Discontinuous Vacuum Drying

Jomaa, W. and Baixeras, O., 1997. Discontinuous vacuum drying of oakwood Modelling and experimental investigations, Drying Technol., 15 2129-2144. 

Catalyst A mixture of 5.26 g of rhodium chloride trihydrate, 0.34 g of palladium chloride, 18 g of carbon (Darco G-60), and 200 ml of water is rapidly stirred and heated to 80°. A solution of lithium hydroxide hydrate (2.7 g) in 10 ml of water is added in one portion and the heating discontinued. Stirring is continued overnight, after which the mixture is filtered and washed with 100 ml of 0.5 % aqueous acetic acid. The product is dried in a vacuum oven at 65°. About 20 g of the catalyst is thus obtained. 

A mixture of acetamide (30 g. = 0-5 mole) and bromine (80 g. = 26 c.c.) in a half-litre flask is kept well cooled with water while enough of a solution of 50 g. of potassium hydroxide in 350 c.c. of water is added to change the initially red-brown colour into a pale yellow this requires most of the alkali. The solution is now run from a dropping funnel in an unbroken jet into a solution of 80 g. of potassium hydroxide in 150 c.c. of water, maintained at 70°-75° in a litre flask. The operation lasts for several minutes. Until the reaction mixture becomes colourless (one quarter to half an hour) the temperature is maintained at 70°-75°, and then the methylamine is distilled with steam. An adapter is fixed to the lower end of the condenser and dips 1 cm. below the surface of the liquid in the receiver (100 c.c. of approximately 5 N-hydrochloric acid2). As soon as the liquid which forms in the condenser is no longer alkaline the distillation is discontinued and the contents of the receiver are evaporated to dryness in a porcelain basin on the water bath. The last traces of water are removed by allowing the basin to stand over night in a vacuum desiccator. The dried material is boiled with absolute alcohol, which dissolves the methylamine hydrochloride but not the ammonium chloride with which it is mixed. The clear filtrate obtained when the ammonium chloride is removed by filtration is concentrated to a small volume and the methylamine hydrochloride is allowed to crystallise out in the cold. The salt is filtered with suction, washed with a little alcohol, and dried in a desiccator. Yield 15-20 g. 

C. (R,R)-N,N -Bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine. A 2-L, three-necked, round-bottomed flask equipped with a mechanical overhead stirrer, reflux condenser, and an addition funnel is charged with 29.7 g of (R,R)-1,2-diammoniumcyclohexane mono-(+)-tartrate salt (0.112 mol), 31.2 g of potassium carbonate (0.225 mol, 2 eq), and 150 mL of water. The mixture is stirred until dissolution is achieved, and 600 mL of ethanol is added. The cloudy mixture is heated to reflux with a heating mantle and a solution of 53.7 g (0.229 mol, 2.0 eq) of 3,5-di-tert-butylsalicylaldehyde in 250 mL of ethanol is then added in a slow stream over 30 min (Note 19). The addition funnel is rinsed with 50 mL of ethanol and the mixture is stirred at reflux for 2 hr before heating is discontinued. Water, 150 mL, is added and the stirred mixture is cooled to <5°C over 2 hr and maintained at that temperature for another hour. The yellow solid is collected by vacuum filtration and washed with 100 mL of ethanol. After the solid is air dried, it is dissolved in 500 mL of methylene chloride. The organic solution is washed with 2 x 300 mL of water, followed by 300 mL of saturated aqueous sodium chloride. The organic layer is dried over sodium sulfate, and filtered to remove the drying agent. The solvent is removed by rotary evaporation to yield the product as a yellow solid, mp 200-203°C (Notes 20 and 21). 

A soil infiltration test was devised to screen a large number of compounds within a limited time span. The amounts used are far in excess of quantities used in field application. A 5% diamide solution in isopropanol, 15 mL, was added to 50 g soil, air dried overnight, and then placed in a vacuum oven at 50° for 1 hr to remove traces of isopropanol. The treated soil, 10 g, was placed in a 25 X 500 mm glass chromatographic column with a coarse porosity fritted disc on top of a detachable adapter base. The soil was tapped down lightly with a wooden dowel to a depth of 12 mm in order to prevent channeling. Forty-five cm of water covered the soil. The period required for 200 ml distilled water to penetrate through 10 g of treated soil was recorded as the infiltration time. The test was arbitrarily discontinued after 2 weeks. 

Effect of Ammonia. a,a,a-TRiCHLOROTOLUENE (VIII). A dry stream of gaseous ammonia was passed for 4 hours into 19.6 grams of VIII (0.1 mole) at room temperature. Within 5 minutes, the originally colorless, transparent liquid became slightly turbid, but no heat evolution was noticeable. The introduction of ammonia was discontinued and the reaction contents were subjected to vacuum distillation. The entire reaction yielded only one component which was identified as unchanged VIII. Of the two boiling points, b.p.23 110.7° C. (18) and b.p.25 105° C. (19), cited in the literature, the one found in this distillation agrees with the latter. The experimental refractive index, was 1.5573 and is consistent with the literature value (5). 

Dry carbon dioxide gas is bubbled slowly under the surface of a cooled tetrahydrofnran solution of one mole of benzylmagnesium chloride complex until a negative Gilman Schultze color test results. The mixture is then heated to reflux, the addition of carbon dioxide is discontinued, and a further one mole of benzylmagnesium chloride complex is added rapidly (over a period of 20-40 minutes). After completion of addition, the mix is refluxed for 2-4 hours, cooled, and 100-200 mL. of toluene added. The organic solution and suspension is extracted by one 100-mL. portion of water and one 100-mL. portion of 10% sodium carbonate. On acidification of the aqueous extracts, phenylacetic acid is obtained. The organic layer is subjected to distillation to remove solvents and then to vacuum distillation. Dibenzyl ketone and a small amount of tribenzyl carbinol are obtained. 

At the end of two hours, the heating was discontinued and about 500 mL. of hot water was added to the mixture. The mixture was acidified with concentrated hydrochloric acid and was then extracted three times with about 250 mL. of benzene and the combined extract was washed with water. The benzene was removed by distillation and the solid product was dried in a vacuum oven and weighed. The yield was 106.9 g of 3,4,5-trimethoxybenzaldehyde, representing a yield of 99.3% of the theoretical. Analysis by gas-liquid chromatography (g.l.c.) showed a purity of 99.85% with syringaldehyde as the only detectable impurity. 

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