Hydrothermal Evolution Of Small Organic Molecules Before The Origin Of Life

The origin of life has long been regarded as one of the most challenging and compelling scientific problems. The emergence of life can be traced to billions of years ago, it is impossible to directly observe the processes of origin of life, and the environment of early earth remains uncertain. The only way to speculate the environment of the early earth and origin of life depends on the research of geology and experimental simulation. The origin of life is also a highly interdisciplinary research area, solving this problem not only requires chemistry research but also biology, physics, astronomy, earth and planetary science and other disciplinary fields. Although the challenge of the origin of life is hard to surmount, human beings have never quitted on the exploration of the origin of life. This study not only satisfies people's curious of prehistoric environment and the origin of life, but also help us to understand and clarify the essence of life, to master the law of development of life. It will also promote the progress of science and technology, and let us plan the future of humanity correctly.There are many kinds of theories about the origin of life, but it is generally believed that life on the earth evolved from inorganic small molecules. In chemical evolution theory, submarine hydrothermal environments are favored as the most likely site for the origin of life. Deep-sea hydrothermal vents are similar with geological terrain of the early earth, and have greatly range of temperatures and p H, which provide enough materials and energy for the origin of life. Scientists have conducted many researches on chemical evolution under hydrothermal condition to reveal process of origin of life on the early earth.In this paper, we investigated the evolution of small biological molecules before origin of life by simulating the reaction of small organic molecules under hydrothermal environment. We studied the reaction of ethanol in alkaline hydrothermal environment, achieved the abiotic synthesis of long-chain alcohols which confirms the feasibility of synthesis of long-chain alcohols under hydrothermal conditions. We also studied the synthesis of glycine, alanine and its derivative N-acetyl alanine under different hydrothermal environments, which offered a new clue for the emergence of amino acids in hydrothermal vents before origin of life.1. We successfully realized the transform of ethanol to long-chain alcohols by simulating the alkaline hydrothermal vents environments. The long-chain alcohols may be the precursors of long-chain acid and phospholipid, which were the basic materials for the synthesis of cell membranes. For the first time, we introduced the Guerbet reaction into the study of origin of life. The ethanol can be transformed to 1-butanol, 2-ethyl butanol, 1-hexanol, 2-ethyl hexanol and n-octyl alcohol in alkaline hydrothermal environments with the metal powders as catalysts. We found the cobalt powder show the best catalytic effect for the reaction, and no change was found on the cobalt powder after the catalytic reaction. Then we study the reaction mechanism and found that the reaction from ethanol to long-chain alcohols probably via three pathways including dehydrogenation, aldol condensation, and hydrogenation. Since there was no loss of hydrogen, the productions were saturated alcohols, which continued to synthesis more longer alcohols. Our study provided a new route for the synthesis of long-chain alcohols in hydrothermal vents before origin of life. Comparing to Fischer-tropsch synthesis reaction in liquid phase, the reaction was more effective and realizable. The reaction might play an irreplaceable effect on the synthesis of long-chain alcohols in the alkaline hydrothermal vent environments.2. We study the synthesis of glycine from ethanolamine under alkaline hydrothermal conditions by utilizing an inflatable autoclave, we ruled out the possibility of oxidation reaction by oxygen. We also found metal powders had a good catalytic effect on glycine synthesis, the highest yield of glycine was 7.9%. some kinds of metal oxides also had catalytic effect. This greatly enhanced the possibility of synthesis of glycine from ethanolamine. Then we studied the reaction mechanism. The synthesis of glycine from ethanolamine mainly through two steps, the reaction started from the oxidation ethanolamine to form 2-aminoacetaldehyde over the catalyst by dehydrogenation and followed by a Cannizzaro Reaction to give glycine in alkaline condition. The high temperature and high pressure were conducive to ethanolamine evolution to glycine, when the reaction conditions in the range of 80-160 oC and 0.1-8MPa,.the yield of glycine increased with the increase of reaction temperature and pressure The reaction from ethanolamine provide a new method for the synthesis of glycine under hydrothermal environments.3. We studied the influence of different hydrothermal conditions for pyruvate acid evolution to N-acetylalanine and alanine. The synthesis of N-acetylalanine from pyruvate and different nitrogen source in strong acid hydrothermal conditions was easily achieved. It became difficult for the reaction when p H is greater than 3. Then we found the reaction can occur at 30 oC, and 70 oC was the best temperature for the reaction. At last, we studied the stability of N-acetylalanine under hydrothermal conditions, and find that the product of alanine in the solution maybe the result of hydrolysis of N-acetylalanine. The experiment enhances the pathway for the hydrothermal synthesis of biomolecules from pyruvic acid before origin of life, and found a new reaction route for the synthesis of alanine and N-acetylalanine.In summary, the origin of life is a globally concerned scientific issue. We have made considerable progress to surmount this problem, but the origin of life is not completely solved, much more works are needed to explore the origin of life. The thesis mainly studies the hydrothermal evolution of organic molecules before the origin of life and provides new ideas for the prebiotic synthesis of long-chain alcohols and amino acids, strengthens the theoretical basis of hydrothermal origin of life.