Serpentinization-Associated Mineral Catalysis of the Protometabolic Formose System

Abstract

The formose reaction is a plausible prebiotic chemistry, famed for its production of sugars. In this work, we demonstrate that the Cannizzaro process is the dominant process in the formose reaction under many different conditions, thus necessitating a catalyst for the formose reaction under various environmental circumstances. The investigated formose reactions produce primarily organic acids associated with metabolism, a protometabolic system, and yield very little sugar left over. This is due to many of the acids forming from the degradation and Cannizaro reactions of many of the sugars produced during the formose reaction. We also show the heterogeneous Lewis-acid-based catalysis of the formose reaction by mineral systems associated with serpentinization. The minerals that showed catalytic activity include olivine, serpentinite, and calcium, and magnesium minerals including dolomite, calcite, and our Ca/Mg-chemical gardens. In addition, computational studies were performed for the first step of the formose reaction to investigate the reaction of formaldehyde, to either form methanol and formic acid under a Cannizzaro reaction or to react to form glycolaldehyde. Here, we postulate that serpentinization is therefore the startup process necessary to kick off a simple proto metabolic system-the formose protometabolic system.

Keywords: chemical complexity; chemical evolution; chemical garden; formose reaction; hydrothermal environments; metabolism; prebiotic chemistry; serpentinization; systems chemistry.

Scheme 1

The Mechanism of the Cannizzaro Reaction of Formaldehyde.

Figure 1

Ca/Mg-based classical chemical garden. The garden formed from a 0.25 g pellet of 1:1 CaCl₂/MgCl₂ submerged into a 1 M Na₂SiO₃ solutions that contained 100 mM Na₂CO₃.

Figure 2

Powder X-ray diffraction pattern for a Ca/Mg-Based chemical garden. The garden is comprised of microcrystalline B = brucite R040077, C = calcite R040170, A = aragonite R040078, M = magnesite R040114, and D = dolomite R040030. The garden is also comprised of amorphous calcium and magnesium, carbonates, hydroxides, and silica. Base line calibrated with Crystal Sleuth software.

Figure 3

Time-Point Experiment. Samples extracted from ongoing reactions at 25 min, then placed on ice. (a) Reaction with no minerals or chemical gardens, only Cannizzaro products found. (b) Formose reaction with Ca and Mg CO₃ powder. (c) Formose reaction with Ca/Mg-Silica Garden. (d) Formose reaction with olivine. (e) Formose reaction with serpentinite. (f) Formose reaction with magnetite, only Cannizaro products found. These samples were analyzed using NMR with water suppression, peaks at 1.3 and 4.1 ppm represent lactic acid, 1.9 ppm indicates acetic acid, 8.4 ppm formic acid, 3.9 ppm represents glycolic acid, and 3.2 ppm represents methanol.

Scheme 2

A Mechanism for the First step of the Formose Reaction with a Catalyst Present.

Figure 4

Powder X-ray diffraction pattern for a Ca/Mg-Based chemical garden (top) before being exposed to the formose reaction. Powder X-ray diffraction pattern for a Ca/Mg-Based chemical garden (bottom) after being exposed to the formose reaction. The garden is comprised of microcrystalline B = brucite, C = calcite, A = aragonite, M = magnesite, and D = dolomite. The garden is also comprised of amorphous calcium and magnesium, carbonates, hydroxides, and silica. Base line calibrated with Crystal Sleuth software.