Hydrogen cyanid

It is readily oxidized by air to benzoic acid. With aqueous KOH gives benzyl alcohol and benzoic acid. Gives addition products with hydrogen cyanide and sodium hydrogen sulphite. 

CHjiCH-CN. Volatile liquid b.p. 78"C. Manufactured by the catalytic dehydration of ethylene cyanhydrin, by the addition of hydrogen cyanide to ethyne in the presence of CuCI or the reaction of propene, ammonia and air in the presence of a molybdenum-based catalyst. 

Legon A 0, Millen D J and Mjdberg P J 1977 The hydrogen cyanide dimer identification and structure from microwave spectroscopy Chem. Phys. Lett. 47 589... 

Dulmage W J and Lipscomb W N 1951 The crystal structures of hydrogen cyanide, HON Acta Crystallogr. 4 330... 

By (he direct addition of hydrogen cyanide to aldehydes and ketones, giving cyanhydrins ... 

C6H5CH(0H)CN I HCOCgHi - C6H5CH(OH)COC H, - HCN unchanged benzaldehyde, giving benzoin and regenerating the hydrogen cyanide... 

To 2 ml. of the ester, add 2--3 drops of a saturated freshly prepared solution of scdium bisulphite. On shaking, a gelatinous precipitate of the bisulphite addition product (D) of the keto form separates, and on standing for 5-10 minutes usually crystallises out. This is a normal reaction of a ketone (see p. 344) hydrogen cyanide adds on similarly to give a cyanhydrin. 

Hydrogen cyanide (inhaled) or alkali oanides (taken by mouth, rf. p. IQ2) inhale amyl nitrite from freshly opened capsules. Obtain medical attention urgently. 

If the reaction is allowed to become too vigorous, hydrogen cyanide is liberated and some glycolate is formed. 

By interaction of hydrogen cyanide and hydrogen chloride with an anxnatic compound (hydrocarbon, phenol or phenol ether) in the presence of aluminium chloride (or zinc chloride). This is known as the Gattermann... 

Mandelic acid. This preparation is an example of the synthesis of an a-hydroxy acid by the cyanohydrin method. To avoid the use of the very volatile and extremely poisonous hquid hydrogen cyanide, the cyanohydrin (mandelonitrile) is prepared by treatment of the so um bisulphite addition compound of benzaldehj de (not isolated) with sodium cyanide ... 

This operation should be conducted in a fume cupboard (hood) as hydrogen cyanide may be evolved. 

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) ... 

Cool the filtrate (A) to 5-10° and add concentrated hydrochloric acid dropwise and with vigorous stirring (FUME CUPBOARD hydrogen cyanide is evolved) to a pH of 1-2 (about 50 ml.) a crude, slightly pink 3-indoleacetic acid is precipitated. The yield of crude acid, m.p. 159-161°, is 20 g. Recrystallise from ethylene dichloride containing a small amount of ethanol 17 -5 g. of pure 3 indoleacetic acid, m.p. 167-168°, are obtained. 

Nitrogen and sulphur present. Just acidify 2-3 ml. of the fusion solution with dilute nitric acid, and evaporate to half the original volume in order to expel hydrogen cyanide and/or hydrogen sulphide which may be present. Dilute with an equal volume of water. If only one halogen is present, proceed as in tests (i) or (iii). If one or more halogens may be present, use tests (ii), (iii) or (iv). 

The conversion of primary alcohols and aldehydes into carboxylic acids is generally possible with all strong oxidants. Silver(II) oxide in THF/water is particularly useful as a neutral oxidant (E.J. Corey, 1968 A). The direct conversion of primary alcohols into carboxylic esters is achieved with MnOj in the presence of hydrogen cyanide and alcohols (E.J. Corey, 1968 A,D). The remarkably smooth oxidation of ethers to esters by ruthenium tetroxide has been employed quite often (D.G. Lee, 1973). Dibutyl ether affords butyl butanoate, and tetra-hydrofuran yields butyrolactone almost quantitatively. More complex educts also give acceptable yields (M.E. Wolff, 1963). 

The maximum yield of 2-alkylseIenazole is 25%. In this way. 4-methylselenazole (7) was obtained starting from hydrogen cyanide, hydrogen selenide and chloroacetone. It is the only known selenazole not substituted in the 2-position. The yield relative to chloroacetone is very low (2.5%) (Scheme 2). 

Lewis s concept of shared electron parr bonds allows for four electron double bonds and SIX electron triple bonds Carbon dioxide (CO2) has two carbon-oxygen double bonds and the octet rule is satisfied for both carbon and oxygen Similarly the most stable Lewis structure for hydrogen cyanide (HCN) has a carbon-nitrogen triple bond... 

With this as background let us now examine how the principles of nucleophilic addition apply to the characteristic reactions of aldehydes and ketones We 11 begin with the addition of hydrogen cyanide... 

The product of addition of hydrogen cyanide to an aldehyde or a ketone contains both a hydroxyl group and a cyano group bonded to the same carbon Compounds of this type are called cyanohydrins... 

The addition of hydrogen cyanide is catalyzed by cyanide ion but HCN is too weak an acid to provide enough C=N for the reaction to proceed at a reasonable rate Cyanohydrins are therefore normally prepared by adding an acid to a solution containing the carbonyl compound and sodium or potassium cyanide This procedure ensures that free cyanide ion is always present m amounts sufficient to increase the rate of the reaction... 

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