Structural studies on HCN oligomers

Ferris, James P.; Edelson, E. H.; Auyeung, J. M.; Joshi, P. C.

doi:10.1007/bf01732676

Cited by 46 publications

(18 citation statements)

References 24 publications

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“…In 1923, Bedel 8 argued that the stable oligomer formed by HCN is a tetramer rather than the previously proposed trimer. 9,10 More recently, Ferris and co-workers [3][4][5] found that ͑in water͒ DAMN forms irreversibly from hydrogen cyanide. In fact, we find that all of the narrow signals in our dark, base-catalyzed product ͓Figs.…”

Section: Discussionmentioning

confidence: 99%

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HCN polymers characterized by solid state NMR: Chains and sheets formed in the neat liquid

Mamajanov

Herzfeld

2009

The Journal of Chemical Physics

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Hydrogen cyanide polymerizes readily under a variety of conditions and significant prebiotic roles have been suggested for these polymers due to the abundance of HCN in universe. However, the structures of HCN polymers have been more speculative than grounded in experimental data. Here we show that 13 C and 15 N solid state NMR spectra of polymers formed in neat HCN are inconsistent with the previously proposed structures and suggest instead that the polymers are formed by simple monomer addition, first in head-to-tail fashion to form linear, conjugated chains, and then laterally to form saturated two-dimensional networks. This interpretation of the NMR spectra finds support in other information about the polymerization of neat HCN, including the presence of free radicals. As expected from the literature, formation of the HCN tetramer, diaminomaleonitrile, is also observed, but only when the reaction is catalyzed exclusively by base and then in crystalline form.

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Section: Discussionmentioning

confidence: 99%

“…However, the structures of these polymers remain unknown despite extensive effort. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Figures 1 and 2 show the proposed polymer structures. The "ladder" structures in Fig.…”

Section: Introductionmentioning

confidence: 99%

HCN polymers characterized by solid state NMR: Chains and sheets formed in the neat liquid

Mamajanov

Herzfeld

2009

The Journal of Chemical Physics

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“…Moreover, what appear to be similar materials can be produced by an electrical discharge in gaseous HCN, or by adding base to liquid HCN (Mathews 1992, Minard et al 1998. In general, the polymeric materials formed in these reactions seem to be heterogeneous in color, structure, and chemical properties depending on the conditions under which the polymer is formed (Ferris et al 1981, Liebman et al 1995, Minard et al 1998. Minard et al (1998) have used a variety of experimental techniques to probe the structure of HCN polymers and shown that these polymers can yield several nitrogen heterocycles, including adenine derivatives closely related to biologically important molecules.…”

Section: Introductionmentioning

confidence: 99%

Exploring the structure of a hydrogen cyanide polymer by electron spin resonance and scanning force microscopy

et al. 2003

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Summary: Aqueous solutions of potassium cyanide and ammonium hydroxide are known to yield a heterogeneous cyanide polymer, containing paramagnetic sites and biologically significant substructures including polypeptides. Here, such solutions were used to prepare various samples of polymer for study by X-band and W-band electron spin resonance (ESR), scanning electron microscopy (SEM), and scanning force microscopy (SFM). Elemental composition of a typical sample of the polymer was C-35.2%, N-38.47%, O-14.51%, and H-4.13%, exposing the polymer to 6M HCl hydrolyzed portions of the polymer and released glycine and traces of other amino acids. The X-band ESR spectra consist of a single slightly asymmetric line centered at g = 2.003; spin concentration measurements made at X-band using a nitroxide radical standard yield approximate radical concentrations of 10 18 spins/gm. W-band ESR indicates the presence of a single rhombic paramagnetic site with g x = 2.0025, g y = 2.0030, and g z = 2.0048 and the possibility of small 14 N hyperfine splittings. The ESR spin echo studies yield a longitudinal relaxation time, T 1, of 75 µS and a short-phase memory relaxation time, T m , of about 300 nS. Scanning electron microscopy studies of the polymer show that it is made of ellipsoidal particles about one micron in size. The particles tend to clump together when suspended in aqueous solution. The particles disperse and dissolve in dimethyl sulfoxide (DMSO); when these solutions dry on microscope slides, optical microscopy shows a branched island morphology for the polymer. This morphology is reminiscent of snowflakes and is identified as dendritic. Phase contrast SFM of the dendritic arms show a striking segregation and ordering of various components of the polymer. Paramagnetic sites are conserved in the series of steps leading to dendritic structures.

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“…[1][2][3][4][5] One of most intriguing proposals, 2 based on observations of ␣-amino acids in polymer hydrolysates, suggests the formation of protopeptides by acid-base polymerization of the HCN trimer, aminomalononitrile. However, our previous NMR study 6 showed that protopeptide is not formed in the polymerization of neat HCN.…”

Section: Introductionmentioning

confidence: 99%

HCN polymers characterized by SSNMR: Solid state reaction of crystalline tetramer (diaminomaleonitrile)

Mamajanov

Herzfeld

2009

The Journal of Chemical Physics

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The HCN tetramer, diaminomaleonitrile, crystallizes in sheets with amine and nitrile groups of neighboring molecules in close proximity. This suggests the possibility of relatively facile acid-base addition to form a protopeptide polymer. We find that moderate heating under argon indeed results in an unmistakable reaction, with the abrupt transformation of pale crystallites to shrunken dark particles that become electrically conductive upon doping with iodine. Since nearly a quarter of the mass is lost in the process and the released gas condenses, polymerizes, and reacts with aqueous AgNO 3 like HCN, it seems likely that the dark solid is a polymer of HCN trimer.13 C and 15 N solid state NMR spectra show the formation of new N-C bonds, and entirely different functional groups from those observed in polymers formed by liquid HCN. These include three different types of nitrogen functionalities and an absence of saturated carbon or nitrile. The observed chemical shifts, optical properties, and electrical conductivity are consistent with polymers of HCN trimer that have undergone cyclization to form poly-͓aminoimidazole͔.

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Structural studies on HCN oligomers

Cited by 46 publications

References 24 publications

HCN polymers characterized by solid state NMR: Chains and sheets formed in the neat liquid

HCN polymers characterized by solid state NMR: Chains and sheets formed in the neat liquid

Exploring the structure of a hydrogen cyanide polymer by electron spin resonance and scanning force microscopy

HCN polymers characterized by SSNMR: Solid state reaction of crystalline tetramer (diaminomaleonitrile)

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