Cyanuric acid salts

A 500-ml three-necked flask is fitted with a mechanical stirrer, a thermometer, a gas outlet, and a gas inlet tube dipping into the solution. The flask is charged with a solution of cyanuric acid (15 g, 0.116 mole) dissolved in 300 ml of 5% aqueous potassium hydroxide solution. The flask is cooled in an ice-salt bath with stirring to 0° and irradiated with a mercury lamp. A rapid stream of chlorine is passed into the flask (approx. 5 ml/sec), whereupon a heavy white precipitate forms. The addition of gas is continued until the solid material no longer forms (approx. 2 hours). The flask is briefly flushed with air, the product is collected by suction filtration in an ice-cooled funnel, and the residue washed with several small portions of cold water. Since it undergoes slow hydrolysis, the product should be dried in a vacuum oven. The crude product has a variable melting point (195-225°) the yield is about 20 g (approx. 75%). 

It also follows that protonation of the triazine ring makes it more susceptible to attack by nucleophilic reagents unless the reagent itself is also protonated. If the triazine ring remains unprotonated when a nucleophilic base, such as an alkylamine, is present as its acid salt the reaction is slower, of course. Cyanuric chloride itself is a very weak base that becomes protonated only under strongly acidic conditions. Thus step 1 in Scheme 11.2 can be carried out in aqueous solution even at pH 2 without risk of undesirable hydrolysis of cyanuric chloride, water being an extremely weak nucleophile. 

Above its melting point (360 0 about 90% of melamine cyanurate is converted to volatile products (360-450 0, 2nd step) in which free melamine and melamine cyanurate were recognised by IR. This indicates that a competition takes place between evaporation of the unalterated salt and its thermal dissociation to melamine and cyanuric acid. Melamine behaves then as described above while cyanuric acid which, heated alone in TG volatilises completely above 300 0, is known to decompose to cyanic acid (8). 

Its salts also exist in the form of a trimer, cyanuric acid (III), which is produced on heating the salts of isocyanic acid with acetic acid. Esters of cyanuric acid undergo isomerization when heated and are converted into esters of isocyanuric acid (IV) ... 

Cyanuric acid forms a variety of salts, most of which are not of major significance, but the trisilver salts are used to prepare tribromoisocyanurate and alkyl isocyanurates (Scheme 30) (67M1613). 

The thiocyanurates are readily hydrolyzed in acid to cyanuric acid and a thiol. Trimethyl trithiocyanurate reacts with sodium sulfide to give the trisodium salts. Melamine is formed on treatment of the thiocyanurates with aqueous ammonia at high temperatures the alkylthio groups are replaced sequentially <59HC(l3)l,p.lll), and can be removed using Raney nickel (equation 25) . 

Note Miscellaneous uses include cyanuric acid for chlorinated isocyanurates, crystalline adducts, deicing agents, pharmaceutical intermediates and sulfamic acid and its ammonium salt. 

SYNS ACL 70 CDB 60 DICHLOROCYANURIC ACID DICHLOROISOCYANUR. TE DICHLORO-ISOCYANURIC ACID DICHLOROISO-CYANURIC ACID, dry or dichloroisocyanuric acid salts (DOT) FI CLOR 71 HIUTE 60 ISOCYANURICACID.DICHLORO- ISOCYANURIC DICHLORIDE ORCED KYSELINA DICHLORISOKYAN UROVA (CZECH) TROCLOSENE... 

The cyanogen halides polymerize on standing to the trimers, the cyanuric halides. Cyanamide is converted into the corresponding trimer, melamine, on heating to about 150°C. Isocyanic acid, however, polymerizes far more readily. If urea is distilled, isocyanic acid is formed but polymerizes to cyanuric acid, (NCOH)3, a crystalline solid, the vapour of which, on rapid cooling, yields isocyanic acid as a liquid which, above 0 C, polymerizes explosively to cyamelide, a white porcelain-like solid. This latter material is converted into salts of cyanuric acid by boiling with alkalis. These reactions are summarized in Chart 21.1. Cyanuric derivatives... 

Cyanuric Acid. Organic cyanurates and isocyanurates have been prepared as pure materials and their use as metal precipitants has been reported in the literature (25-25). Diallylisocyanurate salts of cadmium, copper, and lead have been described and polyisocyanurates have been cited as precipitants for monovalent and divalent metal ions — including Cd, Hg and Pb —from waste streams (26). Initial tests with 10-34-0 (pH 6.8) indicated that ammonium cyanurate was soluble in the media however, no measurement of the solubility was made and no precipitate was observed. Addition of ammonium cyanurate to a 10-30-0 (pH 6.0) grade phosphate fluid fertilizer containing 40 ppm cadmium indicated low solubility of the reactant in the media and resulted in no cadmium removal at stoichiometries ranging from 25 to 480%. Confirmatory tests... 

Simple uncharged six-membered aromatic heterocycles cannot contain a divalent heteroatom. The azines are numbered to indicate the relative positions of the nitrogen atoms. 1,2,3,4-Tetrazine, pentazine and hexazine are unknown, however, a number of fused 1,2,3,4-tetrazines, primarily A -oxides and A -aryl quaternary salts, are known, but of monocycUc compounds, only a few di-A -oxides have been prepared. Of the other systems, 1,2,3,5-tetrazine is unknown, although theoretically it could be moderately stable, but fused derivatives include the drug temozolomide (see 33.7). Derivatives of 1,3,5-triazine are very well known and available in large quantities, indeed they are amongst the oldest known heterocycles the trioxy-compound ( cyanuric acid ) was first prepared in 1776 by Scheele by the pyrolysis of uric acid. 

Triazines are one of the oldest known compound classes in organic chemistry. First reports date back to 1776 when cyanuric acid (l,3,5-triazine-2,4,6-triol 1,3,5-triazine-2,4,6(l//,3//,5f/)-trione) was obtained by the pyrolysis of uric acid.1 The same method was also utilized in 1820 2 however, triazine compounds were probably first prepared in 1704 upon trimerization of cyanide derivatives when the Berlinerblau -complex salt, the first known cyano compound, was discovered.468 Cyanuric chloride was synthesized in 1828 from hydrogen cyanide and chlorine.3 Another method, discovered in 1834, involves treatment of potassium thiocyanate with chlorine. When heated, cyanuric chloride is obtained.4 Melamine (1,3,5-triazine-2,4,6-triamine) was also prepared in 1834 by heating potassium thiocyanate with ammonium chloride.5 Although 2,4,6-substituted 1,3,5-triazine derivatives were identified very early, the unsubstituted parent compound was not synthesized before 1895.6 At that time, however, the isolated compound was assigned to a dimeric species and not to the trimeric hydrogen cyanide. This was finally proven much later."... 

CHLORCYAN (506-77-4) CNCl C-N-CL Noncombustible gas. Violent polymerization can be caused by chlorine or moisture. Violent reaction with alcohols, alkenes, and alkynes (violent exothermic reaction) acids, acid salts, amines, strong alkalis, olefins, strong oxidizers. Contact with acid forms toxic hydrogen cyanide gas. Mixtures with benzene or cyanogen halides yield hydrogen chloride. In cmde form, this chemical trimerizes violently if catalyzed by traces of hydrogen chloride or ammonium chloride, forming cyanuric chloride. Alkaline conditions will convert this chemical to... 

CYANURE de ZINC (French) (557-21-1) Reacts with acids, acid fumes, acid salts, or elevated temperatures, releasing hydrogen cyanide gas. Can react violently with magnesium, nitrates. Incompatible with nitrites, chlorates. Mixtures of metal cyanides with metal chlorates, nitrates, nitrites, or perchlorates may cause violent explosions. Incompatible with strong oxidizers, bromine, chlorine, fluorine, mercurous chloride, nitric acid. Violent reaction with sodium nitrite. Forms sensitive explosive mixtures with potassium chlorate. 

Ammonia-type reductants, which include ammonia, urea, cyanuric acid and different ammonium salts, have been applied so far mainly for stationary sources. The apparent preference for a hydrocarbon reductant for a mobile deNOx system is mainly based on the following reasons (i) Hydrocarbons are always present in a combustion exhaust (ii) Equipping mobile sources witli an ammonia tank is considered unsafe (iii) Ammonia-type reductants require a stringent injection control to prevent ammonia slip (< 5 ppm required [12]) (iv) Ammonia is found to be converted to NO and N2O at liiglier temperatures (> 400 °C) over various SCR catalysts like V2O5 [12 - 14], WO3 [13] and CrjOs [15] (v) SO2 present in a combustion exhaust is often converted to SO3 to produce acidic particulates [13]. 

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