Distillation, formaldehyde solutions Pressure

Ethyl propane-1 1 3 3-tetracarboxylate. Cool a mixture of 320 g. (302 ml.) of redistilled diethyl malonate and 80 g. of 40 per cent, formaldehyde solution ( formalin ) contained in a 1-htre round-bottomed flask to 5° by immersion in ice, and add 5 g. (7 ml.) of diethylamine. Keep the mixture at room temperature for 15 hours and then heat under a reflux condenser on a boiling water bath for 6 hours. Separate the aqueous layer, dry the organic layer with anhydrous magnesium sulphate, and distil under reduced pressure. Collect the ethyl 1 1 3 3-tetracarboxylate at 200-215°/20 mm. The yield is 250 g. 

A mixture of 106 g. (1.0 mole) of p-xylene, 530 g. of concentrated hydrochloric acid, and 106 g. (1.27 moles of CH2O) of 37% aqueous formaldehyde solution (formalin) is stirred and held at 60-70° for 7 hours while a stream of hydrogen chloride is introduced into the reaction mixture. Hood.) The oily layer is removed by ether extraction, and after drying the ether is removed by distillation. The residual oil is distilled at reduced pressure, and 106 g. (69%) of product is obtained at 103-112°/14 mm. Redistillation of this fraction gives a small fore-run followed by most of the material boiling at 100-103°/12 mm. 

Four milliliters of 1 AT aqueous sodium hydroxide solution is added to a mixture of 300 g. (5.2 moles) of acetone and 100 g. (0.86 mole) of aqueous 35% formaldehyde solution. The mixture is held at room temperature for 3-4 hours and then neutralized with 4 ml. oi 1 N hydrochloric acid. The excess acetone is distilled off on a water bath heated to 80-85°, and 2-4 g. of anhydrous zinc chloride is added to the residue. The mixture is distilled on an oil bath, and the distillate is collected as long as it comes over colorless. The distillate is treated with potassium carbonate, and the organic material is separated and dried over sodium sulfate. Distillation at 130 mm. pressure gives a 25-35% yield of methyl vinyl ketone boiling at 33-34°. Some decomposition occurs if the distillation is carried out at atmospheric pressure, where the product boils at 80°. 

Tetra-(chloromethyl)-phosphonium chloride (5 g) in 20 mL water was treated with 8 g sodium bicarbonate. The solution became milky and gave a strong formaldehyde reaction with fusion reagent. The phosphine was shaken out with carbon bisulfide, dried over sodium sulfate, and distilled under diminished pressure b.p. 100°C (7 mmHg). While heated at atmospheric pressure, tri-(chloromethyl)phosphine decomposes. It is a colorless, mobile liquid with a powerful, benumbing odor and with slight solubility in water. 

Korzhev and Rossinska> a mea iired partial-pressure values for formaldehyde solutions at ordiumu temperatures by analysing the formaldehyde oouTcnt of the condensate obtained b.y distilling solutions of knovn concentrations at reduced pressures. Tlie A ahies they obtained at these temperatures are higher tlian those of Ledbury and Blair. 

Tile bella iur of fomialdelivde. Solutions on distillation under various conditions of temperature and pressure indicates that the partial pi-essure of formaldehyde over these solutions Ls in reality the decomposition pres-sure of dissolved foimaldehyde hydrate-h AVitli the aid of this concept it Is possible to predict the bdiavior of aqueous formaldehyde solutions under various conditions and devise methods for the l eco en or imioval of formaldehyde from these systems Solutions containing components other than formaldehyde and water can prolialily be handled in a sunilar fashion, pro-vdded these components do not react with fomialdchyde under the conditioas stipulated. 

Pressure Distillation., hen formaldehyde solutions ai e subjected to pressure di.< tillatioii, the fonnaldehyde passes 0 er in the first fraction. distilled and distillates of higher concentration than the oiiginal solution are obtained. This effect i. illustrated by the data of Ledbuiy and Blair who employed pressure distillation for the recovery of formaldehyde from... 

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. 

Hexagonal polyoxymethylene of polydispersity 1 and h h molecular weight can also be prepared in methanol instead of water. The equilibria are analogous to those in the aqueous system. Basic catalysts are also preferred in this system. The polymerization is best carried out at 110°C and a highly concentrated solution of 85% formaldehyde can be used. Under these conditions the polymerization must be carried out under pressure, and the methanol is distilled overhead while new formaldehyde is added. Small amounts of water in the system induced side reactions, mainly the formation of methyl formate. In one reported run 22% of polyoxymethylene of a molecular weight M of 46,000 was obtained after 90 h. The loss of formaldehyde by side reactions was less than 1%. 

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