Acidity continued hydrogen cyanide

A solution of sodium cyanide [143-33-9] (ca 25%) in water is heated to 65—70°C in a stainless steel reaction vessel. An aqueous solution of sodium chloroacetate [3926-62-3] is then added slowly with stirring. The temperature must not exceed 90°C. Stirring is maintained at this temperature for one hour. Particular care must be taken to ensure that the hydrogen cyanide, which is formed continuously in small amounts, is trapped and neutrali2ed. The solution of sodium cyanoacetate [1071 -36-9] is concentrated by evaporation under vacuum and then transferred to a glass-lined reaction vessel for hydrolysis of the cyano group and esterification. The alcohol and mineral acid (weight ratio 1 2 to 1 3) are introduced in such a manner that the temperature does not rise above 60—80°C. For each mole of ester, ca 1.2 moles of alcohol are added. 

Production of cyanohydrins is accompHshed through the base-cataly2ed combination of hydrogen cyanide and the carbonyl compound in a solvent, usually the cyanohydrin itself (17). The reaction is carried out at high dilution of the feeds, at 10—15°C, and pH 6.5—7.5. The product is continuously removed from the reaction 2one, cooled to push the equilibrium toward cyanohydrin formation, and then stabili2ed with mineral acid. Purification is usually effected by distillation. 

In a typical process adiponitrile is formed by the interaction of adipic acid and gaseous ammonia in the presence of a boron phosphate catalyst at 305-350°C. The adiponitrile is purified and then subjected to continuous hydrogenation at 130°C and 4000 Ibf/in (28 MPa) pressure in the presence of excess ammonia and a cobalt catalyst. By-products such as hexamethyleneimine are formed but the quantity produced is minimized by the use of excess ammonia. Pure hexamethylenediamine (boiling point 90-92°C at 14mmHg pressure, melting point 39°C) is obtained by distillation, Hexamethylenediamine is also prepared commercially from butadience. The butadiene feedstock is of relatively low cost but it does use substantial quantities of hydrogen cyanide. The process developed by Du Pont may be given schematically as ... 

Esterification of Hexacyanoferric(II) Acid. When hexacyanoferric (II) acid is heated with ethyl alcohol, esterification of the acid takes place (15, 21). The initial partially esterified hexacyanoferric (II) acid polymerizes with the evolution of hydrogen cyanide or is further esterified. Both reactions appear to take place concurrently. Addition of hydrogen cyanide to the reaction mixture causes liberation of ethyl isonitrile from the complex. Hence it is possible to synthesize isonitriles on a continuous basis—i.e., esterification of the strong hexacyanoferric (II) acid, replacement of the isonitrile in the complex by hydrogen cyanide, re-esterification, etc. (15). The over-all reaction is complex, and the precise course of the reaction has not been elucidated. 

One of the separatory funnels is filled with 1 1. of sulfuric acid prepared by the careful addition of 392 g. (4 moles) (213 cc.) of concentrated sulfuric acid to 213 cc. of water. The other separatory funnel is filled with a solution of 203 g. of commercial sodium cyanide (about 96 per cent) (4 moles) dissolved in sufficient water to make 500 cc. of solution. Evolution of hydrogen cyanide takes place on the simultaneous addition of the two solutions. Practically all of the reaction occurs in the funnel, F, and the sodium bisulfate solution continuously drains into the flask so that fresh solutions are always present. The solution in the funnel remains clear as long as sufficient sulfuric acid is present. An excess of sodium cyanide colors the solution yellow and leads to the formation of a muddy brown precipitate. By adjusting the flow of solutions the rate of evolution is easily controlled, and the preparation requires no attention beyond that involved in the occasional replenishment of the solutions in the separatory funnels. The last part of the hydrogen cyanide can be driven from the apparatus by boiling the bisulfate solution for a few minutes. The yield of acid melting at — r5° to — r4.5° is roo-ro5 g. (93-97 per cent of the theoretical amount) (Notes 3 and 4). 

A mixture of 288 g (4 mols) of isobutyraldehyde, 288 g of methanol was cooled to 10°C and 170 g (2 mols) of 36.6% formalin containing 8.5 g (3% based on isobutyraldehyde) of sodium hydroxide was added dropwise over a 55 minute period to produce alpha,alpha-dimethyl-beta-hydroxy-propionaldehyde. The mixture was stirred for an additional 2 hours at 10-15°C and then contacted with acetic acid to neutralize the catalyst. The excess isobutyraldehyde and methanol were stripped off at a kettle temperature of 50°C at 25 mm. To the residual a,a-dimethyl-beta-hydroxypropionaldehyde a mixture of 260 ml of methanol and 2 g (0.75%) sodium cyanide was added and the solution cooled to 10°C before adding 59.4 g (2.2 mols) of hydrogen cyanide dropwise over a 35 minute period to produce a,y-dihydroxy-p,p-dimethylbutyronitrile. The mixture was stirred at 10°C for one hour period and then contacted with acetic acid to neutralize the catalyst before stripping off the excess methanol to a kettle temperature of 45°C at 18 mm. The crude cyanohydrin was then hydrolysed by heating with 4 mols of concentrated hydrochloric acid at 80°C for 2 hours, then diluting with an equal volume of water and heating at 100°C for an additional 8 hours. The aqueous mixture was extracted continuously with ethylene dichloride. The solvent was... 

Methyl methacrylate (melting point -48°C, boiling point 100°C, density 0.9394, flash point 9°C) is produced by the acetone cyanohydrin process in which the acetone cyanohydrin (from the reaction of acetone with hydrogen cyanide, q.v.) is reacted with sulfuric acid to yield methacrylamide sulfate, which is further hydrolyzed and esterified. The process is continuous. 

Cyanomethylbenzoic acid. This preparation must be conducted in an efficient fitme cupboard. Into a 1-litre three-necked flask, provided with a mechanical stirrer and a thermometer, place 40 g (0.33 mol) of phthalide and 40 g (0.615 mol) of powdered potassium cyanide (CAUTION). Heat the stirred mixture to 180-190 °C (internal temperature) in an oil bath for 4-5 hours. Allow to cool, add 400 ml of distilled water and stir the mixture until all the solids are dissolved (about 1 hour). Filter off any unreacted phthalide. Add dilute hydrochloric acid (1 1) to the dark aqueous solution (CAUTION hydrogen cyanide is evolved) until it becomes turbid (about 20 ml are required), and continue the addition until the solution is slightly acid filter off any dark impurities which may separate. Neutralise the solution carefully with sodium hydrogen carbonate, add a few grams of decolourising carbon, stir the mixture for several minutes and filter. Acidify the nearly colourless filtrate with about 20 ml of concentrated hydrochloric acid, cool in ice and filter at the pump. The resulting o-cyanomethylbenzoic acid (36 g) melts at... 

Continued passage of carbon dioxide through a boiling solution of potassium ferricyanide results in the precipitation of ferric hydroxide and the formation of potassium carbonate and hydrogen cyanide or its decomposition products, ammonia and formic acid.5... 

If, on the other hand, the free acid or base is removed in some manner, the extent of hydrolysis of the salt must increase in order to maintain the hydrolytic equilibrium. For example, if a solution of potassium cyanide is heated or if a current of air is passed through it, the hydrogen cyanide formed by hydrolysis can be volatilized as it is removed, however, more is regenerated by the continued hydrolysis of the potassium cyanide. When a solution of ferric chloride is heated, the hydrogen chloride is removed and hence the hydrolytic process continues the hydrated ferric oxide which is formed remains in colloidal solution and imparts a dark brown color to the system. 

Olefins, addition—Continued of diazoacetic ester, 498 of halo ethers, 232 of halogen, 106 of hydrogen cyanide, 603 of hydrogen halide, 105 of hypohalous acid, 109 of polyhalides, 107 to cyanides, 571 allylic bromination, 36, 104 condensation, with halides, 108 with phenols, 179 conversion to amides (Wi 11 gerodt),... 

Edetic acid may also be prepared by the reaction of ethylenediamine with hydrogen cyanide and formaldehyde with subsequent hydrolysis of the tetranitrile, or under alkaline conditions with continuous extraction of ammonia. 

Purification this step features the second innovation of the process which, to eliminate the by-product acrolein, favors the formation of cyanohydrin by means of the hydrogen cyanide which is also present This operation takes place at low temperature (20 Q in agitated reactors, either continuously in the presence of a copper-based catalyst, or semi-continuously with a reaction phase in basic medium (caustic soda addition), followed by a neutralization period (sulfuric acid addition). The cyanohydrin obtained is then removed by vacuum distillation. The withdrawal may be sent to a thin layer evaporator to recover entrained acrylonitrile. These treatments must be conducted in the presence of a polymerization inhibitor and at a temperature below 55 C to prevent the rede-composition of cyanohydrin.... .. ... 

Esters of methacrylic acid are obtained directly from acetone cyanohydrin by reaction of the latter with concentrated sulfuric acid to give methacrylamide sulfate, followed by reaction with an alcohol. The process is continuous and the methacrylamide sulfate is not isolated. Acetone cyanohydrin is derived from acetone and hydrogen cyanide (Pig. 15-39), Polymerization Procedures. Of particular importmice to the acrylics is the cast or bulk method of polymerization. This method is employed to produce cast polymethyl methacrylate sheets which are widely used in industrial applications. Careful control of polymerization is required to obtain a bubble-free product with good optical clarity. A typical flow sheet for the production of cast eet is shown in fig. lfi-40. Solution, suspension, and particularly emulsion polymerizations are also, widely used with the acrylics. Such polymerization reactions involve relatively conventional batch-type processes. i... 

In 1937 I.G.-Farbenindustrie patented a method for the preparation of polyaminoacetonitriles, corresponding acids and their derivatives . The process, known as the hydrogen cyanide process, utilizes sodium cyanide in acid solution. The cyanomethylation takes place by treatment of the amine with formaldehyde and hydrogen cyanide. In the case of ethylenediamine reaction (2) takes place ethylenediaminetetraacetonitrile (1) is isolated to ensure that the resulting tetrasodium salt, after hydrolysis, is not contaminated by by-products. This synthesis can be performed as a continuous process and is also used to obtain other complexones. The use of hydrogen cyanide and of an acid medium gives rise to corrosion and safety problems. 

The major part of these catalytic processes is carried out in fixed bed reactors. Some of the main fixed bed catalytic processes are listed in Table 11.1-1. Except for the catalytic cracking of gas oil, which is carried out in a fluidized bed to enable the continuous regeneration of the catalyst, the main solid catalyzed processes of today s chemical and petroleum refining industry appear in Table 11.1-1. However, there are also fluidized bed alternatives for phthalic anhydride— and ethylene dichloride synthesis. Furthermore, Table 11.1-1 is limited to fixed bed processes with only one fluid phase trickle bed process (e.g., encountered in the hydrodesulfurization of heavier petroleum fractions) are not included in the present discussion. Finally, important processes like ammonia oxidation for nitric acid production or hydrogen cyanide synthesis, in which the catalyst is used in the form of a few layers of gauze are also omitted from Table 11.1-1. 

A hydrolysis solution containing the neutral and cationic cyanoaquo-chromium(III) complexes can be prepared by combining potassium hexa-cyanochromate and perchloric acid in a molar ratio of 1 5. In a typical experiment, 0.65 g (2.00 mmoles) of potassium hexacyanochromate is dissolved in 250 ml of 0.04 M perchloric acid. The solution is kept in the dark at room temperature until the pH of the solution rises to 2.2, which takes approximately 40 to 45 hr. A stream of nitrogen is continuously bubbled through the solution to sweep out the liberated molecular hydrogen cyanide. 

---