Cyanamide hydrolysis

Direct synthesis from the elements has now displaced cyanamide hydrolysis to produce ammonia. 

Production of urea on a commercial scale did not assume much significance until about 1930. Early processes were based on calcium cyanamide hydrolysis in the presence of a base (Eqs. 11.56 and 11.57). 

By the hydrolysis of dialkyl cyanamides with dilute sulphuric acid this method gives pure secondary amines. The appropriate dialkyl cyanamide is prepared by treating sodium cyanamide (itself obtained in solution from... 

In 1880, R. Andreasch (52) confirmed the new formula (37) by preparing thiohydantoine through condensation of thioglycolic acid with cyanamide (the reverse reaction of the basic hydrolysis of thiohydantoin). 

The heat of hydration is approximately —70 kj /mol (—17 kcal/mol). This process usually produces no waste streams, but if the acrylonitrile feed contains other nitrile impurities, they will be converted to the corresponding amides. Another reaction that is prone to take place is the hydrolysis of acrylamide to acryhc acid and ammonia. However, this impurity can usually be kept at very low concentrations. American Cyanamid uses a similar process ia both the United States and Europe, which provides for their own needs and for sales to the merchant market. 

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. ... 

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-... 

Further work with the same dye (7.43) and carbodiimides (7.44 and 7.45) concentrated on this problem of limited efficiency. Cotton fabric padded with the dye phosphonate solution was aftertreated with the carbodiimide dissolved in various alcoholic solutions to avoid hydrolytic decomposition. Under these conditions cyanamide was much more effective than dicyandiamide. With conventional reactive dyes the efficiency of the dye-fibre reaction is limited by competing hydrolysis of the active dye. Although phosphonated or carboxylated reactive dyes do not hydrolyse, their level of fixation is limited by competing hydrolysis of the carbodiimide activator [46]. 

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. 

A second method is due to J. von Braun and consists in the addition of cyanogen bromide to tertiary cyclic bases.1 In the unstable addition product a C—N-linkage is broken and at the same time the bromine wanders to a new position. A brominated derivative of cyanamide is produced and this, on hydrolysis, yields a secondary amine which can be broken down further, e.g. 

Biguanides are accessible by a Grignard reaction of guanidinomagnesium halide with a substituted cyanamide, and hydrolysis of the resulting complex [59—61). The method is of considerable theoretical interest but so far only of limited practical importance. 

In the same context, successful utilization of cyanamide allowed the incorporation of the cyanoimino moiety of potential pharmacological properties (Scheme 17) [88]. In this case, the in situ hydrolysis of cyanamide into urea constimtes the comer stone of this four-component Biginelli-like reaction. 

Calcium cyanamide partially hydrolyzes to calcium hydrogen cyanamide, CaHCN2. The final hydrolysis products are calcium carbonate and ammonia. The reaction is slow, occurring in moist soil ... 

Elemental composition Ca 50.03%, C 14.99%, N 34.98. A measured amount of the compound is hydrolyzed with water. The product CaCOs is filtered, dried and determined by gravimetry. Calcium carbonate or the parent calcium cyanamide may be digested with nitric acid, diluted appropriately, and analyzed for Ca by AA or ICP spectroscopy. The hydrolysis product in solution, ammonia, may be measured by ammonium ion selective electrode, or by colorimetry followed by Nesslerization. 

However, hydrolysis of the oxime of 3-benzoyl-5-phenyl oxadiazole leads to benzoyl cyanamide (76). 

Thiourea (the sulphur analogue of urea) is the most commonly used sulphur precursor. In alkaline solution (in which depositions involving thiourea are carried out), the first step of the hydrolysis gives sulphide ions and cyanamide ... 

Nitroguanidine has weakly basic properties and this accounts for its ability to form salts with concentrated acids, e.g. it forms a sulphate with concentrated sulphuric acid. Nitroguanidine is hydrolysed on heating with concentrated sulphuric acid evolving nitrous oxide and carbon dioxide, the former probably derived from hydrolysis of nitramine and the latter from hydrolysis of cyanamide. The latter also yields ammonia on decomposition. 

Hydrolysis of cyanamides 6-13 Addition of ammonia to aldehydes 6-15 Reductive alkylation of ammonia or amines... 

Diomides. These compds are the dibasic acid derivs of ammonia or amines, and contain two -CONH2 groups. Numerous combinations of diacids, diamines, and amino acids have been interacted. Copolymers contg various proportions of two or more diacids have been prepd (Ref 2). The diamide of carbonic acid is called urea, H2NCONH2. It is a product of animal metabolism and is prepd industrially by reaction of CO2 with excess NH3 at high temp, or by an older method involving the hydrolysis of cyanamide (Ref 5)... 

Amino-1 //-1,2,4-triazole and its derivatives are frequently used as precursors for this ring via their reaction with suitable carbonyl compounds. The 5-amino-l,2,4-triazoles (27), prepared from calcium cyanide by hydrolysis to cyanamide followed by condensation with hydrazine (92MI4), reacted with the appropriate acetophenone in presence of ZnCl2 to give the... 

This substance forms salts with acids, and was first isolated in the form of its nitrate. The nitrate is not detonated by shock but undergoes a rapid decomposition with the production of light when it is heated. The picrate and the perchlorate explode violently from heat and from shock. Guanyl azide is not decomposed by boiling water. On hydrolysis with strong alkali, it yields the alkali metal salt of hydrazoic acid. It is hydrolyzed by am-moniacal silver nitrate in the cold with the formation of silver azide which remains in solution and of silver cyanamide which appears as a yellow precipitate. By treatment with acids or weak bases it is converted into 5-aminotetrazole. 

The preparation of pure symmetrical secondary amines (e.g. dibutylamine, Expt 5.199) is conveniently achieved by the hydrolysis of dialkylcyanamides with dilute sulphuric acid. The appropriate dialkyl cyanamide is prepared by treating sodium cyanamide (itself obtained from calcium cyanamide and aqueous sodium hydroxide solution) with an alkyl halide. In this case the reagent [ —C=N]20 may be regarded as a masked NH group. 

The complete decomposition of the cyanamide into calcium carbonate and ammonia may bo accomplished in stages by suitably arranging the conditions, so that the first substance to be formed is cyanamide itself, which is then transformed into urea, and the third stago involves the hydrolysis of urea into carbon dioxide and ammonia ... 

In connection with biosynthetic studies, compound (41) or (42) has been prepared, starting with OO-diacetyl-lycorine (37) (Scheme 6).13 Treatment of (37) with cyanogen bromide gave the cyanamide (38) in 80% yield this was not isolated but was directly oxidized to the aldehyde (39). Acetalization followed by reduction with lithium aluminium hydride gave the unstable amine (40), which upon hydrolysis gave a compound which, on the basis of its conversion into lycorine (37 OH in place of OAc) may be formulated as (41). This assignment is in doubt, since spectral evidence favours structure (42). 

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