Hydrocyanic acid Synthesis

Several other methods are now employed industrially for the preparation of hydrocyanic acid. Synthesis from the elements is widely used. In this a mixture of hydrogen, carbon monoxide and nitrogen is passed through an electric arc, mixtures of nitrogen and hydrocarbons being sometimes employed, e.g., 20% methane, 10% hydrogen and 70% nitrogen. 

GattermaDD synthesis A method for the synthesis of aromatic hydroxyaldehydes. E.g. AICI3 is used to bring about the condensation of phenol with a mixture of gaseous hydrochloric acid and hydrocyanic acid an aldimine hydrochloride is formed and on hydrolysis gives p-hydroxybenzaldehyde... 

Miscellaneous Reactions. Sodium bisulfite adds to acetaldehyde to form a white crystalline addition compound, insoluble in ethyl alcohol and ether. This bisulfite addition compound is frequendy used to isolate and purify acetaldehyde, which may be regenerated with dilute acid. Hydrocyanic acid adds to acetaldehyde in the presence of an alkaU catalyst to form cyanohydrin the cyanohydrin may also be prepared from sodium cyanide and the bisulfite addition compound. Acrylonittile [107-13-1] (qv) can be made from acetaldehyde and hydrocyanic acid by heating the cyanohydrin that is formed to 600—700°C (77). Alanine [302-72-7] can be prepared by the reaction of an ammonium salt and an alkaU metal cyanide with acetaldehyde this is a general method for the preparation of a-amino acids called the Strecker amino acids synthesis. Grignard reagents add readily to acetaldehyde, the final product being a secondary alcohol. Thioacetaldehyde [2765-04-0] is formed by reaction of acetaldehyde with hydrogen sulfide thioacetaldehyde polymerizes readily to the trimer. 

The first methacrylic esters were prepared by dehydration of hydroxyisobutyric esters, prohibitively expensive starting points for commercial synthesis. In 1932 J. W. C. Crawford discovered a new route to the monomer using cheap and readily available chemicals—acetone, hydrocyanic acid, methanol and sulphuric acid— and it is his process which has been used, with minor modifications, throughout the world. Sheet poly(methyl methacrylate) became prominent during World War II for aircraft glazing, a use predicted by Hill in his early patents, and since then has found other applications in many fields. 

Hydrogen cyanide (hydrocyanic acid) is a colorless liquid (b.p. 25.6°C) that is miscible with water, producing a weakly acidic solution. It is a highly toxic compound, but a very useful chemical intermediate with high reactivity. It is used in the synthesis of acrylonitrile and adiponitrile, which are important monomers for plastic and synthetic fiber production. 

Recently, the enantioselective addition of hydrocyanic acid to aldehydes, analogous to the synthesis of (/ )-cyanohydrins, yielding (.S)-cyanohydrins in very high optical purity, with (S )-oxynitrilase as catalyst, was reported20,21. 

Further evidence for the formation of intermediate compounds in catalytic reactions is afforded by the observation (a) that optically active camphor is formed from optically inactive (racemic) camphor carboxylic acid in the presence of the d- or /-forms of quinine, quinidine or nicotine and (6) that optically active bases, e.g., quinidine, catalyze the synthesis of optically active mandelonitrile from benzaldehyde and hydrocyanic acid.10 These results hardly admit of any other interpretation than the intermittent production of a catalyst-reactant compound. 

Remarks on Sections 6 and 7.-—The method here described for the synthesis of cyanohydrins—treatment of the bisulphite compound of the aldehyde with potassium cyanide—cannot be used in all cases. Concentrated solutions of hydrocyanic acid or anhydrous hydrogen cyanide are often used. The general method for the synthesis of a-amino-acids, the nitriles of which are formed by the union of ammonium cyanide with aldehydes or ketones (Strecker), is to be contrasted with that for the synthesis of a-hydroxy acids. For additional amino-acid syntheses see Chap. VII. 2, p. 276. 

The industrial use of 1,3-dienes and of their electrophilic reactions has strongly stimulated the field in recent years. Because of the low cost of butadiene, abundantly available from the naphtha cracking process, very large scale applications in the synthesis of polymers, solvents and fine chemicals have been developed, leading to many basic raw materials of the modem chemical industry. For example, the primary steps in the syntheses of acrylonitrile and adiponitrile have been the electrophilic addition of hydrocyanic acid to butadiene24. Chlorination of butadiene was the basis of chloroprene synthesis25. 

Uses Fumigant and larvacide for tobacco, cereals, dried fruits cellulose acetate solvent military poison gases intermediate in manufacture of pharmaceuticals, hydrocyanic acid, N,N-dimethylformamide organic synthesis. 

When an aldehyde is allowed to react with an optically active amine and hydrocyanic acid, one of the two diastereomeric amino nitriles, (124a) or (124b), may be formed in excess. To prepare the chiral amino acids (125a) or (125b), the nitriles (124a) and (124b), respectively, are hydrolyzed with mineral acids, whereupon R is split off. However, this asymmetric synthesis of amino acids has no industrial significance. 

These molecules are flexible because rotation about single bonds is free, so they can wrap themselves around a metal ion to obtain four comfortable donor-atom-to-metal links within five-membered rings. Nitrilotriacetic acid is easily synthesized industrially from ammonia, formaldehyde, and hydrocyanic acid (the Strecker synthesis) and therefore is potentially an inexpensive but effective chelating agent. 

Hydrocyanic acid - [CYANIDES] (Vol 7) -atmospheric synthesis [IMINES, CYCLIC] (Vol 14)... 

FORMAMIDE. Form amide (meibanamide), HCONHi. is the lirsi member of the primary amide series and is the only one liquid at room temperature. II is hygroscopic and has a faint odor of ammonia. Formamide is a colorless to pale yellowish liquid, freely miscible with water, lower alcohols and glycols, and lower esters and acetone. It is virtually immiscible in almost all aliphatic and aromatic hydrocarbons, chlorinated hydrocarbons, and ethers. By virtue of its high dielectric constant, close to that of water and unusual for an organic compound, formamide has a high solvent capacity lor many heavy-metal salts and for salts of alkali and alkalinc-carth metals. It is an important solvent, in particular for resins and plasticizers. As a chemical intermediate, formamide is especially useful in the synthesis of heterocyclic compounds, pharmaceuticals, crop protection agents, pesticides, and for the manufacture of hydrocyanic acid. 

Initial preparative work with oxynitrilases in neutral aqueous solution [517, 518] was hampered by the fact that under these reaction conditions the enzymatic addition has to compete with a spontaneous chemical reaction which limits enantioselectivity. Major improvements in optical purity of cyanohydrins were achieved by conducting the addition under acidic conditions to suppress the uncatalyzed side reaction [519], or by switching to a water immiscible organic solvent as the reaction medium [520], preferably diisopropyl ether. For the latter case, the enzymes are readily immobilized by physical adsorption onto cellulose. A continuous process has been developed for chiral cyanohydrin synthesis using an enzyme membrane reactor [61]. Acetone cyanhydrin can replace the highly toxic hydrocyanic acid as the cyanide source [521], Inexpensive defatted almond meal has been found to be a convenient substitute for the purified (R)-oxynitrilase without sacrificing enantioselectivity [522-524], Similarly, lyophilized and powered Sorghum bicolor shoots have been successfully tested as an alternative source for the purified (S)-oxynitrilase [525],... 

Effenberger F, Eichhom J et al (1995) Enzyme catalyzed addition of hydrocyanic acid to substituted pivalaldehydes - a novel synthesis of (/J)-pantolactone. Tetrahedron Asymmetry 6 271-282... 

What a beautiful tool is cyanuric chloride for the chemist working in chemical synthesis Three chlorine atoms offer reaction with a large proportion of the chemicals listed in the Beilstein Handbook or the Chemical Abstracts Index. Not only that the chlorine atoms are reasonable enough not to react simultaneously but, under adequate conditions, stepwise, allowing myriads of potential combinations. Furthermore cyanuric chloride has been and is a relatively cheap key material it can be produced quite easily from such basic materials as chlorine and hydrocyanic acid. 

The third large-scale use of methane is in hydrocyanic acid production (1,2.3), and there are two known methods for HCN synthesis (Equations (7) and (S)) ... 

The preparation of cyanopyrazines by primary synthesis has been described in Section II.IH (286-288) and Section 11.2 (353-360). Further data have been recorded on the condensation of diaminomaleonitrile with glyoxal (1434, 1435), with a variety of 1,2-dicarbonyl compounds (1435, 1436), and Bredereck and Schmotzer (1044) have described the preparation from the tetramer of hydrocyanic acid with /J,p -dibromobenzil and p,p -diphenoxybenzil of 2,3-bis(p-bromo-phenyl)-5,6-dicyanopyrazine and 2,3-dicyano-5,6-bis(p-phenoxyphenyl)pyrazine, and with phosgene in dioxane of 2,3-dicyano-5,6-dihydropyrazine. Other preparations are described in Section II.3 (158, 383-387), with further data given in references 1050, 1154 and 1180, Section 11.5 (454) and Section 11.7 (484-486, 488-490). 

The two simple salts of hydrocyanic acid which are used in the synthesis of organic cyanogen compounds are potassium cyanide, K—(CN), and silver cyanide, Ag—(CN). These are both prepared by the action of the metallic oxides or hydroxides on the acid. 

S3mthesis from Cyanogen.—Two methods of synthesis of hydrocyanic acid support the view that this compound has the cyanide structure and not the iso-cyanide. Cyanogen gas because it yields oxalic acid on hydrolysis must have the constitution in which the two cyanogen groups are linked by the carbon atoms rather than nitrogen. 

From Acetylene.—The second synthesis of hydrocyanic acid supporting this same constitution is from acetylene by reaction with nitrogen under the influence of an electrical discharge. The nitrogen would split the acetylene molecule at the triple linkage of the two carbons leaving each hydrogen linked to carbon in the hydrocyanic acid. 

From Ammonia.—A third method for the synthesis of hydrocyanic acid supports the constitution of an iso-cyanide with the linkage of hydrogen to nitrogen. The Hofmann iso-nitrile reaction (p. 71) consists in the formation of iso-cyanides (iso-nitriles) by the reaction between chloroform and primary amines in the presence of an alkali. 

The synthesis of a-hydroxy acids from carbonyl compounds by way of the cyanohydrin was an early discovery in organic chemistry. In 1867 Simpson and Gautier, working in Wurtz laboratory, described the cyanohydrin from acetaldehyde and hydrocyanic acid, and its conversion to racemic lactic acid by strong hydrochloric acid. 

M. Simpson and A. Gautier, Compt. rend., 65, 414 (1867) J. Wislicenus had accomplished the synthesis from acetaldehyde, hydrocyanic acid and hydrochloric acid without isolating the cyanohydrin, Ann., 128, 22 (1863). 

The addition [44] of hydrocyanic acid to acetylene (eq. (20)) in a solution of copper chloride in aqueous hydrochloric acid gives good yields and, prior to the time when the synthesis of acrylonitrile by ammonoxidation [45] from propene became technically feasible, was the major preparation process. This synthesis, too, has nowadays completely lost its importance. 

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