Cooling deposition

Amino-4 -methylthiazole slowly decomposes on storage to a red viscous mass. It can be stored as the nitrate, which is readily deposited as pink crystals when dilute nitric acid is added to a cold ethanolic solution of the thiazole. The nitrate can be recrystallised from ethanol, although a faint pink colour persists. Alternatively, water can be added dropwise to a boiling suspension of the nitrate in acetone until the solution is just clear charcoal is now added and the solution, when boiled for a short time, filtered and cooled, deposits the colourless crystalline nitrate, m.p. 192-194° (immersed at 185°). The thiazole can be regenerated by decomposing the nitrate with aqueous sodium hydroxide, and extracting the free base with ether as before. 

D. Methionine.—A suspension of 21.5 g. (0.063 mole) of this tricarboxylic acid in 350 cc. of hot water is heated on the steam bath and 40 cc. of concentrated hydrochloric acid (sp. gr. 1.19) is added. Carbon dioxide is immediately evolved and the substance goes into solution. After heating for one and a half hours, 200 cc. more of concentrated hydrochloric acid is added and heating is continued for forty-five minutes longer. The solution, on cooling, deposits phthalic acid this is filtered off and washed with two 50-cc. portions of water (Note 3). The combined filtrate and washings are evaporated to dryness on the steam bath under reduced pressure, and the dry residue is dissolved in... 

The benzene solution is separated and washed twice with 100 cc. of water, once with 200 cc. of 5 per cent potassium hydroxide, and twice with water, and in case the solution is not colorless it is clarified with i g. of Norite. The benzene is removed by distillation and the resulting syrup is dissolved in 300 cc. of alcohol by heating. The solution on cooling deposits cholestanone as well-formed needles. The yield of collected, washed, and air-dried material, m.p. 129-130°, is 41.5-42 g. (83-84 per cent of the theoretical amount). The addition of 80 cc. of water to the filtrate gives about 2 g. of material melting at 125-126°. 

If very pure amine is desired the product described above is dissolved with 1.04 parts of crystalline oxalic acid in eight parts of hot water. After clarification with Norite, the filtered solution on cooling deposits crystals of the acid oxalate. About 5 g. of the salt remains in each 100 cc. of the mother liquor most of this can be obtained by evaporation and further crystallization. The amine is liberated from the pure oxalate with potassium hydroxide, distilled with steam, and purified as described above. When a known amount of amine is desired in water solution (as for optical resolution) a weighed amount of the (anhydrous) oxalate is decomposed and the amine is distilled quantitatively with steam. 

C. Hydrolysis of Ethyl a, fi-Dicyano- -phenyl Propionate — The product thus obtained is hydrolyzed by boiling under a reflux condenser for four hours with 80 cc. of concentrated hydrochloric acid (sp. gr. 1.19). The substance goes into solution and this clear solution, on cooling, deposits phenylsuccinic acid in small crystals which are nearly colorless. These are filtered off, washed with cold water and dried. The yield of product melting at 164-166° is 17.6-18.4 g. (91-95 per cent of the theoretical amount based on the weight of ester used) (Notes 1 and 2). 

About 2 1. of cold water is added to the reaction mixture, and the insoluble material is collected on a Buchner funnel. The precipitate is transferred to a 2-1. beaker and extracted with two 600-cc. portions of hot ethyl alcohol. The combined extracts, on cooling, deposit long needles of stilbene which weigh 55-59 g. and melt at 116-121°. These are filtered with suction and are recrystallized from 600 cc. of 95 per cent ethyl alcohol. The yield is 45-48 g. (53-57 per cent of the theoretical amount) of colorless needles melting at 123-124°. 

In a 5-I. round-bottom flask, fitted with a mechanical stirrer and reflux condenser, are mixed 1150 cc. of water, 840 cc. of commercial sulfuric acid and 700 g. of benzyl cyanide (preparation III, p. 9). The mixture is heated under a reflux condenser and stirred for three hours, cooled slightly and then poured into 2 1. of cold water. The mixture should be stirred so that a solid cake is not formed the phenylacetic acid is then filtered off. This crude material should be melted under water and washed by decantation several times with hot water. These washings, on cooling, deposit a small amount of phenylacetic acid which is filtered off and added to the main portion of material. The last of the hot water is poured off from the material while it is still molten and it is then transferred to a 2-1. Claisen distilling flask and distilled in vacuo. A small amount of water comes over first and is rejected about 20 cc., containing an appreciable amount of benzyl cyanide, then distils. This fraction is used in the next run. The distillate boiling i76-i89°/5o mm. is collected separately and solidifies on standing. It is practically pure phenylacetic acid, m. p. 76-76.5° it amounts to 630 g. (77.5 per cent of the theoretical amount). As the fraction which is returned to the second run of material contains a considerable portion of phenylacetic acid, the yield actually amounts to at least 80 per cent. 

The conversion of the m-monoolefin to its silver nitrate complex 1 was accomplished by adding 1.66 g. (0.010 mole) of the distilled reaction product to a solution of 1.70 g. (0.010 mole) of silver nitrate in 50 ml. of boiling methanol. The resulting solution, when cooled, deposited the complex as white needles, m.p. 79° dec. recrystallization from methanol separated 1.0 g. of the complex, m.p. 80° dec. After this complex had been partitioned between water and ether, the ether phase was separated, dried over magnesium sulfate, and concentrated. Distillation of the residual liquid in a short path still separated 0.45 g. of the pure (Note 6) cfs-cyclodecene, b.p. 70° (1.0 mm.), n B 1.4852. 

The reactions involved in the preparation of ammonium carbamate are essentially either the union of carbon dioxide and ammonia, or the dehydration of ammonium carbonate. A. Basaroff prepared ammonium carbamate by passing the mixture of dried ammonia and carbon dioxide gases into well-cooled absolute alcohol. A copious crystalline precipitate is formed. This is separated by filtration from the mass of liquid, and heated with absolute alcohol in a hermetically sealed vessel to 100°-110° when the liquid on cooling deposits the salt in laminae. These are pressed between filter paper, and dried over potassium hydroxide. A. Mente says the process furnishes a highly pure product, but the cost is high. When the crystals are powdered, they attract moisture from the air, and if the mass is then dried over sulphuric acid or potassium hydroxide, the composition of the product is not quite the same as before. 

Cone, aqua ammonia in the cold dissolves carbamate from the commercial carbonate, and it converts the hydrocarbonate into normal carbonate-either by removing half its carbonic monohydride, or by combining with it and with water. If the commercial carbonate be digested with a sat. soln. of ammonia in a closed vessel at 20° to 25°, this salt slowly dissolves, and the soln., on cooling, deposits crystals of ammonium carbamate and a little normal carbonate (NH3)3H20(C02)2-j-NH3 =H20+2C02(NH3)2. C. Arnold has tabulated the solubilities of the freshly precipitated carbonates and hydroxides of most of the common metals in sat. soln. of potassium and ammonium carbonates. A. Ditte studied the action of soln. of ammonium carbonate on vanadic oxide. 

Tellurium Perchlorate.—By dissolving tellurium dioxide in warm concentrated perchloric acid, a clear solution is obtained which on cooling deposits glistening hexagonal crystals having the composition 2Te02.HC104.7... 

Tellurium dioxide is known in two different crystalline forms. Crystals of the tetragonal system,2 but almost regular (a c — 1 1-1076), of density 5-66, are obtainable from the solution in nitric acid, while the molten dioxide when slowly cooled deposits rhombic needles 3 (a b c=0 4566 1 0-4693) of density 5-93 and identical with the rarely occurring mineral tellurite. 

N-Phenylhydroxylamine (11 g., 0.10 mole)2 (Note 1) and N-phenylmaleimide (17.4 g., 0.10 mole)3 are suspended in 40 ml. of ethanol contained in a 200-ml. Erlenmeyer flask. To the mixture is added immediately (Note 2) 8.98 g. (11.2 ml., 0.124 mole) of freshly distilled w-butyraldehyde. An exothermic reaction ensues, and the mixture spontaneously heats to the boiling point. A clear slightly yellow solution results which, upon cooling, deposits an almost colorless crystalline cake. The mixture is allowed to stand in the ice box for 1 day it is then filtered through a Buchner funnel, and the crystals are washed twice with 25-ml. portions of ice-cold ethanol. The yield of air-dried product, m.p. 99-101°, is 31-32 g. (92-95%). For further purification the crude material is dissolved in 60 ml. of boiling ethanol on the steam bath, and the resulting solution is allowed to cool slowly to room temperature. If crystallization does not spontaneously begin in 5-10 minutes, it can then be induced by... 

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