahl flask, clamped at an angle of 45°, and fitted with a long glass tube for the inlet of steam. The Outlet-tube is bent twice, first at 135° and then at 45° as shown, and fitted into a small water-condenser. 

A considerable amount of the formic acid, however, still remains behind in the distilling-flask as the unhydrolysed monoformate. Therefore, if time allows, dilute the residue in the flask with about an equal volume of water, and then steam-distil, the monoformate ester being thus completely hydrolysed and the formic acid then driven over in the steam. Collect about 400 ml. of distillate. Add this distillate to that obtained by direct heating of the reaction mixture and then treat with lead carbonate as described above. Total yield of lead formate is now about 40 g. 

Prepare a mixture of 25 ml. of concentrated nitric acid and 80 ml. of water in a 750 ml. flat-bottomed flask for which a steam-distillation fitting is available for subsequent use. Warm a mixture of 20 g. of phenol and 15 ml. of water gently in a small conical flask until the phenol is molten on shaking the... 

Then, while the diazonium solution is standing in ice-water, dissolve 55 g. of powdered copper sulphate (CuS04,5Ha0) in 200 ml. of water contained in a 1500 ml. flat-bottomed flask, for which a steam-distillation fitting is available for subsequent use. Place a thermometer in the copper sulphate solution and warm the latter to 60-65 . Now cautiously add a solution of 60 g. of powdered potassium cyanide in too ml. of water to the copper... 

Now add the diazonium solution to the potassium cupro-cyanide in small quantities at a time so that the temperature of the mixture remains between 60° and 70° shake the mixture vigorously after each addition of the diazo solution. Then fit a reflux air- or water-condenser to the flask, and heat the latter on a boiling water-bath for 15 minutes to complete the reaction. Finally steam-distil the solution until no more oily benzonitrile passes over (usually until about 600 ml. of distillate have been collected). 

Pour the mixture into a 500 ml. flask fitted with a steam-distillation head, and with a steam-inlet tube reaching almost to the bottom of the flask. First distil off the benzene in steam. Then place the flask in an oil-bath heated to 165-170 ", and continue the steam-distillation (2-3 hours). The /)-bromobiphenyl passes over and forms orange crystals in the water-condenser therefore run the water out of the condenser for a short while from time to time to melt the orange deposit and allow it to run into the receiver containing the distilled water. 

Prepare a mixture of 30 ml, of aniline, 8 g. of o-chloro-benzoic acid, 8 g. of anhydrous potassium carbonate and 0 4 g. of copper oxide in a 500 ml. round-bottomed flask fitted with an air-condenser, and then boil the mixture under reflux for 1 5 hours the mixture tends to foam during the earlier part of the heating owing to the evolution of carbon dioxide, and hence the large flask is used. When the heating has been completed, fit the flask with a steam-distillation head, and stcam-distil the crude product until all the excess of aniline has been removed. The residual solution now contains the potassium. V-phenylanthrani-late add ca. 2 g. of animal charcoal to this solution, boil for about 5 minutes, and filter hot. Add dilute hydrochloric acid (1 1 by volume) to the filtrate until no further precipitation occurs, and then cool in ice-water with stirring. Filter otT the. V-phcnylanthranilic acid at the pump, wash with water, drain and dry. Yield, 9-9 5 g. I he acid may be recrystallised from aqueous ethanol, or methylated spirit, with addition of charcoal if necessary, and is obtained as colourless crystals, m.p. 185-186°. 

Cool the solution thoroughly in ice-water, and then make it alkaline by the cautious addition (with stirring or shaking) of a solution of 80 g. of sodium hydroxide in ca, 150 ml. of water. Now isolate the free tertiary amine by steam-distillation into hydrochloric acid, etc., precisely as for the primary amine in Stage (D), but preferably using a smaller flask for the final distillation. Collect the 2-dimethylamino- -octane, b.p. 76-78715 mm. Yield, 13-14 g. At atmospheric pressure the amine has b.p. 187-188°. 

Fit securely to the lower end of the condenser (as a receiver) a Buchner flask, the side-tube carrying a piece of rubber tubing which falls well below the level of the bench. Steam-distil the ethereal mixture for about 30 minutes discard the distillate, which contains the ether, possibly a trace of unchanged ethyl benzoate, and also any biphenyl, CeHs CgHs, which has been formed. The residue in the flask contains the triphenyl carbinol, which solidifies when the liquid is cooled. Filter this residual product at the pump, wash the triphenyl-carbinol thoroughly with water, drain, and then dry by pressing between several layers of thick drying-paper. Yield of crude dry product, 8 g. The triphenyl-carbinol can be recrystallised from methylated spirit (yield, 6 g.), or, if quite dry, from benzene, and so obtained as colourless crystals, m.p. 162. ... 

Cool the flask in ice-water and pour the ethereal solution into a mixture of about 6 ml. of dil. H2SO4 and 10 g. of crushed ice contained in a 50 ml. flask fitted for steam-distillation, taking care to leave behind any unchanged magnesium. Fit to the lower end of the condenser a small Buchner flask or boiling-tube with side-arm (45°) carrying a piece of rubber tubing which falls well below the level of the bench. 

Steam-distil the ethereal solution and discard the distillate. The residue in the flask is triphenyl-carbinol and solidifies on cooling. Filter at the pump, wash with water, drain and dry. Yield of crude product 0 6 g. Recrystallise when dry from benzene to obtain colourless crystals m.p. 162°. 

The mixed bases are boiled with an acetic acid-acetic anhydride mixture to convert the aniline into acetanilide. The product is poured into water, when the acetanilide crystallises out while the quinoline remains in solution as quinoline acetate. The acetanilide is filtered off, and the filtrate made alkaline and steam-distilled. 

The mixed amines are dissolved in hydrochloric acid and zinc chloride solution added. The quinoline chlorozincate, (C H7N)2,HtZnCl, crystallises out, being almost insoluble in water, while the aniline chlorozincate remains in solution. The quinoline chlorozincate is then filtered off and decomposed by alkalis, and the liberated quinoline extracted with ether or steam-distilled. 

The reaction is carried out in a 2-litre long-necked round-bottomed flask, to which is fitted an efficient reflux water-condenser, capable of condensing a sudden rush of vapour without choking. For this purpose, a long bulb-condenser, similar to that shown in Fig. 3(A) (p. 9) is best, but the inner tube must be of wide bore (at least 12 mm.). Alternatively, an air-condenser of wide bore may be used, an.d a short double-surface water-condenser fitted to its top. A steam-distillation fitting for the flask should also be prepared in advance, so that the crude product can subsequently be steam-distilled directly from the flask. The glj cerol used in the preparation must be anhydrous, and should therefore be dehydrated by the method described on p. 113. 

The reaction is best carried out in the apparatus used in the preparation of quinoline, a 1500 ml. flask being fitted with a wide-bore air-condenser carrying in turn a water-condenser a still-head to fit the flask for subsequent steam-distillation should be assembled in advance. 

---