Potassium cyanate

The crude potassium cyanate is satisfactory for many purposes. However, an aqueous solution of this product should be filtered before use. The crude product may be purified by a careful recrystallization. Caution. It mmt he rememhei ed that potassium cyanate in aqueous solution hydrolyzes slowly, even at room temperature, forming ammonium and carbonate ions. If the temperature limit is exceeded or the work is not carried ovi promptly, the recrystallized product may he less pure than the starting material. 

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Ammonium cyanate, because of its instability in solution, is usually prepared (NHJaSO, + 2KCNO 2NH4CNO + KjSO by mixing aqueous solutions of ammonium sulphate and potassium cyanate. Complete evaporation then gives a mixture of potassium sulphate and urea, from which the urea may be extracted w ith hot absolute ethanol, in which potassium sulphate is insoluble. 

When the potassium cyanate used in the above preparation is replaced by potassium thiocyanate (or sulphocyanide), the ammonium thiocyanate formed undergoes partial rearrangement to thiourea (or sulpho-urea). Even above... 

Mono-substituted and unsymmetrical di-substituted ureas may be prepared by a modification of Wohler s urea synthesis, salts of primary or secondary amines being used instead of the ammonium salt for interaction with potassium cyanate. Thus when an aqueous solution containing both aniline hydrochloride and potassium cyanate is heated, aniline cyanate is first formed, and then C,HjNH,HCl -h KCNO = C,H6NHj,HCNO -h KCl C,HsNH HCNO = C.H NHCONH, by the usual molecular rearrangement is converted into monophenyburea. 

Dissolve 5 g. of aniline hydrochloride in 120 ml. of hot water contained in a 200 ml. conical flask and then add 4 g. of potassium cyanate. Heat the solution on a water-bath for 30 minutes, adding about 1-2 g. of animal charcoal towards the end of the heating if a slight turbidity has developed. Now bring the solution quickly to the boil over a gauze, and filter it at the pump, using a Buchner funnel and flask which have been preheated by the filtration of some boiling distilled water. The clear... 

Chemical Properties. Potassium cyanide is readily oxidized to potassium cyanate [590-28-3] by heating in the presence of oxygen or easily reduced oxides, such as those of lead or tin or manganese dioxide, and in aqueous solution by reaction with hypochlorites or hydrogen peroxide. 

Potassium cyanate [590-28-3] M 81.1, d 2.05, pK 3.46 (for HCNO). Common impurities include ammonia and bicarbonate ion (from hydrolysis). Purified by preparing a saturated aqueous solution at... 

The yield is highly dependent upon the quality of the potassium cyanate employed, and some samples were found worthless for the purpose. The yields given were realized using Eastman s regular grade of potassium cyanate. 

The improved method herein described is adapted from the procedure of Runti and Deghenghi. Hydroxyurea has been prepared from potassium cyanate and hydroxylamine hydrochloride. A lower melting isomeric substance, m.p. 71°, has been described." " The structure NH2CO2NH2 has been proposed for this low-melting substance. 

Silver cyanate should be freshly prepared. The commercial material has a pronounced gray color and is totally unsuitable for this reaction. Best results are obtained when the following preparation is carried out in the dark. To 100 g of silver nitrate in 3 liters of distilled water is added with stirring 49.5 g of potassium cyanate in 700 ml of distilled water. The white precipitate is filtered through a large Buchner funnel (Coors No. 5) and the filter cake is washed with 500 ml water, then with 300 ml methanol, and finally with... 

Uramil and potassium cyanate unite to form potassium pseudo-urate,... 

Undoubtedly these reactions proceed via an intermediate ureido or thioureido derivative. These compounds have been obtained by Dornow and Hahmann by the action of potassium cyanate or ammonium isothiocyanate on 2-amino-4,6-dimethylnicotinic acid (11), but whereas the urea (12, X = 0) was converted into the pyrido[2,3-li]-pyrimidine-2,4(lI/,3/7)-dione (13, X = 0) by the action of heat, the thiourea (12, X = S) was unchanged after similar treatment. 

The 6-methyl derivative (98, R = Me) was an important intermediate in the synthesis of analogs (e.g., 183) of folic acid. Korte has shown that 2-aminopyrido[3,2-guanidine carbonate with 3-aminopicolinic acid and that treatment of the same acid with ammonium thiocyanate or potassium cyanate yields the thioureido and ureido derivatives (100, X = S and X = 0). In contrast to the pyrido[2,3-d]pyrimidine system bsoth of these compounds could be cyclized by heat and the latter (100, X = O) is a likely intermediate in the synthesis of the dione (98) by the fusion with urea. 

Gabriel and Lauer first prepared a 2-iminotetrahydro-l,3-oxazine (28a) as early as 1890 by reacting y-bromopropylamine hydrobromide and potassium cyanate ... 

Fluproquazone (97) contains a 2-quinazolinone nucleus and is found to be an analgetic agent useful in mild to moderate pain. One of the preparations involves reaetion of 2-isopropylamino-4-methyl-4 -fluoro-benzophenone (96) with potassium cyanate in hot acetic acid [27],... 

Urea maybe reacted with acetoacetic ester and that product nitrated to give 5-nitro-orotec acid That is hydrogenated, then reacted with urea and potassium cyanate to give tetrahydroxypy-imidopyrimidine. The tetrahydroxy compound Is converted to the tetrachloro compound POCI3. Reaction with diethanolamine and then with piperidine gives dipyridamole. 

Azepines are much less common than the 1H- and 3//-isomers, and one of the few general synthetic approaches to this system is by base-catalyzed ring expansion of 4-(chloromethyl)-l, 4-dihydropyridines. e. g. I.29 Curiously, the ring expansion is also effected by potassium cyanate in refluxing ethanol. 

Hydantoin can be prepared in a variety of ways, notably from glycine2 or ethyl aminoacetate8 and potassium cyanate. The checkers used Eastman Kodak white label hydantoin. 

Acetylation of the hydroxymethyl imidazole 63 affords the corresponding ester (64), nitration (65) followed by hydrolysis gives intermediate 66, and reaction of this alcohol with potassium cyanate in hydrogen fluoride gives the carbamate ronidazole (67).16... 

Potassium 4-chloro-3,5-dinitrobenzene-sulfonate, 31, 46 Potassium cyanate, 31, 9 Potassium cyanide, 30, 84 32, 31, 63 Potassium ethyl xanthate, 30, 56 Potassium hydroxide, 30, 103 Potassium iodide, 30, 34 31, 31, 66 Potassium methyl sulfate, 31, 73... 

A precipitate, explosive when touched after drying, which appeared from a neutralised solution stood overnight with a large excess of potassium cyanate, was described as a fulminate. This is unlikely, though fulminating gold is probable, cyanate hydrolysing to release ammonia (see above). Existence of explosive cyanate complexes is also conceivable. 

Early studies on 4(5)-aminoimidazole (25 R=H) gave a stable urea derivative (37BJ488). Thus, treatment of a solution of 4(5)-aminoimidazole (25 R = H), made slightly acidic by addition of acetic acid, with potassium cyanate gave AMmidazol-4-yl-urea (31) (8%). TV-Imidazol-4-yl-urea (31) was similarly obtained using the dihydrochloride salt of 4(5)-aminoimidazole (25 R = H) (41MI1). 

WILLIAMS, D. L., and A. R. Ronzio Preparation of Potassium Cyanate from... 

Recently, the solvolyses of l-chloro-l,3,3-triarylallenes 10 (andof 1-butyl-3,3-diphenyl-allenyl chloride) were carried out in the presence of thiocyanate and o-ethyl dithiocar-bonate anions as nucleophiles and found to give the corresponding allenyl derivatives 11 and 12 in good yield (equation 3)18. However, when potassium cyanate was used as a nucleophile, the cyanate ion attacked at the /-position to give the propargyl amines 14 after decarboxylation of the unstable intermediate 13 (equation 4). 

Potassium 4-chloro-3,5-dinitrobenzene-sulfonate, 31, 46 Potassium cyanate, 31, 9 Potassium cyanide, 30,84 32,31,63 37,47 Potassium ethyl malonate, 37, 34 Potassium ethyl xanthate, 30, 56 Potassium fluoride, 36, 40 Potassium iodide, 30, 34 31, 31, 66 Potassium metal, 37, 29, 30 Potassium methyl sulfate, 31, 73 Potassium nitrate, 31, 46 Potassium 1-nitropropylnitronate, 37, 24 Potassium oxalate, 34, 83 Potassium permanganate, 30, 87 31, 59 Potassium sulfide, 32, 103 Potassium thiobenzoate, 32, 101 Potassium thiocyanate, 32, 39, 40 Prins reaction, 33, 72 Propane, 1, 3-dibromo-2, 2-Ws-(bromo-methyl)-, 31, 82... 

The first reported synthesis of hydroxyurea (24) consists of the condensation of hy-droxylamine with potassium cyanate (Scheme 7.14) [87]. Condensation of hydroxy-lamine with ethyl carbamate also gives pure hydroxyurea in good yield after recrystallization (Scheme 7.14) [88]. Nitrogen-15 labeled hydroxyurea provides a useful tool for studying the NO-producing reactions of hydroxyurea and can be prepared by the condensation of N-15 labeled hydroxylamine with either potassium cyanate or trimethylsilyl isocyanate followed by silyl group removal (Scheme 7.14) [89, 90]. Addition of hydroxylamine to alkyl or aryl isocyanates yields alkyl or aryl N-hydroxyureas (Scheme 7.14) [91, 92]. The condensation of amines with aromatic N-hydroxy carbamates also produces N-substituted N-hydroxyureas (Scheme 7.14) [93]. 

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