Elimination hydrogen cyanide

Reaction of (58) with unsaturated nittile (59) produces 5-cyanopyrazoline (60), which on treatment with sodium ethoxide eliminates hydrogen cyanide to provide the pyrazole (61) in high yield (eq. 13). 

Azomethine ylides containing a leaving group can also be produced by the standard tautomerization route (e.g., species 60 with a cyano group on the ylide carbon). These species (e.g., 60 [R =Ph, PhCO,PhCH=CH R = H,Ph]) reacted with maleimides and with fiimarate, maleate, and acrylate esters to give adducts 61, which readily eliminated hydrogen cyanide (33). 

In 1821 Wohler discovered that a solid deposited from concentrated aqueous solutions of thiocyanic acid. The solid, which was called isoperthiocyanic acid (3-imino-5-mercapto-1,2,4-dithiazole) (361), formed a new product perthiocyanic acid (3,5-dimercapto-l,2,4-thiadiazole) (18) when treated with alkali and then acid. On storage perthiocyanic acid (18) readily reverted to isoperthiocyanic acid (361) (65AHC(5)119). The mechanisms of these interconversions are still not known with certainty but the transformations outlined in Scheme 130 are suggested. Wohler proposed the initial formation of a dimer of thiocyanic acid for which structure (359) appears resonable. Addition of the imine function of (359) to the nitrile function of HSCN would produce the trimer (360) which could readily eliminate hydrogen cyanide to produce isoperthiocyanic acid (361). 

A simple route to a cyanocarbene has been found by warming dimethylaminomalonitrile 116 to 60 °C under nitrogen, when it eliminates hydrogen cyanide and radicals are formed, as shown by the intense E.S.R. spectrum of the dimethylglycinonitrile radical, 117. The rather complex product mixture is consistent with formation of 117 elimination of HCN from 116 is a symmetry-allowed non-linear cheletropic fragmentation. 

Tertiary amines capable of eliminating a secondary amine to form a conjugated system can react with hydrogen cyanide to form y-keto nitriles by amine replacement. Thus (I) yields p-benzoylpropionitrile (IV) ... 

Mild acid converts it to the product and ethanol. With the higher temperatures required of the cyano compound [1003-52-7] (15), the intermediate cycloadduct is converted direcdy to the product by elimination of waste hydrogen cyanide. Often the reactions are mn with neat Hquid reagents having an excess of alkene as solvent. Polar solvents such as sulfolane and /V-m ethyl -pyrrol i don e are claimed to be superior for reactions of the ethoxy compound with butenediol (53). Organic acids, phenols, maleic acid derivatives, and inorganic bases are suggested as catalysts (51,52,54,59,61,62) (Fig. 6). 

Cyanohydrin Synthesis. Another synthetically useful enzyme that catalyzes carbon—carbon bond formation is oxynitnlase (EC 4.1.2.10). This enzyme catalyzes the addition of cyanides to various aldehydes that may come either in the form of hydrogen cyanide or acetone cyanohydrin (152—158) (Fig. 7). The reaction constitutes a convenient route for the preparation of a-hydroxy acids and P-amino alcohols. Acetone cyanohydrin [75-86-5] can also be used as the cyanide carrier, and is considered to be superior since it does not involve hazardous gaseous HCN and also virtually eliminates the spontaneous nonenzymatic reaction. (R)-oxynitrilase accepts aromatic (97a,b), straight- (97c,e), and branched-chain aUphatic aldehydes, converting them to (R)-cyanohydrins in very good yields and high enantiomeric purity (Table 10). 

An acrylonitrile plant eliminated 500,000 pounds of in-process storage of hydrogen cyanide by accepting a shutdown of the entire unit when the product purification area shut down. This forced the plant staff to solve the problems which caused the purification area shutdowns. 

Another acrylonitrile plant supplied by-product hydrogen cyanide to various other units. An inventory of 350,000 pounds of hydrogen cyanide was eliminated by having the other units draw directly from the acrylonitrile plant. This required considerable work to resolve many issues related to acrylonitrile purity and unit scheduling. 

A plant produced methyl methacrylate by reacting hydrogen cyanide with acetone to produce acetone cyanohydrin followed by further processing to produce methyl methacrylate. The hydrogen cyanide was produced at another site and was transported to the methyl methacrylate plant by railcar. A hydrogen cyanide plant was subsequently installed at the methyl methacrylate plant site to eliminate the need for shipping hydrogen cyanide or acetone cyanohydrin. 

Benzoin -As a small cjnantity of potassium cyanide is (apable of converting a large quantity of benzaldehyde into bciv/oin, the action of the cyanide has been explained as follows. The potassium cyanide first reacts with the aldehyde and forms a cyanhydnn, which then condenses with another molecule of aldehyde, hydrogen cyanide being finally eliminated (Lapwortbj,... 

The stereospecific generation of enamines by -elimination reactions (187) and a vinylogous elimination, which leads to a dienamine (188), have been reported. The loss of an a substituent from a tertiary amine is seen in the generation of enamines by elimination of hydrogen cyanide from benzylic a-aminonitriles (189,190). 

A convenient trap (Fig. 3) devised by John R. Johnson for the absorption of hydrogen chloride, or for the elimination of sulfur dioxide, hydrogen cyanide, etc., may be arranged as shown in the figure. The gases are led into a chamber in which a stream of water (from the reflux condenser in this case) flows downward into a large bottle. The bottle is provided with a... 

An approach to isobacteriochlorins1 ln-e makes use of Pd(II) or metal-free bilatrienes 1 as starting materials. Cyclization of the corresponding bilatriene derivatives is induced by base in the presence of palladium(II) or zinc(II) which exercise a template effect. Zinc can be readily removed from the cyclized macrotetracycles by acid whereas palladium forms very stable complexes which cannot be demetalated. Prior to the cyclization reaction, an enamine is formed by elimination of hydrogen cyanide from the 1-position. The nucleophilic enamine then attacks the electrophilic 19-position with loss of the leaving group present at the terminal pyrrole ring. 

In ethereal solution diazomethane can he preserved for a long time. Information about its numerous reactions (with hydrogen cyanide, acetylene, quinone, etc.) can he found in the special literature of the subject. As has already been mentioned, it is an important methylating agent, especially for phenols. With them it reacts in such a way that the two nitrogen atoms are eliminated as elementary nitrogen, and the two valencies which thus become free are occupied by H and OR. 

Acrylonitrile was made completely from acetylene in 1960 by reaction with hydrogen cyanide. For some years ethylene oxide was the raw material for addition of HCN and elimination of H2O. 

Both cyclic and acyclic ketoximes may be used in this transformation and the reaction is usually performed in an alcohol solution containing equimolar quantities of alkoxide. For a successful reaction, the starting material usually contains at least an a-methylene group but the presence of only one a-hydrogen may suffice. When treated with base the 0-acylated aldoximes do not react via the Neber rearrangement and instead they undergo an E2 elimination to cyanides or isocyanides. 

Cleavage is often associated with elimination of small, stable, neutral molecules, such as carbon monoxide, olefins, water, ammonia, hydrogen sulfide, hydrogen cyanide, mercaptans, ketene, or alcohols, often with rearrangement (Section 2.8). 

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