Dicyanodiamides

Di- and tri-chloroacetamide, oxamide, guanidine, and cyanoguanidine (dicyanodiamide) do not give satisfactory results. 

Heating dicyanodiamide, either with ammonia or on its own under pressure. 

Of these methods the first named was for many years the most important commercially. Dicyanodiamide ( dicy ) is prepared by heating cyanamide solution at 70-80°C. The cyanamide itself is prepared from calcium cyanamide Figure 24.5). 

It will be noted that dicyanodiamide is the dimer of cyanamide and melamine is the trimer. 

The products of the diacetylene and ethyldiacetylene cyclization with dicyanodiamide are 2-cyanamino-4-alkylpyrimidines (34) (80°C, EtONa, EtOH, 14 h, yield 39%) (71ZOR14). 

According to an O.S. amendment sheet, the procedure as described [1] is dangerous because the reaction mixture (dicyanodiamide and ammonium nitrate) is similar in composition to commercial blasting explosives. This probably also applies to similar earlier preparations [2]. An earlier procedure which involved heating ammonium thiocyanate, lead nitrate and ammonia demolished a 50 bar autoclave [3], TGA and DTA studies show that air is not involved in the thermal decomposition [4], Explosive properties of the nitrate are detailed [5], An improved process involves catalytic conversion at 90-200°C of a molten mixture of urea and ammonium nitrate to give 92% conversion (on urea) of guanidinium nitrate, recovered by crystallisation. Hazards of alternative processes are listed [6],... 

The baking process has remained much the same until the present day at a stoichiometric ratio of 1 4, phthalic anhydride or phthalic acid reacts with an ammonia releasing compound. The reaction may also start from other suitable materials, such as phthalic acid derivatives, including phthalic acid esters, phthalic acid diamide, or phthalimide. Appropriate ammonia releasing agents include urea and its derivatives, such as biuret, guanidine, and dicyanodiamide. The fact that a certain amount of urea decomposes to form side products makes it necessary to use excess urea. Approximately 0.2 to 0.5, preferably 0.25 equivalents of copper salt should be added for each mole of phthalic anhydride. 0.1 to 0.4 moles of molybdenum salt per mole of phthalic anhydride is sufficient. The reaction temperature is between 200 and 300°C. 

Melamine (cyanuramide) is obtained by heating dicyanodiamide (structure 17.20), which is obtained by heating cyanamide. Melamine, which is used for the production of melamine-formaldehyde resins, is also obtained by heating urea (structure 17.21)... 

Chloroguanide Chloroguanide, A -(4-chlorophenyl)-A -isopropylbiguanide (37.1.3.2), is made from 4-chloroaniline and sodium dicyanoamide, the interaction of which results in the formation of (4-chlorophenyl)dicyanodiamide (37.1.3.1). Reacting this with isopropylamine gives the desired chloroguanide [30-32]. 

Brandimarte (Ref 3) describes the prepn of ASN, as follows PETN (20 parts) was added at 115-18° to a binary mixt of 70 ps AN and 10 ps dicyanodiamide, which had been previously fused for 6-8 hrs. The mixt was analyzed and found to contain ca 2% of GuN and ca 6% of biguanide nitrate, which were formed by interaction betw dicyanodiamide and AN... 

At alkaline pH, however, the dimerization of cyanamide to dicyanodiamide is favored. Dicyanodiamide acts as a corrosion inhibitor ... 

In Chapter 2 the DSC technique is discussed in terms of instruments, experimental methods, and ways of analysing the kinetic data. Chapter 3 provides a brief summary of epoxy resin curing reactions. Results of studies on the application of DSC to the cure of epoxy resins are reviewed and discussed in Chapter 4. These results are concerned with the use of carboxylic acid anhydrides, primary and secondary amines, dicyanodiamide, and imidazoles as curing agents. 

Most of the reported DSC studies involving base-catalysed cure are concerned with dicyanodiamide (DICY) which is a crystalline material, melting at 208 °C. At ambient temperature the solubility in epoxy resins is very low but above about 100 °C it is sufficiently soluble to initiate cure. DICY has free amino-hydrogen groups which can partake in addition reactions with epoxides ... 

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