Production of Potentially Prebiotic Condensed Phosphates by Phosphorus Redox Chemistry (original) (raw)

Abstract

Supporting Information Experimental Section Fenton Chemistry: A series of solutions were prepared with Na 2 HPO 3 or NaH 2 PO 2 in concentrations between 0.001 M to 0.1 M, iron (as FeCl 2 × 4H 2 O or as FeSO 4) concentrations between 0.001 M to 0.1 M, and H 2 O 2 concentrations between 0.002 M to 0.5 M (Table S1), each with a starting pH of 7±1, unless otherwise noted. Peroxide was added last to promote the reactions. One experiment was performed with a formaldehyde concentration of 1.2 M to act as a reductant. The solutions were stirred for 1-20 days, a 2 mL aliquot of each solution was extracted and placed in 2 mL of a 1:1 mixture of 10 M NaOH solution and D 2 O to quench the reaction, precipitate Fe III and prepare the sample for analysis by NMR. Decanted samples were analyzed using 31 P NMR on a Varian 300 four-nucleus probe FT-NMR spectrometer at 121.43 MHz and 24.5 ºC for 256 to 6000 scans following prior work [6a,c] , or on a Bruker Avance 500 four-nucleus FT-NMR system operating at 25°C and 202.46 MHz for phosphorus with 400-9000 scans. Spectra were acquired in both 1 H-decoupled and coupled modes. The peaks were identified based on comparison to known standards and previous work, with abundances determined from peak areas. [6,15] From these data, we determine that approximately 34.5% of reduced P becomes oxidized to condensed P (Fig. S1, vide infra). Some solutions were prepared with a starting solution pH of 13. In these experiments, the Fe II precipitated to green rust and did not promote any Fenton chemistry. These solutions also showed no oxidation of reduced compounds. From these experiments, we determined that the reactions were quenched by addition of base to the solution, hence the addition of NaOH does not promote further reaction of phosphorus species.

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