Cyanide tetramer

Under certain conditions hydrogen cyanide can polymerize to black soHd compounds, eg, hydrogen cyanide homopolymer [26746-21-4] (1) and hydrogen cyanide tetramer [27027-02-2], C H N (2). There is usually an incubation period before rapid onset of polymer formation. Temperature has an inverse logarithmic effect on the incubation time. Acid stabilizers such as sulfuric and phosphoric acids prevent polymerization. The presence of water reduces the incubation period. 

Hydrogen cyanide tetramer (Z-) 2,3-dianaino-2-butenedinitdle [1187-42-4] (15), an a2acyanocarbon, is produced by Nippon Soda in pilot-plant quantities for development as a chemical intermediate (66,67). On oxidation it forms 2,3-diiminobutanedinitrile [28321-79-7] (16) (68). These two, in turn, combine to give pyra2ine—tetracarbonitnle [33420-37-0] (69). 

Hydrogen cyanide tetramer is strongly adsorbed on acti-... 

The present procedure is a modification of the original synthesis.3 Hydrogen cyanide tetramer can be prepared directly from hydrogen cyanide.4... 

This is a convenient laboratory preparation of hydrogen cyanide tetramer that avoids the hazards in using hydrogen cyanide itself. Hydrogen cyanide tetramer is a useful intermediate for the synthesis of heterocycles such as imidazoles5- 6 and thiadiazoles.7... 

In a similar reaction it is also reported that 4,8-diaminopyrimido[5,4-d]pyrimidine is formed in the reaction of hydrogen cyanide with liquid ammonia. This reaction also presumably proceeds by way of the hydrogen cyanide tetramer, diaminomaleonitrile... 

A nucleophilic attack on the coordinated cyanide by a free cyanide, Reaction 14, which yields directly one of the precursors of the cyanide tetramer in Reaction 12. This mechanism is consistent with the... 

Bredereck and Schmotzer (1044), from diaminomaleonitrile (DAMN hydrogen cyanide tetramer) and oxalyl chloride, prepared 2,3-dicyano-5,6-dihydroxy-pyrazine but Stetten and Fox (1049) could not prepare 23-diamino-5-hydroxy-pyrazine from glycine amide and oxamide. Section 11.3 lists preparations from a, -diamino or a, -diimino compounds and reagents other than a,0-dicarbonyl compounds (384) with additional data (1050) and oxidation of 23-dichloro-quinoxaline with hot aqueous potassium permanganate gave 23-dicarboxy-5,6-dihydroxypyrazine (1051). 

Chang, S., Flores, J. and Ponnamperuma, C. (1969) Peptide formation mediated by hydrogen cyanide tetramer a possible prebiotic process. Proc. Nat. Acad. Sci. U.S. 64, 1011-1015. 

In all cases where the structure has been determined, the Au attains planar four-fold coordination and polymerizes as appropriate to achieve tliis. The halides for instance are dimeric but with the cyanide, which forms linear rather than bent bridges, tetramers are produced ... 

Diaminomaleonitrile (DAMN) 133, a tetramer of hydrogen cyanide, is an important precursor for the synthesis of pyrazine-2,3-dicarbonitriles 134 (Scheme 36 Table 2). The condensation with a-diketones proceeds at room temperature or by warming for a short time. 

Four tetramers of hydrogen cyanide have been isolated the well-known diaminomaleonitrile (DAMN), diaminofumaronitrile, 4-amino-5-cyano-imidazole, and an HCN adduct of s-triazine. 

A further possibility is that tetramer formation may have occurred in an eutectic solution. High yield of tetramer (> 10%) can be obtained by cooling dilute cyanide solutions to between - 10°C and -30°C for a few months. 

The corresponding hydroxypyrazinecarboxamides (64) are synthesized by direct condensation of an a, -dicarbonyl compound with aminomalondiamide (63).112 A further example of this general synthetic method is the condensation of a,)3-dicarbonyl compounds with the tetramer of hydrogen cyanide (65) to give 2,3-dicyano-pyrazines (66).226,226... 

Figure 8.4 Mechanism of tetramerization of hydrogen cyanide leading to the formation of a stable tetramer diaminomaleonitrile. (Adapted from Orgel and Lohrman [24])...

The synthesis of various purine bases from hydrogen cyanide as the only carbon-containing substrate was documented by Orgel and coworkers [24]. The only stable precursor found in polymerization of hydrogen cyanide in concentrated (1-llmol/1) aqueous solutions is its tetramer, diaminomaleonitrile. It is easily formed in the reaction of hydrogen cyanide with ammonium cyanide (Figure 8.4). At the same time, in concentrated solutions of ammonium cyanide in the presence of ammonia, formamidine is formed ... 

Hydrogen cyanide, H-C=N , is a colorless, extremely toxic, volatile liquid, mp -13.4°C, bp -1-25.6 °C, with a high dielectric constant (107 at 25 °C). It functions as a weak acid Ka = 4.9 x 10 °). It is made by acidifying aqueous solutions of cyanides or industrially by the exothermic reaction of methane with ammonia in a fast flow/rapid quench system (equation 16). Hydrogen cyanide polymerizes readily nnder a variety of conditions hydrogen cyanide oligomers include the trimer aminomalononitrile and the tetramer diaminomaleonitrile (Figure 8). 

A number of metal carbonyls and cyanides, particularly those of nickel and iron, form 7r-complexes with alkynes. These systems behave cat-alytically in the carbonylation of acetylene and in the formation of trimers (benzene) and tetramers (cyclooctatetraene). 

Diaminomaleonitrile (1) is formed as a stable tetramer from hydrogen cyanide. The formation of the tetramer is enhanced in dilute solution and at low temperature. 

---