Nitrogen cyanamid

Before the development of the cyanamide process for the fixation of nitrogen, cyanamide was prepared by the interaction of cyanogen chloride er bromide (from the action of the halogen on potassium cyanide) with ammonia in water or ether solution. 

Total nitrogen Nitrate nitrogen Ammoniacal nitrogen Ureic nitrogen Cyanamide nitrogen... 

Also known as nitrolim and lime nitrogen. The fresh product contains approximately 55 per cent, of calcium cyanamide, 20 p>er cent, of lime, 12 per cent, of graphite and small amounts of other impurities. It should be protected from moisture when stored in order to prevent slow polymerisation to dicyano-diamide. 

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). 

The nitrogen of aHphatic and aromatic amines is alkylated rapidly by alkyl sulfates yielding the usual mixtures. Most tertiary amines and nitrogen heterocycles are converted to quaternary ammonium salts, unless the nitrogen is of very low basicity, eg, ia tn phenylamine. The position of dimethyl sulfate-produced methylation of several heterocycles with more than one heteroatom has been examined (22). Acyl cyanamides can be methylated (23). Metal cyanates are converted to methyl isocyanate or ethyl isocyanate ia high yields by heating the mixtures (24,25). 

Preparation. Hexagonal boron nitride can be prepared by heating boric oxide with ammonia, or by heating boric oxide, boric acid, or its salts with ammonium chloride, alkaU cyanides, or calcium cyanamide at atmospheric pressure. Elemental nitrogen does not react with boric oxide even in the presence of carbon, though it does react with elemental boron at high temperatures. Boron nitride obtained from the reaction of boron trichloride or boron trifluoride with ammonia is easily purified. 

Calcium cyanamide (lime nitrogen) has been used as a fertiliser (6). It hydrolyses ia moist soil to produce ammonia ... 

Reaction With Nitrogen. Calcium cyanamide is produced from calcium carbide... 

In North America, calcium cyanamide is no longer used as fertiliser, but it has limited use in special agricultural appHcations for defoHants, fungicides, herbicides, and as a weed killer. The primary industrial use is as a chemical intermediate for the manufacture of calcium cyanide, hydrogen cyanamide solution, and dicyandiamide. Calcium cyanamide is also used to add nitrogen to steel. 

A 1990 study by American Cyanamid Co. demonstrated that the reaction cycle depends also on the supply pressure of the gaseous nitrogen. The 3-d reaction cycle at the normal 75 Pa (0.3-ia. water) pressure can be reduced to 2.4 d usiag the N2 gas pressure at 2 kPa (8-ia. water) iato the oveas (19). 

No reaction takes place below 500°C when sodium cyanide and sodium hydroxide are heated in the absence of water and oxygen. Above 500°C, sodium carbonate, sodium cyanamide [19981-17-0] sodium oxide, and hydrogen are produced. In the presence of small amounts of water at 500°C decomposition occurs with the formation of ammonia and sodium formate, and the latter is converted into sodium carbonate and hydrogen by the caustic soda. In the presence of excess oxygen, sodium carbonate, nitrogen, and water are produced (53). 

Calcium cyanamide hy action of atmospheric nitrogen on calcium carbide... 

Acetylene and ethylene compete as a chemical raw material. Ethylene is generally more economical, resulting in declining use of acetylene as a raw material. Calcium carbide, a raw material for acetylene has other uses. Treated with nitrogen, it gives calcium cyanamide, valuable as a fertilizer and weed killer, and a raw material for the production of melamine, used ir ng some modern plastics. 

The basic chemical of the cyanamide industry is calcium cyanamide CaNCN, mp 1340°, obtained by nitrogenation of CaCi. 

CaNCN is used as a direct application fertilizer, weed killer, and cotton defoliant it is also used for producing cyanamide, dicyandiamide and melamine plastics. Production formerly exceeded 1.3 million tonnes pa, but this has fallen considerably in the last few years, particularly in the USA where the use of CaNCN as a nitrogenous fertilizer has been replaced by other materials. In 1990 most of the world s supply was made in Japan, Gennany and Canada. 

Somewhat above their melting points the aminothiatriazoles decompose more or less violently. When they are heated in aqueous solution nitrogen and sulfur are formed together with a cyanamide (isolated by Freund and Schwarz as the trimeric melamines) [Eq. (18)]. With the unsubstituted 5-aminothiatriazole the reaction... 

The influence of nitrogen fertilizer source on the germination rate of ergots placed on the ground in rye culture has been studied. Compared with calcium ammonium nitrate, application of calcium cyanamide reduced the germination of ergots and formation of perithecia by 40-50% (Mielke, 1993). 

Like the Haber process for the synthesis of ammonia, this reaction represents a way of converting elemental nitrogen into a compound (nitrogen fixation). Moreover, calcium cyanamide reacts with steam at high temperature to yield ammonia,... 

Although relatively few compounds contain only carbon and nitrogen, derivatives such as the cyanides have commercially important uses. Also, calcium cyanamide, CaCN2, can be prepared by the reaction... 

B There are a total of sixteen valence electrons in the cyanamide molecule (five from each nitrogen atom, four from carbon and one electron from each hydrogen atom). The formula has been written as NH2CN to remind us that carbon, the most electropositive p-block element in the compound should be selected as the central atom in the skeletal structure. 

Frank-Caro Also called the Cyanamide process. An early process for fixing atmospheric nitrogen. Lime and carbon were heated to produce calcium carbide this was reacted with nitrogen to give calcium cyanamide, which was hydrolyzed with steam to yield ammonia and calcium carbonate. Developed by A. Frank and N. Caro from 1895 at Dynamit, Germany, and used in Germany, Norway, and Italy until it was replaced by the Haber-Bosch process after World War I. 

France. See also French Patent Office aquaculture production, 3 189t piezoelectric ceramics research, 1 708 regenerated cellulose fibers in, 11 249 Franck-Condon shift, 22 215 Frank-Caro cyanamide process, 17 292 Frankia species, in nitrogen fixation, 17 299... 

When calcium carbinde is made to react with nitrogen calcium cyanamide is produced which on acid hydrolysis yields cyanamide. Cyanamide on heating to 100°C yields dicyanamide which on heating above its Melting point yields melamine. 

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