Cyanic acid, potassium salt

CYANHYDRINE d ACETONE (FRENCH) see MLC750 CYANIC ACID, POTASSIUM SALT see PLC250 CYANIC ACID, SODIUM SALT see COI250 CYANIC ACID, TRIMETHYLSTANNYL ESTER see TMIlOO... 

Cyanamide, calcium salt Cyanamide, dimethyl-Cyanic acid, potassium salt Cyanide ion Cyanide radical... 

Cyanex 921. See Trioctylphosphine oxide Cyanic acid, potassium salt. See Potassium cyanate... 

CAS 590-28-3 EINECS/ELINCS 209-677-9 Synonyms Cyanic acid, potassium salt Potassium isocyanate... 

Of the various published methods of preparing phenylurea, such as treatment of aniline salts with potassium cyanate in water solution,1 heating aniline with urea,2 with cyanic acid,3 or with cyanogen chloride,4 and the interaction of phenyl isocyanate or phenylcarbamine chloride with ammonia,5 the only ones to be considered as practical methods for preparation are the first two. The first suffers from the disadvantage that potassium cyanate is not easily prepared in the laboratory and rapidly undergoes spontaneous decomposition in storage while by the action of urea on aniline alone, carbanilide is formed in rather larger proportion than phenylurea. 

Cobalti-cyanic Acid,Hydrogen Cobalti-cyanide, H3Co(CN)6.H20.— The free acid may be prepared by decomposing a concentrated aqueous solution of the potassium salt with sulphuric acid, a slight excess of the latter being added. The mixture is warmed, and upon addition of alcohol potassium sulphate separates out, the hydrogen cobalti-cyanide... 

This same substitution of sulphur for oxygen occurs in the case of cyanic acid and its salts, e.g., potassium thio-cyanate and ammonium thiocyanate used as reagents in testing for ferric iron. 

Thus while isomeric derivatives are known corresponding to two isomeric acids only one acid is known and this one has the structure of the iso-cyanic acid. When we study the salts obtained from this iso-cyanic acid we find, unlike the alkyl derivatives, that they are known in only one form but strangely enough in the form of the cyanic acid, e.g, K—O—C=N, potassium cyanate. 

Ammonium Cyanate.— The corresponding ammonium salt, viz., ammonium cyanate, NH4OCN, may be easily prepared from the potassium cyanate by treating a solution of the latter with the calculated amount of ammonium sulphate. This compound is of especial interest because on evaporation of the water solution to dryness a rearrangement takes place and urea is formed (p. 429). Ammonium cyanate is also formed when iso-cyanic acid is neutralized with ammonia. 

Most alkaloids are isolated from plant extracts by conversion into the difficultly soluble salts which they form with complex acids such as hexachloroplatinic acid, chlorauric add, phosphotungstic add, hydroferro-cyanic add, Rdnecke s add, etc. Perchloric add, picric add, flavianic add, mercuric chloride, iodine in potassium iodide are also used. 

The earliest method of this type was the old Marckwald synthesis (1] in which a suitable a-aminocarbonyl compound is cyclized with cyanate, thiocyanate or isothiocyanatc. More recent modifications have employed the acetals of the a-amino aldehyde or ketone or an a-amino acid ester. The two-carbon fragment can also be provided by cyanamide, a thioxamate, a carbodiimidc or an imidic ester. When cyanates, thiocyanates or isothiocyanates are used, the imidazolin-2-ones or -2-thiones (1) are formed initially, but they can be converted into 2-unsubstituted imidazoles quite readily by oxidative or dehydrogenative means (Scheme 4.1.1). The chief limitations of the method arc the difficulty of making some a-aminocarbonyls and the very limited range of 2 substituents which are possible in the eventual imidazole products. The method is nonetheless valuable and widely used, and typically condenses the hydrochloride of an a-amino aldehyde or ketone (or the acetals or ketals), or an a-amino-)6-ketoester with the salt of a cyanic or thiocyanic acid. Usually the aminocarbonyl hydrochloride is warmed in aqueous solution with one equivalent of sodium or potassium cyanate or thiocyanate. An alkyl or aryl isocyanate or isothiocyanate will give an A-substituted imidazole product (2), as will a substituted aminocarbonyl compound (Scheme 4.1.1) [2-4]. 

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