Cooling dry ice

The checkers transferred cyclopentadiene by using a stainless steel cannula from a cooled (dry ice-methanol), 500-mL, round-bottomed flask to the reaction vessel. 

To a cooled (dry ice-acetone) solution of the methyl pentofuranoside (1.7 g, 10 mmol) in dry pyridine (8 mL) and chloroform (20 mL) was added sulfuryl chloride (4 mL, 30 mmol) dropwise, with stirring. Cooling was continued for an additional 2 h, and then the... 

Excess anhyd ZnBrj (4.5 g, 0.02 mol) was sublimed at 0.1 Torr and dissolved in anhyd Et20 (20 mL). Condensed 2-methylpropene (20 mL) in anhyd EtjO (10 mL) was introduced into a three-neck reaction flask with an attached dry-ice condenser. The solution was stirred and cooled (dry ice). 1,3-Bis(di-azomethyl)benzene (1.23 g, 0.008 mol) in anhyd Et20 (35 mL) and the ethereal ZnBr2 soln were added dropwise simultaneously under an atmosphere of Nj. Decolorization of the bis(diazo) compound was instantaneous at 3-4"C, but only completed over a few seconds at — 20 C. After complete addition, the mixture was stirred for another 30 min and then filtered. The alkene was evaporated at rt, H2O (20 mL) was added, and the organic layer dried (NaOH pellets). After distilling off the solvents, the product was obtained by short-path distillation yield 62 /o bp 80-106°C (bath)/1.5 Torr. 

Phosphorus pentachloride is prepared by the action of chlorine on phosphorus trichloride. To push the equilibrium over to the right, the temperature must be kept low and excess chlorine must be present. Hence the liquid phosphorus trichloride is run dropwise into a flask cooled in ice through which a steady stream of dry chlorine is passed the solid pentachloride deposits at the bottom of the flask. 

Place 0 5 ml. of acetone, 20 ml. of 10% aqueous potassium iodide solution and 8 ml. of 10% aqueous sodium hydroxide solution in a 50 ml. conical flask, and then add 20 ml. of a freshly prepared molar solution of sodium hypochlorite. Well mix the contents of the flask, when the yellow iodoform will begin to separate almost immediately allow the mixture to stand at room temperature for 10 minutes, and then filter at the pump, wash with cold w ater, and drain thoroughly. Yield of Crude material, 1 4 g. Recrystallise the crude iodoform from methylated spirit. For this purpose, place the crude material in a 50 ml. round-bottomed flask fitted with a reflux water-condenser, add a small quantity of methylated spirit, and heat to boiling on a water-bath then add more methylated spirit cautiously down the condenser until all the iodoform has dissolved. Filter the hot solution through a fluted filter-paper directly into a small beaker or conical flask, and then cool in ice-water. The iodoform rapidly crystallises. Filter at the pump, drain thoroughly and dry. 

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 benzene used in this preparation should be reasonably free from toluene therefore use a sample of benzene supplied by dealers as crystalUsable benzene, i.e.y one which crystallises readily when cooled in ice-water. It should preferably be dried over calcium chloride and, immediately before use, filtered through a fluted filter-paper. The pyridine should also preferably be dried over solid potassium hydroxide and redistilled. 

Add 10 g. of the crude hydrazobenzene to 80 ml. of ethanol contained in a flask fitted with a reflux water-condenser. Heat the mixture on a water-bath until the ethanol bolls, and then add 10 g. of zinc dust and 30 ml. of 30% aqueous sodium hydroxide solution. Remove the flask from the water-bath and shake the contents vigorously from time to time. After about 10 minutes, replace the flask on the water-bath and boil the contents for 3-5 minutes. Filter the mixture at the pump, transfer the filtrate to a beaker and cool in ice-water with stirring. The hydrazobenzene separates as colourless crystals, which are filtered off at the pump and drained. A portion when dried in a desiccator has m.p. 124°. 

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°. 

Use the apparatus detailed in Section 111,20. Dissolve 100 g. (123 ml.) of methyl n-butyl ketone (2-hexanone) (Section 111,152) in 750 ml. of ether and add 150 ml. of water. Introduce 69 g. of clean sodium in the form of wire (or small pieces) as rapidly as possible the reaction must be kept under control and, if necessary, the flask must be cooled in ice or in running water. When all the sodium has reacted, separate the ethereal layer, wash it with 25 ml. of dilute hydrochloric acid (1 1), then with water, dry with anhydrous potassium carbonate or with anhydrous calcium sulphate, and distil through a fractionating column. Collect the fraction of b.p. 136-138°. The yield of methyl n-butyl carbinol (2-hexanol) is 97 g. 

Dichlorobutane. Place 22-5g. of redistilled 1 4-butanediol and 3 ml. of dry pyridine in a 500 ml. three necked flask fitted with a reflux condenser, mechanical stirrer and thermometer. Immerse the flask in an ice bath. Add 116 g. (71 ml.) of redistilled thionyl chloride dropwise fix>m a dropping funnel (inserted into the top of the condenser) to the vigorously stirred mixture at such a rate that the temperature remains at 5-10°. When the addition is complete, remove the ice bath, keep the mixture overnight, and then reflux for 3 hours. Cool, add ice water cautiously and extract with ether. Wash the ethereal extract successively with 10 per cent sodium bicarbonate solution and water, dry with anhydrous magnesium sulphate and distil. Collect the 1 4-dichloro-butane at 55-5-56-5°/14 mm. the yield is 35 g. The b.p. under atmospheric pressure is 154 155°. 

Mix 50 ml. of formalin, containing about 37 per cent, of formaldehyde, with 40 ml. of concentrated ammonia solution (sp. gr. 0- 88) in a 200 ml. round-bottomed flask. Insert a two-holed cork or rubber stopper carrying a capillary tube drawn out at the lower end (as for vacuum distillation) and reaching almost to the bottom of the flask, and also a short outlet tube connected through a filter flask to a water pump. Evaporate the contents of the flask as far as possible on a water bath under reduced pressure. Add a further 40 ml. of concentrated ammonia solution and repeat the evaporation. Attach a reflux condenser to the flask, add sufficient absolute ethyl alcohol (about 100 ml.) in small portions to dissolve most of the residue, heat under reflux for a few minutes and filter the hot alcoholic extract, preferably through a hot water fuimel (all flames in the vicinity must be extinguished). When cold, filter the hexamine, wash it with a little absolute alcohol, and dry in the air. The yield is 10 g. Treat the filtrate with an equal volume of dry ether and cool in ice. A fiulher 2 g. of hexamine is obtained. 

Dissolve 2 5 g. of hydroxylamine hydrochloride and 4 g. of crystallised sodium acetate in 10 ml. of water in a small flask or in a test-tube. Warm the solution to about 40° and add 2 5 g. of cyclohexanone. Stopper the vessel securely with a cork and shake vigorously for a few minutes the oxime soon separates as a crystalline solid. Cool in ice, filter the crystals at the pump, and wash with a little cold water. RecrystaUise from light petroleum, b.p. 60-80°, and dry the crystals upon filter paper in the air. The yield of pure cycZohexanone oxime, m.p. 90°, is 2 -5 g. 

Method A. In a 500 ml. round-bottomed flask, fitted with a reflux condenser attached to a gas trap (Fig. II, 13, 8), place 59 g. of succinic acid and 117-5 g. (107-5 ml.) of redistilled acetyl chloride. Reflux the mixture gently upon a water bath until all the acid dissolves (1-2 hours). Allow the solution to cool undisturbed and finally cool in ice. Collect the succinic anhydride, which separates in beautiful crystals, on a Buchner or sintered glass funnel, wash it with two 40 ml. portions of anhydrous ether, and dry in a vacuum desiccator. The yield of succinic anhydride, m.p. 118-119°, is 47 g. 

Method B. In a 500 ml. round-bottomed flask, provided with a reflux condenser protected by a cotton wool (or calcium chloride) drying tube, place 59 g. of succinic acid and 102 g. (94-5 ml.) of redistilled acetic anhydride. Reflux the mixture gently on a water bath with occasional shaking until a clear solution is obtamed ca. 1 hour), and then for a further hour to ensure the completeness of the reaction. Remove the complete assembly from the water bath, allow it to cool (observe the formation of crystals), and finally cool in ice. Collect the succinic anhydride as in Method A. The yield is 45 g., m.p. 119-120°. 

Place 200 g, (250 ml.) of rectified spirit in a 1-litre round-bottomed flask fitted with a reflux condenser. Cool in ice and run in, slowly and with frequent shaking, 200 g. (109 ml.) of concentrated sulphuric acid. Add 83 g. (104 ml.) of -butyl cyanide (Section 111,113) to the mixture and reflux the whole for 10 hours. Allow to cool, pour the reaction mixture into ice water, separate the upper layer of ester and alcohol, and dry over anhydrous magnesium or calcium sulphate. Distil through a fractionating column and collect the ethyl n-valerate at 143-146°. A further amovmt of the pure ester may be obtained by redrying the fraction of low boiling point and redistilling. The yield is 110 g. 

Place 125 ml. of concentrated ammonia solution (sp. gr. 0-88) in a 600 ml. beaker and surround the latter with crushed ice. Stir the ammonia solution mechanically, and introduce the n-caproyl chloride slowly by means of a suitably supported separatory funnel with bent stem. The rate of addition must be adjusted so that no white fumes are lost. The amide separates immediately. Allow to stand in the ice water for 15 minutes after all the acid chloride has been introduced. Filter oflF the amide at the pump use the flltrate to assist the transfer of any amide remaining in the beaker to the Alter (2). Spread the amide on sheets of Alter or drying paper to dry in the air. The crude n-capro-amide (30 g.) has m.p. 98-99° and is sufficiently pure for conversion into the nitrile (Section 111,112) (3). Recrystallise a small quantity of the amide by dissolving it in the minimum volume of hot water and allowing the solution to cool dry on filter paper in the air. Pure n-caproamide has m.p. 100°. 

N-Nitrosodiethylamine. Add 36-5 g. (51-5 ml.) of diethylamine slowly to the calculated quantity of carefully standardised 5A-hydra chloric acid cooled in ice (1). Introduce the solution of the hydi ochloride into a solution of 39 g. of sodium nitrite (assumed to be of 90 per cent, purity) in 45 ml. of water contained in a 250 ml. distilling flask. Distil the mixture rapidly to dryness. Separate the yellow upper layer of the nitrosamine from the distillate saturate the aqueous layer with soUd potassium carbonate and remove the nitroso compound which separates and add it to the main product. Dry over anhydrous potassium carbonate and distil. Collect the diethylnitrosamine at 172-173-5°, The yield is 41 g. 

Mix together in a 250 ml. flask carrying a reflux condenser and a calcium chloride drying tube 25 g. (32 ml.) of freshly-distilled acetaldehyde with a solution of 59-5 g. of dry, powdered malonic acid (Section 111,157) in 67 g. (68-5 ml.) of dry pyridine to which 0-5 ml. of piperidine has been added. Leave in an ice chest or refrigerator for 24 hours. Warm the mixture on a steam bath until the evolution of carbon dioxide ceases. Cool in ice, add 60 ml. of 1 1 sulphuric acid (by volume) and leave in the ice bath for 3-4 hours. Collect the crude crotonic acid (ca. 27 g.) which has separated by suction filtration. Extract the mother liquor with three 25 ml. portions of ether, dry the ethereal extract, and evaporate the ether the residual crude acid weighs 6 g. Recrystallise from light petroleum, b.p. 60-80° the yield of erude crotonic acid, m.p. 72°, is 20 g. 

Into a 500 ml. round-bottomed flask, fitted with a reflux condenser, place 42 g. of potassium hydroxide pellets and 120 g. (152 ml.) of absolute ethyl alcohol. Heat under reflux for 1 hour. Allow to cool and decant the liquid from the residual solid into another dry 500 ml. flask add 57 g. (45 ml.) of A.R. carbon dtsulphide slowly and with constant shaking. Filter the resulting almost solid mass, after cooling in ice, on a sintered glass funnel at the pump, and wash it with two 25 ml. portions of ether (sp. gr. 0-720), followed by 25 ml. of anhydrous ether. Dry the potassium ethyl xanthate in a vacuum desiccator over silica gel. The yield is 74 g. If desired, it ma be recrystallised from absolute ethyl alcohol, but this is usually unneceasary. 

Place a mixture of 1 0 g. of the hydrocarbon, 10 ml. of dry methylene chloride or ethylene dichloride or syw.-tetrachloroethane, 2 5 g. of powdered anhydrous aluminium chloride and 1-2 g. of pure phthalic anhydride in a 50 ml. round-bottomed flask fitted with a short reflux condenser. Heat on a water bath for 30 minutes (or until no more hydrogen chloride fumes are evolved), and then cool in ice. Add 10 ml. of concentrated hydrochloric acid cautiously and shake the flask gently for 5 min utes. Filter oflf the solid at the pump and wash it with 10-15 ml. of cold water. Boil the resulting crude aroylbenzoic acid with 10 ml. of 2 -5N sodium carbonate solution and 0 2 g. of decolourising carbon for 5 minutes, and filter the hot solution. Cool, add about 10 g. of crushed ice and acidify... 

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