Biurets synthesis

The common method of preparation of 6-alkyl-2,4-dioxotetrahydro-triazines is the cyclization of acyl-biurets by aqueous hydroxide. Formyl biuret which should by analogy 3deld 5-azauracil had not been known until recently. Its transient formation can be expected during further synthesis of 5-azauracil. Piskala and GuP achieved... 

Works on the oxidation of uric acid has unequivocally established the triazine structure > ° (9) of oxonic acid. This is further confirmed by the straightforward synthesis described by Piskala and Gut. ° The reaction of biuret (11) with potassium ethyloxalate yielded a potassium salt (24), that with ethyl oxamate, the amide of oxonic acid (25). Both these compounds were converted to 5-azauracil. An analogous reaction with diethyloxalate which should produce an ester of oxonic acid resulted in a mixture of urethane and parabanic acid, however. 

Bisphenol-A benzoxazine reaction, under acidic conditions, 416-417 Bisphenol-A polyarylates, 77 synthesis of, 109-113 Bisphenol-A polysulfone, 327 nucleophilic synthesis of, 337 Bisphenolic monomer, 354 Biurets, 227... 

The reaction has been extended to the synthesis of the analogous 3-alkylthio heterocycles (123) from the appropriate dithiobiurets (122).132 1-Substituted 2,4-dithiobiurets (125), unlike their monothio-biuret analogs (118), are unsuitable as precursors of 1,2,4-thiadiazoles, since in any oxidation the two thiol groups may be expected to react preferentially, resulting in the formation of cyclic disulfides (126). The formulation of such oxidation products as 1,2,4-thiadiazoles has indeed been discussed by Bambas1 however, the available evidence133 favors the cyclic disulfide structure.134... 

Triazinedione is synthesized from formylbiuret (85 Scheme 51) (60AG836). The latter compound has been postulated as an intermediate in the reaction of biuret with ethyl formate (61CCC2519). The synthesis is also effected by treatment of A AT -dicarbamoylform-amidine (86) with sodium ethoxide (Scheme 51). 

Fig. 7.7. Laboratory method for the synthesis of adipic acid dinitrile (D). Condensation of adipic acid (B) and urea to give adipic acid diamide (E) and its thermal dehydration. The reaction F — H—as well as its mechanism—corresponds to the reversal of the formation of biuret that takes place upon the heating of urea (mechanistic details conversion of M —> 0 in Figure 8.3).

Any finishing can be coupled with the synthesis prilling and granulation, both direct or via crystallization. Different product quality (biuret, moisture, hardness and size) are obtained according to client requests. 

Nonprotein nitrogenous sources include urea, biuret, and ammoniated feeds. These compounds are cheap sources of the nitrogen required by the animals for protein synthesis. Nonprotein nitrogen poisoning is a common problem and is often seen in animals not gradually introduced to diets containing these compounds. It is an acute fatal condition characterized by bloating, intense abdominal pain, ammonia... 

HOCN will also react with ammonia (Wohler s synthesis) to give urea, and with biuret to give ammelide [2168]. The intermediacy of HOCN was confirmed in 1936, when the salts... 

A tailored modifier does not always have to be deliberately added to a crystallizing system it may already exist, e.g., as a synthesis by-product of a chemical reaction. If its presence causes a crystal habit problems, it must be removed or deactivated. On the other hand, it may have a beneficial effect. These are both commonly encountered cases in the manufacture of organic chemicals. A simple, but industrially important, example is the effect of biuret on the crystallization of urea (Davey, Fila and Garside, 1986). In the synthesis of urea (NH2CONH2) from ammonia and carbon dioxide a small amount of biuret (NH2CONHCONH2), a condensation dimer, is formed. The presence of biuret is actually beneficial because from pure aqueous solution urea crystals form as elongated [001] needles that are difficult to process. Biuret retards growth in the... 

At least 15 processes have been proposed for the synthesis of polyureas with the repeat unit —R—NH—CO—NH—. Most of these are unsuitable for commercial production because of side reactions. For example, in the conversion of diisocyanates with diamines, biuret groups readily occur, and therefore, cross-linked polymers (see also Section 28.4). Polymers from the reaction of diamines with COS cannot be obtained free of sulfur, etc. 

Abdelhady et al, reported the thermolysis of single source precursors for the synthesis of ultrasmall indium sulfide nanorods and nanowires. In their synthesis, indium(iii) complex of l,l,5,5-tetra-iso-propyl-2-thio-biuret was heated with oleylamine at three different temperatures. XRD patterns of the materials isolated by this method showed diffraction peaks corresponding to tetragonal p-In2S3. TEM images revealed that the material synthesized at different temperatures and different concentration of precursors is composed of very thin nanorods and nanowires with widths and lengths of less than 1 nm and 12 nm, respectively. 

Texas) in 1964 and 1965. Toyo also will provide the acoustic vibration unit. In prilling, the urea melt is concentrated via vacuum evaporation to 99.8% and fed as quickly as possible into the bucket to minimize biuret formation. The liquid forms drops that then fall down a cylindrical concrete tower that has either induced, forced, or natural draft air flow. The prills solidify and are removed at the bottom by belt conveying to storage. Some plants have a fluidized-bed cooler in the prill tower bottom and others use an in-line cooler before storage. If low biuret product is to be produced, the urea melt from the last decomposition stage of the synthesis plant is first crystallized and the crystals are then melted just before prilling. 

The byproducts biuret and cyanuric acid are observed in the largest quantity at low and moderate temperatures up to about 300 °C [36] however, additional byproducts form in smaller amounts as shown in Fig. 16.2 [11, 36, 37]. Substitution of the OH groups of cyanuric acid by NH3 yields the more stable triazines ammelide, ammeline, and melamine [36]. Ammelide may also be formed by the reaction of biuret with HNCO, if water is eliminated instead of NH3 [11]. Melamine may also be produced by trimerization of cyanamide [36] since cyanamide is an intermediate in melamine synthesis [35]. Cyanamide was not observed in a... 

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