Interaction of 2-amino, 3-amino and 4-aminopyridines with nickel and cobalt ferrocyanides

Interaction of aromatic amines with iron oxides: implications for prebiotic chemistry

The interaction of aromatic amines (aniline, p-chloroaniline, p-toludine and p-anisidine) with iron oxides (goethite, akaganeite and hematite) has been studied. Maximum uptake of amines was observed around pH 7. The adsorption data obtained at neutral pH were found to follow Langmuir adsorption. Anisidine was found to be a better adsorbate probably due to its higher basicity. In alkaline medium (pH > 8), amines reacted on goethite and akaganeite to give colored products. Analysis of the products by GC-MS showed benzoquinone and azobenzene as the reaction products of aniline while p-anisidine afforded a dimer. IR analysis of the amine-iron oxide hydroxide adduct suggests that the surface acidity of iron oxide hydroxides is responsible for the interaction. The present study suggests that iron oxide hydroxides might have played a role in the stabilization of organic molecules through their surface activity and in prebiotic condensation reactions.

Possible role of metal(II) octacyanomolybdate(IV) in chemical evolution: interaction with ribose nucleotides

We have proposed that double metal cyanide compounds (DMCs) might have played vital roles as catalysts in chemical evolution and the origin of life. We have synthesized a series of metal octacyanomolybdates (MOCMos) and studied their interactions with ribose nucleotides. MOCMos have been shown to be effective adsorbents for 5'-ribonucleotides. The maximum adsorption level was found to be about 50 % at neutral pH under the conditions studied. The zinc(II) octacyanomolybdate(IV) showed larger adsorption compared to other MOCMos. The surface area seems to important parameter for the adsorption of nucleotides. The adsorption followed a Langmuir adsorption isotherms with an overall adsorption trends of the order of 5'-GMP > 5'-AMP > 5'-CMP > 5'-UMP. Purine nucleotides were adsorbed more strongly than pyrimidine nucleotides on all MOCMos possibly because of the additional binding afforded by the imidazole ring in purines. Infrared spectral studies of adsorption adducts indicate that adsorption takes place through interaction between adsorbate molecules and outer divalent ions of MOCMos.

Interaction of ribonucleotides with metal hexacyanocobaltate(III): a possible role in chemical evolution

It has been proposed that metal cyanide complexes would have acted as effective prebiotic catalysts. Insoluble metal cyanide complexes could have concentrated biomonomers from the dilute prebiotic soup, facilitating certain prebiotic reactions. In the light of the above hypothesis, interaction of four ribonucleotides, namely 5'-AMP, 5'-GMP, 5'-CMP, and 5'-UMP with copper(II)- and cadmium(II) hexacyanocobaltate(III) has been studied. The interaction was found to be maximum at neutral pH. 5'-GMP showed greater interaction with both the metal hexacyanocobaltate(III) while copper(II) hexacyanocobaltate(III) showed greater uptake than cadmium(II) hexacyanocobaltate(III) for all the four ribonucleotides studied. Infrared spectral studies of ribonucleotides, metal hexacyanocobaltate(III) and ribonucleotide - metal hexacyanocobaltate(III) adducts indicated that the nitrogen base and phosphate moiety of ribonucleotides interact with outer divalent metal ion present in the lattice of metal hexacyanocobaltate(III).

Interaction of tryptophan and phenylalanine with metal ferrocyanides and its relevance in chemical evolution

The interaction of two naturally occurring aromatic alpha-amino acids, namely, tryptophan and phenylalanine, with zinc, nickel, cobalt, and copper ferrocyanides has been studied. Both amino acids showed a high adsorption affinity toward metal ferrocyanides at neutral pH (7.0). Adsorption trends followed the Langmuir adsorption isotherm. Values of the Langmuir constants K(L) and X(m) suggest tryptophan is a better adsorbate than phenylalanine. Zinc ferrocyanide showed the highest adsorption, while the minimum adsorption was found in the case of copper ferrocyanide. Infrared spectral studies of adsorbate, adsorbent, and adsorption adducts indicate that adsorption occurs because of the interaction of adsorbate molecules with outer divalent metal ions present in the lattice of metal ferrocyanides. The present investigation supports the hypothesis that metal ferrocyanides might have concentrated the biomonomers on their surface in primeval seas during the course of chemical evolution.

Adsorption and Oxidation of Aniline and Anisidine by Chromium Ferrocyanide

The interaction of aniline and p-anisidine with chromium ferrocyanide has been studied. Maximum uptake of both anilines was observed around pH 7. The adsorption data obtained at neutral pH were found to follow Langmuir adsorption. Anisidine was a better adsorbate because of its higher basicity. In alkaline medium (pH>8) both aniline and anisidine reacted with chromium ferrocyanide to give colored products. Analysis of the products by GC-MS showed benzoquinone and azobenzene as the reaction products of aniline while p-anisidine afforded a dimer. IR analysis of the amine-chromium ferrocyanide adduct suggests that the outer metal ion of chromium ferrocyanide and amino group of amines are responsible for the interaction. A possible reaction mechanism for the product formation in alkaline medium has been proposed. The present study suggests that metal ferrocyanides might have played an important role in the stabilization of organic molecules through their surface activity in the prebiotic condensation reactions.