Life, as we know it, has emerged from the association of simple building blocks (e.g. HCN, NH3, aldehydes, etc). The reactions required to form the complex subunits of life face a great entropic barrier due to the intermolecular nature of their reactivity. Intermolecular reactions are slow at low concentrations, and therefore, the assembly of complex subunits requires the presence of a concentration mechanism. Formaldehyde, which was present in concentrations as high as 0.02 M, may have been used as a concentration mechanism on early Earth. By tethering two molecules together, formaldehyde allows catalysis via temporary intramolecularity. Moreover, formaldehyde has been shown to act as a hydrolase / hydratase mimic, allowing important rate accelerations in hydration and hydrolysis reactions which are of fundamental importance to prebiotic chemistry. Herein, the efficiency of formaldehyde as a catalyst, operating via temporary intramolecularity is demonstrated for a hydroamination reaction that occurs in dilute aqueous conditions. First, using soluble N-methylallylamine and Nmethylhydroxylamine, formaldehyde allowed catalytic turnover at prebiotically relevant formaldehyde concentrations (0.02 M) for a model hydroamination reaction. The efficiency of formaldehyde was compared to other prebiotic aldehydes, demonstrating that although other prebiotic aldehydes are capable of inducing temporary intramolecularity, they were inferior.A second small molecule which may have played a role in the origin of life is D-glyceraldehyde. Since life’s molecules are homochiral, there is a need to explain how this homochirality arose. There have been many breakthroughs by the scientific community when it comes to addressing this challenge, however there is still no general consensus on the origins of homochirality from a prebiotic perspective. Herein, we demonstrate that D-glyceraldehyde is capable of templating a challenging intermolecular reaction while also transmitting some of its chirality to the product. Though the enantiomeric excess produced was generally low (usually around 20 %), there is a significance behind these results due to prebiotically relevant amplification procedures. Lastly, formaldehyde is examined as a possible desymmetrizing agent; coupled with Brønsted acids, the possibility of formaldehyde to induce desymmetrization of alpha-amino or alpha-hydroxy diesters to produce azlactones, and oxalactones, respectively will be established. Moreover, the use of a chiral Brønsted acid would introduce the ability to achieve this transformation in an enantioselective manner. The resulting azlactones / oxalactones are valuable for two reasons: 1) the lactones are present in bioactive molecules, and 2) the lactones can be hydrolyzed to produce chiral alpha-amino / alpha-hydroxy acids. Therefore, we began a systematic study of the conditions required to allow this transformation to occur. This study indicates that the desymmetrization of an alpha-amino diester is possible, producing moderate yields of the resulting azlactone. The desymmetrization of alpha-hydroxy diesters however proved more challenging, and no conversion was observed. Further investigation is required to the increase efficiency of the desymmetrizations, and experimentation with chiral Brønsted acids is required in order to discover enantioselective transformations.

Since late 1990s, organocatalysis has been widely explored in many aspects and achieved various difficult transformations. In this field, carbonyl catalysis, which could be traced back to 1860 has been developed with impressive progress including asymmetric variants. Over the years, major activation modes were developed for carbonyl catalysis including exploiting temporary intramolecularity to form catalytic tethers and transient intramolecular nucleophiles, dioxirane formation and imine formation. On the other hand, electrophilic activation is also an important area of organocatalysis where impressive progress has been achieved. However, limited examples were reported to achieve the electrophilic activation via carbonyl catalysis. Organophosphorus compounds are crucially important in many aspects in organic chemistry. Many approaches were developed for asymmetric organophosphorus compounds. In this work, different types of organophosphorus compounds were used as the substances for aldehyde-catalyzed hydrolysis reactions. The first part of this thesis illustrated the strategy to combine carbonyl catalysis and electrophilic activation. The hydrolysis of organophosphorus compounds containing P(=O)-N bond were investigated based on Jencks and Gilchrist’s preliminary results with formaldehyde as the catalyst to promote the hydrolysis of one inorganic substance, phosphoramidate. This Chapter describes a systematic research to identify a superior catalyst, o-phthalaldehyde, and develop catalytic hydrolyses of various organophosphorus compounds containing P(=O)-NHR subunits. Gratifyingly, the reaction proved efficient with phosphinic amides and phosphoramidates. Moreover, chemoselectivity was also studied and selective hydrolysis of the P(=O)-N bonds in the presence of P(=O)-OR bonds could be accomplished. The second part of this thesis demonstrated the further development of one of the major modes of carbonyl catalysis. Formaldehyde was identified as the efficient catalyst to react with α-amino phosphonates to form the transient intramolecular nucleophile, which facilitated the subsequent hydrolysis reactions. In this Chapter, different primary and secondary α-amino phosphonates with phenol as the leaving group, were tested in the reaction conditions. As a result, a vast of mono esters of α-amino phosphoric acids could be formed as the products. Finally, the last portion of this thesis applied the methodologies developed in Chapter 2 to prebiotic chemistry. A prebiotic-related aldehyde, glycolaldehyde was studied as the catalyst for the hydrolysis of organophosphorus compounds containing P(=O)-N bond, including phosphinic amides and phosphoramidates. Additionally, other prebiotic important substances, diamidophosphate (DAP) and monoamidophosphate (MAP) were also investigated for potential glycolaldehyde-catalyzed phosphorylation reaction under aqueous conditions. In the presence of catalytic amount of glycolaldehyde, 1) when water was used as the nucleophile, the hydrolysis of DAP and MAP were significantly improved; 2) when other phosphate nucleophiles were added to compete with water, DAP could act as a phosphorylating reagent to phosphorylate other phosphate nucleophiles. Overall, the results presented in this thesis investigated two different activation modes, electrophilic activation and transient intramolecular nucleophiles, for carbonyl catalysis to hydrolyze different organophosphorus compounds, phosphinic amides, phosphoramidates and α-amino phosphonates. The application of carbonyl catalysis to prebiotic chemistry was also achieved especially with the phosphorylation reaction with DAP.

We present here the hypothesis of a possible relationship between metal atom clusters and the formation of organic molecules in the interstellar medium and on small bodies as a possible pathway to the origin of such molecules. Two distinct stages are díscussed: a) the possible formation and presence of atom clusters in space and on the primitive Earth, and b) the synthesis of interstellar and terrestrial prebiotic organic molecules, a process in which metalclusters could be the active catalysts. The confirmatíon of these suggestions might be very important in arder to explain the presence of extra-terrestrial organic molecules in the interstellar medium, small bodies and planetary systems, and therefore would have great relevance in cosmochemistry and in the current theories about the origins of life.

abstract: The origin of Life on Earth is the greatest unsolved mystery in the history of science. In spite of progress in almost every scientific endeavor, we still have no clear theory, model, or framework to understand the processes that led to the emergence of life on Earth. Understanding such a processes would provide key insights into astrobiology, planetary science, geochemistry, evolutionary biology, physics, and philosophy. To date, most research on the origin of life has focused on characterizing and synthesizing the molecular building blocks of living systems. This bottom-up approach assumes that living systems are characterized by their component parts, however many of the essential features of life are system level properties which only manifest in the collective behavior of many components. In order to make progress towards solving the origin of life new modeling techniques are needed. In this dissertation I review historical approaches to modeling the origin of life. I proceed to elaborate on new approaches to understanding biology that are derived from statistical physics and prioritize the collective properties of living systems rather than the component parts. In order to study these collective properties of living systems, I develop computational models of chemical systems. Using these computational models I characterize several system level processes which have important implications for understanding the origin of life on Earth. First, I investigate a model of molecular replicators and demonstrate the existence of a phase transition which occurs dynamically in replicating systems. I characterize the properties of the phase transition and argue that living systems can be understood as a non-equilibrium state of matter with unique dynamical properties. Then I develop a model of molecular assembly based on a ribonucleic acid (RNA) system, which has been characterized in laboratory experiments. Using this model I demonstrate how the energetic properties of hydrogen bonding dictate the population level dynamics of that RNA system. Finally I return to a model of replication in which replicators are strongly coupled to their environment. I demonstrate that this dynamic coupling results in qualitatively different evolutionary dynamics than those expected in static environments. A key difference is that when environmental coupling is included, evolutionary processes do not select a single replicating species but rather a dynamically stable community which consists of many species. Finally, I conclude with a discussion of how these computational models can inform future research on the origins of life. / Dissertation/Thesis / Doctoral Dissertation Physics 2018

Dans le contexte prébiotique du " monde ARN ", les ribonucléotides sont considérés comme étant les premières espèces à avoir émergé sur Terre. En milieu aqueux, leur formation est défavorable thermodynamiquement. Les voies de synthèse de nucléotides décrites en phase homogène impliquent l'utilisation des molécules activées. En 1951, Bernal a introduit une autre voie de synthèse impliquant des surfaces minérales. Cependant, dans cette voie, les effets thermodynamique et/ou catalytique des surfaces minérales restent inexplorés. Dans le cadre de l'hypothèse de Bernal, notre travail présente pour la première fois une étude in-situ de la réactivité thermique des " briques élémentaires " des nucléotides adsorbés sur des surfaces minérales avec comme objectif de réaliser la synthèse des nucléotides sans activation chimique. Ce travail a montré dans un premier temps que les surfaces minérales sont capables de déclencher la formation de polyphosphates inorganiques à partir de monophosphates à des températures modérées. D'autre part, l'adsorption du ribose sur la surface de la silice a permis d'améliorer sa stabilisation thermique : alors qu'il est instable dès 90°C en milieux aqueux, il devient stable jusqu'à 200°C après adsorption sur la silice. Dans un deuxième temps, nous avons mis en évidence la formation de PRPP, un intermédiaire réactionnel très important, par co-adsorption du ribose avec du phosphate inorganique sur la surface de la silice. Enfin, on a pu montrer la glycosylation de l'adénine et la formation après co-adsorption de ses composants sur les deux surfaces minérales utilisées. Une étude préliminaire suggère même la possibilité de dimérisation des nucléotides. / In the « RNA world» prebiotic scenario, ribonucleotide polymers are considered as the first biochemical species to have emerged. However, in aqueous solution, their formation through conventional mechanisms of condensation is thermodynamically forbidden. Several synthesis pathways of nucleotides have been described in aqueous solution; most often, they involve chemically activated molecules. Another pathway to nucleotides implies mineral surfaces, which have been considered in prebiotic processes at least since the work of Bernal in 1951. However, these studies have hardly tried to understand surface-molecule interactions and consequently, thermodynamic and/or catalytic effects of mineral surfaces are not well rationalized. In the context of Bernal's hypothesis, we present for the first time an in-situ study of the thermal reactivity of nucleotides “building blocks” adsorbed on mineral surfaces (amorphous silica, saponite) emphasizing the synthesis of nucleotides without chemical activation. In our work, we first show that mineral surfaces are able to trigger the formation of inorganic polyphosphates from monophosphates at moderate temperatures. On the other hand, adsorption of ribose on silica surface improves its thermal stabilization. While ribose decomposes at 90°C in aqueous solutions, it is stable up to 200°C on silica (in the presence of ZnCl2). Secondly, we have demonstrated the formation of PRPP, as important reaction intermediate, by co-adsorption of ribose and inorganic phosphate on the silica surface. Finally, we showed the glycosylation of adenine to adenosine and the formation of AMP (i.e. simultaneous glycosylation and phosphorylation) after co-adsorption of their components on both mineral surfaces employed. A preliminary study even suggests that nucleotide dimerisation can occur in the same conditions.

The Sutherland group recently demonstrated that from a mixture of oligoribonucleotide-2'- or 3'-phosphates the latter is chemoselectively acetylated. This is shown to mediate a template-directed ligation to give predominantly 3',5'-linked RNA that is acetylated at the ligation junction (acetyl-RNA). It was suggested that RNA emerged prebiotically via acetyl-RNA and also is proposed to have favourable genotypic properties due to greater propensity to form duplex structure. To study the properties of acetyl-RNA, their synthesis by solid-phase chemistry was required and described is the design of a 2'/3'-O-acetyl orthogonal protecting group strategy. Key to the orthogonal protecting group strategy is the use of (2-cyanoethoxy)carbonyl for the protection of the nucleobase exocyclic amines and a photolabile solid-phase linker group that allowed partial on-column deprotection. The synthesis of the 2'/3'-O-acetyl and 2'/3'-O-TBDMS phosphoramidites, in addition to preparation of a photolabile solid-phase support, are described. With the materials to hand the procedures for an automated synthesis of acetyl-RNA were optimised and several acetyl-RNA oligonucleotides were synthesised. The duplex stability of acetyl-RNA with up to four sites of 2'-O-acetylation were assessed by UV melting curve analysis. Remarkably, the acetyl groups caused a consistent decrease in Tm of between 3.0-3.2 °C. Thermodynamic parameters indicated a decrease in duplex stability that was consistent with a decrease in hydration of the minor groove resulting in a reduction of the stabilising hydrogen bonding network. The stability of a tetraloop was also found to decrease on acetylation. The acetylated- tetraloop it is able to form duplex at lower concentrations than the natural tetraloop. Additionally, it is more stable at high concentrations, indicating that acetyl-RNA favours duplex over other secondary structure. These properties are considered to give acetyl-RNA competitive advantage for their non-enzymatic replication. Aminoacylation of RNA is an important process in modern biology but the intermediacy of aminoacyl-adenylates is considered to be prebiotically implausible. A potentially prebiotic aminoacylation of nucleoside-3'-phosphates, selective for the 2'-hydroxyl, is presented. However, it was thought the aminoacylation yields could be improved and so a search for an alternative activator was conducted. Oligoribonucleotide-3'-phosphates were exposed to the aminoacylation conditions and selective aminoacylation at only the 2'-hydroxyl of the 3'-end was observed. In particular, the aminoacylation of a trimer lends support to Sutherland’s theory of a linked origin of RNA and coded peptide synthesis.

Titan, la plus grosse lune de Saturne, est l'un des objets planétaires clé dans le domaine de l'exobiologie. Son atmosphère dense et riche en diazote est le siège d'une chimie organique intense. Ce travail de thèse se concentre sur les aérosols organiques produits dans son atmosphère. Ces derniers jouent un rôle essentiel dans l'évolution de l'atmosphère et de la surface du satellite mais aussi dans sa chimie organique d'intérêt exobiologique. Dans un premier temps, afin de disposer d'analogues de laboratoires (« tholins ») fiables de ces aérosols, un dispositif permettant d'obtenir des tholins propres a été développé, testé puis optimisé. Puis, deux aspects complémentaires des aérosols de Titan ont été étudiés :- Leurs propriétés optiques. En effet, la connaissance de ces dernières est indispensable, entre autres, pour l'analyse et l'interprétation des données d'observations de Titan. Une étude détaillée et critique de l'ensemble des données disponibles relatives aux indices de réfraction a été menée. Elle a permis de mettre en évidence les lacunes à combler. En parallèle, des mesures expérimentale ont permis de déterminer la matrice de diffusion à plusieurs longueurs et pour une large gamme d'angles de diffusion. Les résultats obtenus montrent que les tholins ne présentent pas une forme en agrégats comme les aérosols de Titan bien que les données acquises semblent bien représenter les données d'observations de Titan.- Leurs possibilités d'évolution chimique une fois à la surface, en particulier, la possible interaction des aérosols avec un cryomagma d'eau-ammoniaque. Des modèles de formation de Titan ont permis de déterminer une composition en sel de l'océan interne et de la cryolave. A partir de cette composition originale, une étude expérimentale de diverses hydrolyses des tholins a été effectuée. Les résultats obtenus montrent la formation de nombreux composés organiques dont des molécules d'intérêts exobiologiques, parmi elles, des espèces identifiées seulement en présence de sels. De plus, une liste des précurseurs potentiels de ces composés a été établie ce qui pourrait constituer une base de donnée pour la recherche de la composition chimique des tholins et/ou aérosols de Titan / Titan, the largest moon of Saturn, is one of the key planetary objects in the exobiology field. Its dense, nitrogen-rich atmosphere is the site of intense organic chemistry. This PhD work focuses on the organic aerosols which are produced in Titan's atmosphere. They play an important role in atmospheric and surface processes but also in its organic chemistry of exobiology interest. At first, in order to produce reliable laboratory analogs (“tholins”) of these aerosols, a device for the synthesis of clean tholins has been developed, tested and optimized. Then two complementary aspects of Titan aerosols have been studied :- Their optical properties. Indeed, their knowledge is prime importance to analyze and to better interpret many of Titan's observational data. A detailed and critical review of all available data on refractive indices was conducted. The lacks in this field have been highlighted. In parallel, direct experimental measurements were used to determine the scattering matrix at two wavelengths and for a wide range of scattering angles. The obtained results show that the tholins do not have the shape of aggregates such as Titan aerosols although the acquired data seem to match with observational data.- Their potential chemical evolution at Titan surface, in particular, the possible interaction between aerosols and putative ammonia-water cryomagma. Modelings of Titan formation have recently permitted the characterization of a composition in salts of the subsurface ocean and the cryolave. From this new and original chemical composition, a laboratory study of several hydrolyses of tholins has been carried out. The obtained results show the formation of many organic compounds, among them, species identified only in the presence of salts. In addition, a list of potential precursors of these compounds has been established

The 'RNA World' hypothesis states that RNA was the first living system on the primitive Earth, where it carried out dual genotypic and phenotypic functions. Therefore, RNA must have self-assembled by purely chemical means from small prebiotic feedstock molecules. A plausible demonstration of the synthesis of RNA with the natural [5'→3'] phosphodiester linkage, and its self-replication has not been achieved so far. Some have speculated a 'simpler' informational polymer preceded it, and biology based on this polymer subsequently 'invented' RNA. The structurally simpler L-α-threofuranosyl nucleic acid (TNA) has been proposed as a primordial ancestor to RNA. A study into the potential self-assembly of TNA nucleotides was carried out. It is shown that as a direct result of TNA's structural simplicity, its generational chemistry is more difficult than RNA. The tetrose aminooxazolines are unstable under the conditions of its formation. The tetrose anhydronucleosides efficiently incorporate phosphate to form activated tetrose cytidine-2',3'-cyclic phosphates, but with the wrong stereochemistry. Strong support for the 'RNA world' hypothesis came from a report in 2009 of the prebiotic synthesis of activated pyridimine ribonucleoside-2',3'-cyclic phosphates. Oligomerisation studies were carried out on these activated monomers with various catalysts, and NMR studies were carried out to determine the aspects of their reactivity. It was found that only short oligomers are formed. However, nucleoside-2',3'-cyclic phosphates were found to selectively hydrolyse to a 2:1 mixture of 3' and 2'-monophosphates, and this observation was considered as etiologically relevant. Nucleoside-2' and 3'-monophosphates cyclise back to nucleoside-2',3'-cyclic phosphates upon phosphate activation, and so cannot be considered as direct candidates for oligomerisation. A chemistry that selectively uses the nucleoside-3'-phosphate for the synthesis of RNA, and recycles the unwanted 2'-phosphate would be highly desirable. Thus, a regio- and chemoselective reaction that selectively acetylates monomer and oligomer nucleoside-3'-phosphates at the 2'-hydroxyl in water is presented. Nucleoside-2'-phosphates are shown to acetylate less efficiently, and show a greater propensity to recyclise back to nucleoside-2',3'-cyclic phosphates. Purine nucleotides were also found to acetylate better than pyrimidines. This potentially primordial protecting group chemistry approach towards the prebiotic synthesis of RNA is conceptually novel, and has the potential to give a natural [5'→3'] phosphodiester linkage isomer. It is considered as a major step towards solving the long-standing problem of non-enzymatic self-replication of RNA.

Esta tese se insere no contexto da química prebiótica, que estuda a evolução química que ocorreu antes do surgimento da vida na Terra. Tal área pertence ao ramo de pesquisa da Astrobiologia, que estuda o surgimento, a evolução, distribuição e futuro da vida na Terra ou em outro lugar do Universo. Dentre as várias hipóteses abordadas na química prebiótica, a hipótese mineral é foco de estudo deste trabalho, ou seja, se os minerais podem ter agido como preconcentradores ou protetores de moléculas biologicamente relevantes para a química prebiótica e como catalisadores de reações. A classe mineral de hidróxidos duplo lamelares (HDL) é estudada inicialmente considerando se sua síntese seria possível em um ambiente prebiótico. Desta forma, o HDL foi sintetizado por dois métodos de síntese (coprecipitação e reconstrução) e em quatro composições distintas de água do mar sintética, que mimetizam diferentes fases geológicas da Terra, os resultados mostraram a formação deste mineral em todas as composições de água do mar analisadas. Posteriormente, o estudo da interação de biomoléculas com HDL foi feito visando caracterizar se estas poderiam estar inseridas no espaço interlamelar deste mineral. O íon tiocianato, precursor de biomoléculas, e as bases nitrogenadas adenina, timina, e uracila mostraram-se presentes nas amostras de HDL sintetizadas pelos dois métodos, coprecipitação e reconstrução. As amostras foram caracterizadas por difratometria de raios X, análise termogravimétrica, análise elementar e por espectroscopia vibracional, Raman e no infravermelho. Embora os resultados iniciais indiquem que as biomoléculas possam estar interagindo com o mineral por adsorção e não necessariamente estejam intercaladas, estudos com lavagem das amostras com carbonato de sódio mostraram a troca iônica das biomoléculas pelo ânion inorgânico e sugerem que estas encontravam-se realmente no espaço interlamelar do mineral. Foram feitas então simulações de ambientes extremos nos sistemas HDL + biomoléculas para avaliar se a presença do mineral aumenta a estabilidade das biomoléculas frente a aquecimento, radiação UVC e radiação ionizante já que tais condições extremas estariam presentes na Terra primitiva / This thesis subject is related to prebiotic chemistry, which studies the chemical evolution that happened before the origin of life on Earth. This subject belongs to the Astrobiology research area, which studies the origin, evolution, distribution and future of life on Earth and elsewhere in the Universe. Among the many hypothesis that prebiotic chemistry encompass, the mineral hypothesis is the aim of this thesis, that is, if minerals could have had a role in preconcentrating and protecting molecules relevant to prebiotic chemistry, and also if they could have acted as catalists. The layered double hydroxide (LDH) minerals are studied and the first question is if they could have been synthetized in a prebiotic environment. Four different seawater compositions are analyzed, considering many geological periods of Earth, and two synthesis methods were studied: coprecipitation and reconstruction. The results showed that the LDHs are formed in all seawater types studied. Following these studies, we discuss whether biomolecules could be in the interlayer space of this mineral. Thiocyanate, a biomolecule precursor, and the nucleic acids adenine, thymine and uracil were present in the LDH samples synthetized either by coprecipitation and reconstruction, and they were characterized by X-Ray diffraction, thermogravimetric analysis, elemental analysis and by vibrational spectroscopy: IR and Raman. Although the preliminary results showed that the biomolecules are not necessarily intercalated, but may simply be adsorbed on the minerals, after washing with a sodium carbonate solution, the biomolecules were replaced by the inorganic anion, suggesting that the former was in fact intercalated in the mineral. Extreme conditions simulations were then performed on the LDH plus biomolecules systems to evaluate whether the mineral may act as a protector and stabilize the biomolecules when these were heated or irradiated with UV-C and ionizing radiation, since such scenarios would be common on early Earth

Desde o clássico experimento de Miller em 1953 evidenciando a formação de aminoácidos em condições de Terra primitiva, a química do período pré-biótico ainda é muito discutida. Cita-se, por exemplo, o papel da teoria sulfociânica, que descreve a origem de moléculas orgânicas a partir de compostos contendo enxofre, como o tiocianato de amônio (NH4SCN). Neste contexto, essa Tese aborda um estudo sobre a investigação do NH4SCN em condições pré-bióticas. Para isso, experimentos de oxidação eletroquímica e de irradiação ultravioleta (UV) em amostras contendo NH4SCN em diferentes condições experimentais foram conduzidos. Por eletroquímica acoplada à espectroscopia vibracional no infravermelho (FTIR in situ), identificou-se como o primeiro produto da oxidação do NH4SCN, o dímero tiocianogênio (SCN)2, que é um reconhecido precursor dos oligômeros do período pré-biótico. Em contrapartida, a irradiação UV do NH4SCN levou a formação de enxofre ortorrômbico (S8) e das bases nitrogenadas 4-(3H)-pirimidinona, citosina, purina e adenina, além de outras moléculas. Provavelmente, o cianeto de hidrogênio (HCN) é um dos precursores das biomoléculas supracitadas, contrariando uma possível rota via (SCN)2. Os resultados desse estudo também reforçam a hipótese de que não há formação direta de aminoácidos por irradiação do NH4SCN. Desta forma, propõe-se aqui que a formação dos blocos do DNA, as bases nitrogenadas, também possa ser inserida no contexto da teoria sulfociânica. / Since the classic Miller experiment in 1953 evidencing the amino acids formation under early Earth conditions, the chemistry of the prebiotic period is still very discussed. It is cited, for example, the role of sulfocyanic theory, which describes the origin of organic molecules from sulfur-containing compounds such as ammonium thiocyanate (NH4SCN). In this context, this thesis shows a study about the investigation of NH4SCN in prebiotic conditions. Thereby, experiments of electrochemical oxidation and ultraviolet (UV) irradiation were carried out with samples containing NH4SCN in different experimental conditions. By using electrochemistry coupled to Fourier transform infrared spectroscopy (FTIR in situ), the dimer thiocyanogen (SCN)2 was identified as the first oxidation product of NH4SCN, which is a recognized precursor of the oligomers from prebiotic period. In counterpart, UV irradiation of the NH4SCN led to the formation of orthorhombic sulfur (S8) and the nitrogenous bases 4-(3H)-pyrimidinone, cytosine, adenine and purine, besides other molecules. Probably, hydrogen cyanide (HCN) is one of the precursors of the biomolecules abovementioned, contradicting a possible route via (SCN)2. The results of this study also reinforce the hypothesis that there is no direct formation of amino acids by irradiation of NH4SCN. Thus, it is proposed here that the formation of DNA blocks, the nitrogenous bases, can also be inserted in the context of sulfocyanic theory.