Vacuum boiling

Alternatively, 63 g (0.45M) BF3 etherate in 180 ml diglyme is added dropwise with stirring to 0.15 M of the indolyglyoxamide and 12 g NaBHi in 300 ml diglyme. Stir 12 hours at room temperature and evaporate in vacuum. Boil residue 2 hours with methanolic NaOH and evaporate in vacuum. Take up residue in ether, wash with water and dry, evaporate in vacuum to get the dialkyltryptamine in ca. 80% yield. 

Uncured adhesives Vapor pressure Toxicity, skin irritation Gassing during vacuum Boiling of low-MW components... 

On a small scale the dissolving and vacuum boiling are carried out in a steam-heated vacuum pan. An advance on this would be to use an open pan to dissolve the sugar and then to feed this to two vacuum pans. The vacuum-cooked mass is then poured onto a cooled metal slab and the mass is turned in on itself to cool the middle (Figure 6.4). Glucose syrup-based boiled sweets form a cool skin on the outside. This means that they can be manipulated by hand. Because of this skin it is necessary to fold the inside of the mass to the outside to cool it. When the mass has cooled sufficiently the colour and flavour may be added and kneaded in,... 

Method 6 (best yield) CPB 19,46(1971), JCS 121,1638(1922) To prepare diethylacetone dicarboxylate (1) proceed as in method 3 for cocaine synthesis, substituting 720 ml ethanol for methanol. To 197 g (I), add rapidly with stirring and cooling 208 g PClj, keeping temperature below 50°. When HCl evolution stops, pour into water and add ice as necessary to cool. Extract the red oil with ether and dry, evaporate in vacuum. Boil residue 2 /2 hours with 20% HCl, evaporate the water and dissolve the residue in ether. Dry and evaporate in vacuum to get 100 g 3-CI-giutaconate (II). 100 g (II), 300 g ethanol, 50 ml sulfuric acid and reflux while passing in ethanol vapor until 1.5 L collects. Add water, extract with ether, wash with aqueous Na carbonate and dry, evaporate in vacuum to get 113 g diethyl-3-CI-glutaconate (III). Mix 28 g NaOH, 140 ml water, 10.4 g hydroxylamine.HCl, 280 ml ethanol and cool to -35° in acetone-dry ice bath. Stir and add 30.3 g (111) in 50 ml ethanol over two minutes stir one hour (can let stand twelve hours). Neutralize with... 

H2S,NH3,HCN and H2O Difficult in operation Incomplete regeneration when stiipping/vacuum (boiling required)... 

Separation of high-molecular-weight heat-sensitive materials. High-molecular-weight materials are often heat sensitive and as such are usually distilled under vacuum to reduce their boiling temperature. 

The distillation continues to a boiling point corresponding an atmospheric boiling point of about 535°C. The remaining material is called vacuum residue. 

When constructing a manometer of the type shown in Fig. 12(c), it is impor tant to apply a very high vacuum (e.g., with a Hy-Vac pump) to the manometer while the mercury in the left-hand (sealed) limb is heated until it boils unless this is done, traces of air will remain in this limb and cause inaccurate readings. During a distillation, the tap I should be kept closed except when a pressure reading is being taken if it is left open indefinitely, a sudden default by the distillation apparatus or by the pump may cause the mercury in the sealed limb of G to fly back and fracture the top of the limb. 

The oxime is freely soluble in water and in most organic liquids. Recrystallise the crude dry product from a minimum of 60-80 petrol or (less suitably) cyclohexane for this purpose first determine approximately, by means of a small-scale test-tube experiment, the minimum proportion of the hot solvent required to dissolve the oxime from about 0-5 g. of the crude material. Then place the bulk of the crude product in a small (100 ml.) round-bottomed or conical flask fitted with a reflux water-condenser, add the required amount of the solvent and boil the mixture on a water-bath. Then turn out the gas, and quickly filter the hot mixture through a fluted filter-paper into a conical flask the sodium chloride remains on the filter, whilst the filtrate on cooling in ice-water deposits the acetoxime as colourless crystals. These, when filtered anddried (either by pressing between drying-paper or by placing in an atmospheric desiccator) have m.p. 60 . Acetoxime sublimes rather readily when exposed to the air, and rapidly when warmed or when placed in a vacuum. Hence the necessity for an atmospheric desiccator for drying purposes. 

The hydrochloride of the amine may be prepared precisely as that of the primary amine. For recrystallisation, boil a suspension of the powdered salt in petroleum (b.p. 60-80°), and then add acetone slowly in small drops until the boiling suspension just becomes clear allow the stirred solution to cool until crystallisation starts, and then chill in ice-water before collecting the colourless plates of the hydrochloride, which after drying in a vacuum desiccator have m.p. 132-134°. 

If a vacuum-distillation apparatus is not available for the above preparation, the crude product may be distilled at atmospheric pressure and the acetoacetate collected as the fraction boiling at i75 -i85 . A pure preparation cannot be obtained in this way, however, because the ester decomposes slightly when distilled at atmospheric pressure. 

Dissolve 8 8 g. (9 0 ml.) of cyclohexanone in 50 ml. of glacial acetic acid, add 8 ml. of phenylhydrazine, and boil the solution under reflux for 5 minutes. Cool the solution, when the tetrahydrocarbazole will crystallise out. Filter at the pump, drain well, and recrystallise either from aqueous ethanol or (better) from aqueous acetic acid. The recrystallisation should be performed rapidly, for the tetrahydrocarbazole undergoes atmO" spheric oxidation in hot solutions after recrystallisation, the compound should be dried in a vacuum desiccator and not in an oven. Repeated recrystallisation should be avoided. The tetrahydrocarbazole, after thorough drying, is obtained as colourless crystals, m.p. 118° yield of recrystallised material, 11 g. 

The best method for removing water (and also solvents of relatively low boiling point) adhering to solids is drying under reduced pressure. A vacuum desiccator is used for this purpose several forms are shown in Fig. II, 38, 1. These are fitted with the exception of ( ) either with... 

---