Cyanamides ureas

Prussic Acid Methyl Cyanide Cyanic Acid Urea Cyanamid... 

Supplement (combined with Volume IV) III, 2nd 1929 195-449 Hydroxy-carboxylic acids Carbonic acid, 3. GlycoUic acid, 228. Lactic acid, 261. Tartaric acid, 481. Citric acid, 556. Urea, 42. Cyanamide, 74. Thiocyemic acid, 140. 

Urea is also used as feed supplement for mminants, where it assists in the utilization of protein. Urea is one of the raw materials for urea—formaldehyde resins. Urea (with ammonia) pyrolyzes at high temperature and pressure to form melamine plastics (see also Cyanamides). Urea is used in the preparation of lysine, an amino acid widely used in poultry feed (see Amino acids Feeds and feed additives, petfoods). It also is used in some pesticides. 

JMethylphosphonc Acid—Cyanamide System. In another system (65), based on methylphosphoric acid [993-13-5] (MPA) and cyanamide [420-04-2] one or more of the hydroxyls in MPA or in its dimer react with cellulose and the water is taken up by the cyanamide, forming urea ... 

The identification of Tris as a potential carcinogen dealt a resounding blow to the flame-retardant finishing industry. From 1977 to 1984, several principal supphers of flame-retardant chemicals either reduced the size of their operations or abandoned the market completely. However, Albright and Wilson Corp. (UK) continues to produce THPC—urea precondensate and market it worldwide, and Westex Corp. (Chicago) continues to apply precondensate—NH finish to millions of yards of goods for various end uses. American Cyanamid reentered the market with a precondensate-type flame retardant based on THPS. 

Melamine. Melamine (cyanurotriamide, 2,4,6-ttiainino-j -triazine) C H N, is a white crystalline soHd, melting at approximately 350°C with vaporization, only slightly soluble in water. The commercial product, recrystallized grade, is at least 99% pure. Melamine was synthesized eady in the development of organic chemistry, but it remained of theoretical interest until it was found to be a usehil constituent of amino resins. Melamine was first made commercially from dicyandiamide [461-58-5] (see Cyanamides), but is now made from urea, a much cheaper starting material (9—12) (see also... 

Urea is dehydrated to cyanamide which trimerizes to melamine in an atmosphere of ammonia to suppress the formation of deamination products. The ammonium carbamate [1111-78-0] also formed is recycled and converted to urea. For this reason the manufacture of melamine is usually integrated with much larger facilities making ammonia and urea. 

Ammonia is used in the fibers and plastic industry as the source of nitrogen for the production of caprolactam, the monomer for nylon 6. Oxidation of propylene with ammonia gives acrylonitrile (qv), used for the manufacture of acryHc fibers, resins, and elastomers. Hexamethylenetetramine (HMTA), produced from ammonia and formaldehyde, is used in the manufacture of phenoHc thermosetting resins (see Phenolic resins). Toluene 2,4-cHisocyanate (TDI), employed in the production of polyurethane foam, indirectly consumes ammonia because nitric acid is a raw material in the TDI manufacturing process (see Amines Isocyanates). Urea, which is produced from ammonia, is used in the manufacture of urea—formaldehyde synthetic resins (see Amino resins). Melamine is produced by polymerization of dicyanodiamine and high pressure, high temperature pyrolysis of urea, both in the presence of ammonia (see Cyanamides). 

Carbamic acid is the monoamide of carbonic acid the diamide is the weU-known compound urea [57-13-6] also called carbamide (see Urea). Guanidine [113-00-8] could be regarded as the amidine of carbamic acid (see Cyanamides). 

For production of commercial 50% solution and for recovery of crystalline cyanamide, this process is modified to improve purity and concentration. Calcium and iron may be removed by ion-exchange treatment. The commercial 50% solution is stabilized at pH 4.5—5.0 with 2% monosodium phosphate and contains less than 1.5% dicyandiamide and 0.2% urea. Such solutions are expected to show less than 1% change ia cyanamide content per month of storage below 10°C. It is advisable, however, to adjust the pH periodically duriag extended storage. Organic esters may be used iastead for improved stabihty (23). 

Reaction of lime and urea forms calcium cyanate [6860-10-2] (26) which is then converted to calcium cyanurate [32665-90-0], the latter gives calcium cyanamide at a higher temperature ... 

Specifications and Analysis. Cyanamide is sold as anhydrous, aqueous 50%, and calcium cyanamide. Aqueous 50% cyanamide solutions contain a buffer additive, usually 2% NaH2P04, to stabilize the pH and prevent formation of dicyandiamide and urea. Calcium cyanamide is stable under dry conditions. Table 2 gives a typical analysis of the three commercial forms. 

Handling and Storage. Cyanamide solution dimerizes to dicyandiamide and urea with the evolution of heat and a gradual increase in alkalinity accelerating the reaction. Storage above 30°C without pH stabilizer leads to excessive dimerization and can result in violent exothermic polymerization. Cyanamide should be stored under refrigeration and the pH tested periodically. Stabilized cyanamide can be kept at ambient temperature for a few weeks. 

Reactions. The reactions of dicyandiamide resemble those of cyanamide. However, cycUzations take place easily and the nitrile group is less reactive. Under pressure and ia the presence of ammonia, dicyandiamide cyclizes to melamine. Considerable toimages of melamine have been made ia this manner however, melamine is produced chiefly by the urea process (43). 

Urea has been obtained from calcium cyanamide via cyanamide ... 

I-Cyano-3-phenylurea, first obtained by the alkaline hydrolysis of 5-anilino-3- -toluyl-l,2,4-oxadiazole, has been prepared by tlic condensation of phenyl isocyanate and the sodium salt of cyanamide. However, in these publications an incorrect structural assignment for the product was made. 1-Cyano-3-phenyl-urea is obtained also, together with other products, by warming gently l-cyano-3-phenylthiourea with caustic soda in the presence of ethylene chlorohydrin, or by gradually adding caustic )otash to a boiling solution of 1-phenyldithiobiuret and ethylene clilorohydrin in ethanol. ... 

Sodium borohydride reduction of 4-substituted isoquinolinium salts led to vinylogous cyanamides, ureas, and urethanes, as well as the corresponding tetrahydroquinolines (640). Hydrogenation of /8-acylpyridinium salts (641) to vinylogous ureas was exploited in syntheses of alkaloids (642), leading, for instance, to lupinine, epilupinine, and corynantheidine (643, 644). Similarly, syntheses of dasycarpidone and epidasycarpidone were achieved (645) through isomerization of an a,/0-unsaturated 2-acylindole and cyclization of the resultant enamine. 

Amino resins are condensation thermosetting polymers of formaldehyde with either urea or melamine. Melamine is a condensation product of three urea molecules. It is also prepared from cyanamide at high pressures and temperatures ... 

The Ritter reaction can be applied to cyanamides RNHCN to give ureas (RNHCONHR ). ... 

Guanidine dearranges less readily than urea and yidds ammonia and cyanamide as would be expected from the familiar method for its synthesis. If it is heated with aniline, the cyanamide shows no tendency to combine with that substance but combines with itself, as it does in the absence of aniline, to form melamine. 

The constituent of paint, 2-nitropropane, exhibiting genotoxicity and hepatocarcinogeni-city was oxidized by liver microsomes forming nitric oxide, which was identified as a ferrous NO complex [61]. Clement et al. [62] concluded that superoxide may participate in the microsomal oxidation of /Y-hydroxyguanidincs, which produced nitric oxide, urea, and the cyanamide derivative. Caro et al. [63] suggested that the oxidation of ketoxime acetoxime to nitric oxide by microsomes enriched with P-450 isoforms might be mediated by hydroxyl or hydroxyl-like radicals. 

Marcotrigiano et al.39 suggested that the desulfuration of thiourea in sodium hydroxide results in the formation of cyanamide, amidinourea, and guanidine at a pH below 12 they also suggested that the formed urea converts to ammonium cyanate and finally to ammonium carbonate (by hydrolysis). The pro-... 

An alternative mechanism [8] entails reaction of cyanamide (or dicyandiamide) with the dye phosphonate to give an O-acylisourea derivative (7.47). This is able to react directly with cellulose to form dye-fibre bonds, urea being released as the anticipated by-product (Scheme 7.31). In support of this mechanism, it is known that O-acylisourea derivatives of arylcarboxylic acids react readily with alcohols and this constitutes an efficient route for the preparation of carboxylic esters [44]. 

Polyethylene was discovered by ICI in 1933 while polytetrafluoroethylene was discovered by Plunnekett. Urea-formaldehyde resins which were made in 1920 were used for moulding. Melamine formaldehyde resins were introduced by American Cyanamid Company in 1939. 

Another of the early thermo-setting resins was the urea formaldehyde resin developed by American Cyanamid. Urea and formaldehyde gave methylol and dimethylol urea which on heating, further condensed to give the colorless resin. The technology of this process was well worked out, but the chemistry was still not completely understood. The colorless resin has been used to make many varieties of decorative materials and some essentially unbreakable dishes, among other uses. 

Amides [41,44], thioamides [41 ] and amidines [45] are converted into nitriles by the reaction with dichlorocarbenes generated by Makosza s procedure (Table 7.16). Under similar conditions, monosubstituted and A.A-disubstituted ureas are converted into cyanamides (Table 7.17) JV,(V -disubstituted ureas produce carbodi-imides in low yield [41,46,47]. /V-Carbamoyl derivatives of dibenzo[/ /]diazepines and the related 10, l l-oxirane derivatives are converted into the corresponding... 

Selected examples of the conversion of IVA-disubstituted ureas into cyanamides... 

The synthesis of the oligomers involved the known reaction of isocyanates and cyanamide (Nl CN). For example, N-cyano-N -phenyl urea has been synthesized from phenyl isocyanate and an aqueous alkaline solution of cyanamide in high yield.(3) Recently, similar reactions were used to prepare various di-N-cyanourea compounds from diisocyanates. ( 1) These monomers were also synthesized directly by reacting diisocyanates with cyanamide at melt temperatures. 

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