Chemical evolution. 31. Mechanism of the condensation of cyanide to hydrogen cyanide oligomers

Abstract

Diamincimaleonitrile undergoes a rapid Ni(I1)-catalyzed or a much slower uncatalyzed decomposition to yield 2 equiv of cyanide. This is not an equilibration between diaminomaleonitrile and the dimer and trimer of HCN as shown by the absence of incorporation of H13CN when incubated with diaminomaleonitrile. The formation of urea and oxalic acid is enhanced and the steady-state concentration of diaminomaleonitrile is decreased when the oligomerization of HCN is performed in the presence of oxygen as compared to a pure nitrogen atmosphere. Small but significant yields of oxalic acid and urea were observed when oxygen was eliminated from the reaction solution. An oligomerization pathway is proposed which is consistent with these data. These findings are not consistent with the proposal that HCN condenses to heteropolypeptides via azacyclopropenylidene imine.Hydrogen cyanide oligomers are believed to have had a significant role in the prebiotic synthesis of purines, pyrimidines, and amino HCN condenses in a stegwise fashion to the dimer 1, trimer 2, and tetramer 3. It was pos-tulated that one or more of these simple HCN derivatives condenses further to yield HCN oligomers, a complex mixture of substances with a molecular weight of 500-1000. Purines, pyrimidines, and amino acids are released on hydrolysis of these oligomers. The oligomerization reaction is dependent only on the pH of the reaction mixture and is independent of added nucleophile.4 Urea and oxalic acid are also products of the oligomerization reaction. An investigation of the me chanism of formation of the oligomers was undertaken because these substances may have had a central role in the formation of biomolecules on the primitive earth. Results and DiscussionThe Proposed Equilibrium between Diaminomaleonitrile (3) and Aminomalononitrile (2). We proposed previously that the monomer, dimer ( l ) , trimer (2), and tetramer (3) of HCN readily equilibrate in aqueous ~o l u t i o n .~ The formation of a precipitate of AgCN when Ag+ is added to an aqueous solution of 3 provided support for this h y p o t h~s i s .~ The observation that diaminomaleonitrile releases cyanide 0022-326317811943-3989$01 .OO/O rapidly when treated with Ni2+ in NH40H solution, a method for the determination of cyanide ion, prompted a reinvestigation of the equilibrium proposed between 1,2, and 3. The catalyzed decomposition of diaminomaleonitrile requires the presence of both Ni2+ and NH3 if it is to proceed a t a rapid rate. Approximately 2 equiv of cyanide are released per mole of diaminomaleonitrile. If diaminomaleonitrile is in equilibrium with HCN, 4 equiv of cyanide would be detected as the Ni(CN)42-complex. The same yield of cyanide is obtained when the hydrolysis proceeds 4 X times slower in the absence of Ni2+. The similar yields of HCN in the catalyzed and uncatalyzed reactions suggest that overall decomposition pathways are the same in both reactions.The mechanisms of both the Ni2+-catalyzed and -uncatalyzed decomposition of diaminomaleonitrile are unclear. Hydrolysis of 3 ...

Quantification of Diaminomaleonitrile Using High Performance Liquid Chromatography with UV and Electrospray Ionization Mass Spectrometric Detection

“…Spectrophotometry alone, however, is nonspecific, and may include absorption from other UV-absorbing compounds. As noted in Ferris and Edelson (1978), polymerizing solutions of cyanide produce a variety of UV-absorbing compounds (e.g., Fig. 2).…”

The adsorption and reaction of adenine nucleotides on montmorillonite

“…DAMN was obtained from Aldrich and was recrystallized from water (mp 178-179°C) (Ferris and Edelson, 1978). Cupric chloride and cupric nitrate were obtained from Maltinckrodt (Analytical Reagents) and manganese chloride was a Baker-Analyzed reagent.…”

Bildung von Aminosäurevorprodukten in Zeolith X / Formation of Aminoacid Precursors in Zeolithe X

“…Überraschenderweise entstand bei der Umsetzung von AA mit NH4CN und der nachfolgenden sauren Hydrolyse nicht nur Alanin, sondern auch Glycin. Dessen Entstehung kann auf das HCN-Tetramere Diaminomaleinsäuredinitril NC-C(NH2):C(NH2)CN zurückgeführt werden, von dem bekannt ist, daß es hydrolytisch in Aminoacetonitril und das Amidnitril der Oxalsäure (Cyanformamid) gespalten werden kann [16,17] Photochemischer Ringbrenner PCQ-X1 der Fa. Ultra-Violet Prod.…”