75-13-8 cyanic acid

C2H4N2O3, NH2CONHCOOH. Unknown in the free state as it breaks down immediately to urea and COi- The NH4, Ba, Ca, K and Na salts are known and are prepared by treating ethyl allophanate with the appropriate hydroxide. The esters with alcohols and phenols are crystalline solids, sparingly soluble in water and alcohol. They are formed by passing cyanic acid into alcohols or a solution of an alcohol or phenol in benzene. The amide of allophanic acid is biuret. Alcohols are sometimes isolated and identified by means of their allophanates. 

In aqueous solution at 100° the change is reversible and equilibrium is reached when 95 per cent, of the ammonium cyanate has changed into urea. Urea is less soluble in water than is ammonium sulphate, hence if the solution is evaporated, urea commences to separate, the equilibrium is disturbed, more ammonium cyanate is converted into urea to maintain the equilibrium and evfflitually the change into urea becomes almost complete. The urea is isolated from the residue by extraction with boiling methyl or ethyl alcohol. The mechanism of the reaction which is generally accepted involves the dissociation of the ammonium cyanate into ammonia and cyanic acid, and the addition of ammonia to the latter ... 

Urea [57-13-6] was discovered ia urine by Rouelle ia 1773 and first synthesized from ammonia (qv) and cyanic acid by Woehler ia 1828. This was the first synthesis of an organic compound from an inorganic compound, and it dealt a deathblow to the vital-force theory. In 1870, urea was produced by heating ammonium carbamate ia a sealed tube. 

Cyanic acid (HOCN) reacts slowly, whereas undissociated HCN and HNO2 do not react at all (39). 

Ammonia reacts vigorously with phosgene. The products are urea, biuret, ammeUde (a polymer of urea), cyanuric acid, and sometimes cyameUde (a polymer of cyanic acid). The secondary products probably arise through the very reactive intermediate carbamyl chloride [463-72-9] NH2COCI (see... 

Benzoylene urea has been prepared by passing cyanogen into a solution of anthranilic acid in alcohol and hydrolyzing the resulting 2-ethoxy-4-ketodihydroquinazoline, by fusing anthranilic acid with urea, and by the action of aqueous cyanic acid on anthranilic acid. The procedure described is adapted from that of Bogert and Scatchard with several modifications. 

The first isocyanates were produced by Wurtz in 1849 by reacting organic sulphates with cyanic acid salts. 

Carbamyl and thiocarbamyl fluorides are obtained from hydrogen fluoride and cyanic acid or alkali metal cyanates or thiocyanates [/, 54] Nitnles give iraidofluoride salts with hydrogen fluoride [7] whereas hydrogen cyanide affords difluoromethylamine, which can be isolated as its hexafluoroarsinate salt [55) (equation II)... 

The hydroxyl derivative of X-CN is cyanic acid HO-CN it cannot be prepared pure due to rapid decomposition but it is probably present to the extent of about 3% when its tautomer, isocyanic acid (HNCO) is prepared from sodium cyanate and HCI. HNCO rapidly trimerizes to cyanuric acid (Fig. 8.25) from which it can be regenerated by pyrolysis. It is a fairly strong acid (Ka 1.2 x 10 at 0°) freezing at —86.8° and boiling at 23.5°C. Thermolysis of urea is an alternative route to HNCO and (HNCO)3 the reverse reaction, involving the isomerization of ammonium cyanate, is the clas.sic synthesis of urea by F. Wohler (1828) ... 

The reaction of diacetylene with cyanic acid (HCNO) proceeds at room temperature in the presence of sulfuric acid in aqueous methanol to give 3-formyl-5,5 -diisoxazol-3 -aldoxime (85) and 3,3 -diformyl-5,5 -diisoxazoldioxime (86), whose oxidation with potassium permanganate followed by esterification results in 3,3 -dicarbomethoxy-5,5 -diisoxazoles (87) (59G598). 

Cyan-saure, /. cyanic acid cyano acid, -schlamm, m. cyanide sludge, -senf l, n. cyanomustard oil. -silber, n. silver cyanide. -stickstoS, m. cyanonitride. -toluol, n. cyanotoluene. 

Ferrocyan-kaUum, n. potassium ferrocyanide. -kupfer, n. cupric ferrocyanide. -natrium, n. sodium ferrocyanide. -silber, n. silver ferrocyanide. -verbindung, /. ferrocyanide. -wasserstoff, m., -wasserstoffsMure, /. ferro-cyanic acid, -zink, n. zinc ferrocyanide. -zinn, n. tin ferrocyanide. 

The structures of these ylide polymers were determined and confirmed by IR and NMR spectra. These were the first stable sulfonium ylide polymers reported in the literature. They are very important for such industrial uses as ion-exchange resins, polymer supports, peptide synthesis, polymeric reagent, and polyelectrolytes. Also in 1977, Hass and Moreau [60] found that when poly(4-vinylpyridine) was quaternized with bromomalonamide, two polymeric quaternary salts resulted. These polyelectrolyte products were subjected to thermal decyana-tion at 7200°C to give isocyanic acid or its isomer, cyanic acid. The addition of base to the solution of polyelectro-lyte in water gave a yellow polymeric ylide. 

ISONITRILES. This designation includes isocyanides (see Vol 3, C582-L to C583-L and Vol 7, I135-R for Cyanicic Acid and-Derivatives) and Carbylamines, R.NiC. The first isonitriles were prepd in 1886 by Gautier, by the action of Ag cyanide on alkyl iodides. Later, Hofmann prepd them by the action of chlf ale KOH on primary amines ... 

When urea is heated alone or in aqueous solution it dearranges into ammonia and cyanic acid. The ammonia escapes, and if aniline is present the cyanic acid combines with it to form phenylmea. Phenyliurea dearranges in two modes which correspond to two methods for its formation. 

If it is heated alone at 160°, ammonia comes off rapidly, the aniline and phenylisocyanate may be detected by their odor but they combine in large part to form 5ym.-diphenyliu ea which crystallizes out from the hot liquid, and cyanic acid may be detected by means of silver nitrate in the water with which the apparatus is washed out after the experiment. When an aqueous solution of phenylurea is distilled, aniline may be detected in the distillate and 5ym.-diphenylurea crystallizes from the boiling liquid. By heating urea with the amine or with its hydrochloride at 160°, or by refluxing urea in aqueous solution with the amine or its hydrochloride, we have prepared sym.-6i-o- and />-tolyl, di-a- andjS-naphthyl, dimethyl, di-w-butyl, di-w- and i5 -amyl and dibenzylureas in satisfactory yield. 

If an aqueous solution of nitrourea is boiled, nitrous oxide escapes and the cyanic acid which is produced escapes in part, polymerizes in part, and in part remains in the aqueous liquid where it may react with various substances which may be introduced. If aniline is added to a saturated... 

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