Iso cyanic acid

Since there is only one cyanic acid, we do not consider it correct to drop this name and, as is often done, to call the substance iso-cyanic acid. 

Fulminates are salts of fulminic or para-cyanic acid (qv), which is isomeric with iso-cyanic acid. Fulminates should not be con-fu sed with Fulminating Compounds (qv). Struc rural formulas of fulmiriic.acid and of its salts... 

Fulminates are salts of fulminic or para-cyanic acid (qv), which is isomeric with iso-cyanic acid. Fulminates should not be confused with Fulminating Compounds (qv). Structural formulas of fulminic acid and of its salts have not yet been definitely established. The free fulminic acid has not been isolated from its solns, as it undergoes polymerization very rapidly both in aqueous and in ethereal solns. The acid and its metallic salts, M(ON C)n, are very poisonous and explosive. The best known and most used salt is Mercuric Fulminate (qv)... 

C. CYANIC ACID, ISO-CYANIC ACID, THIO-CYANIC ACID AND THEIR SALTS... 

Iso-cyanic Acid.—If hydrocyanic acid is analogous to hydrochloric acid we should expect an oxygen acid to be obtained from it analogous to hypochlorous acid. 

An acid of this composition is known but it has been shown to have another constitution, viz., H—N=C = O, and is iso-cyanic acid though it is often called cyanic acid. It is an odorous, unstable liquid. We have already discussed (p. 73) the alkyl derivatives of these two acids. 

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. 

Potassium Cyanate.—When iso-cyanic acid is neutralized with potassium hydroxide, potassium cyanate is obtained. Potassium cyanate is also obtained when potassitun cyanide is oxidized by means of lead oxide or potassium bichromate. 

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. 

Such a rearrangement when iso-cyanic acid is neutralized and converted into salts of cyanic acid is an interesting phenomenon. 

Cyanuric Acid.—That iso-cyanic acid has the constitution given to it is established by the constitution of the alkyl derivatives which are not true esters (p. 73) and also by its relation to cyanuric acid. This latter acid is a polymer of iso-cyanic acid, viz., (HNCO)3. It is obtained by heating urea and the reactions will be considered presently when we study this compound. This source of the acid is the basis of the name cyan-uric acid. It is a solid crystallizing from water solution in prisms which contain two molecules of water of crystallization. Like iso-cyanic acid cyanuric acid yields alkyl derivatives of two isomeric forms, corresponding to polymers of cyanic and iso-cyanic acid derivatives. The ethyl derivatives have the following constitutions ... 

Fulminic Acid.—Detonating taps used for exploding the charges of gun cartridges, shells and dynamite cartridges are made of mercury fulminate, a salt of fulminic acid. This acid has the same composition as cyanic acid and iso-cyanic acid. The constitution is, however, different from either and is that of a normal iso-cyanic acid in which the hydrogen is linked as hydroxyly to the nitrogen and not directly as in iso-cyanic acid. 

Corresponding to the cyanic and iso-cyanic acids and their salts and esters, we have the analogous sulphur or thio compounds formed by the replacement of oxygen by sulphur. The relationship of these sulphur compounds to the oxygen compounds is exactly the same as that existing between sulphuric acid and thio-sulphuric acid. 

Iso-thio-cyanates.—Isomeric with the thio-cyanic acid would be iso-thio-cyanic acid which if analogous in constitution to the iso-cyanic acid should have the constitution H—N = C = S. Neither this compound nor metal salts of it are known but alkyl derivatives are known as constituents of oil of mustard (p. 165). 

Also when urea loses one molecule of ammonia from one molecule of urea by the action of phosphorus pentoxide we obtain cyanuric acid and iso-cyanic acid (p. 418). 

A somewhat different type of alkylating agent is the N-alkyl- -nitrosourea. Compounds of this cla.ss are unstable in aqueous solution under physiological conditions. They produce carbonium ions (also called carhen mm ions) that can alkylate and isocyanates that can carbamoylate. For example. melhylnitrosourea decompo.scs initially to form iso-cyanic acid and mcthyldiazohydroxide. The latter species decomposes further to methyidiazonium ion and finally to methyl carbonium ion. the ultimate alkylating species. ... 

A possible practical way to eliminate oxides of nitrogen (such as NO2) from automobile exhaust gases uses cyanuric acid, C3N3(0H)3. When heated to the relatively low temperature of 625°F, cyanuric acid converts to gaseous iso-cyanic acid (HNCO). Isocyanic acid reacts with NO2 in the exhaust to form nitrogen, carbon dioxide, and wateg all of which are normal constituents of the air. 

Isocyanates can also be made by reaction of salts of iso-cyanic acid with alkyl halides (2.23).60 A disadvantage is that this produces by-product salt. 

Organic isocyanates are compounds containing the isocyanate group —N=C=0 attached to an organic group. They are esters of iso-cyanic acid HNCO. They form polymers, commonly called polyurethanes, which are of great commercial application. 

H2N-CO-NH2 (melt) + heat- NH4NCO(melt) NH3(g) + HNCO(g) urea ammonium iso-cyanate ammonia iso-cyanic acid... 

In practice, therefore, diamines alone are converted with urea in the melt or in solution (e.g., phenol). The reaction possibly proceeds via iso-cyanic acid (from the urea). On heating to 140-160°C, ammonia is vigorously evolved. The prepolymer thus formed is then condensed out under vacuum at 250°C. Since the end groups are labile groups, (— NH—CO—NH2, —NCO ), they are stabilized by the addition of regulators (monobasic acids, amides, amines). The formation reaction is an equilibrium reaction transureidation is thus possible. 

Any processes that can lead to the formation or disappearance of phase-separated or homogeneously mixed binary SAMs can be monitored through the change in the desorption peak in voltammo-grams. Figme 16 shows an example of detecting the rate of a surface chemical reaction using the shift in Ep. When iso-cyanic acid n-butyl ester in toluene reacted... 

Ethyl carbamate in wine is formed (mostly at the end of fermentation) from urea. The intermediates of its degradation are probably cyanates and cyanic acid (HO-C=N), also known as hydrogen cyanate, which may isomerise to isocyanic acid (H-N=C=0). Iso-cyanic acid can also arise by protonation of the cyanate anion and nucleophilic addition of ethanol to isocyanic acid yields ethyl carbamate. Isocyanic acid also reacts with other nucleophilic reagents, such as water (with formation of ammonia and carbon dioxide), thiols and amino groups of proteins. By catalysis with ornithinecar-bamoyl transferase, citrulline is transformed into ornithine and carbamoyl phosphate, the ethanolysis of which yields ethyl carbamate (Figure 12.39). 

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