Marine deoxygenated areas are expanding, and more hypoxic zones emerge globally. Climate change induced warming and stratification can extrapolate the biological oxygen demand, more predominantly at coastal areas and reefs with dense vegetation and high metabolic activity. The diurnal oxygen fluctuation can reach a critically low oxygen level at nighttime, exposing aquatic organisms to severe hypoxia that could interfere with viable ecosystem functions. Little is known about the impact of hypoxia on marine primary producers macroalgae, mainly the physiological adaptation of the Red Sea macroalgae under climate change scenarios is understudied. Here we investigate hypoxia thresholds at night time for conspicuous Red Sea macroalgae species calcareous Halimeda opuntia and Padina boryana and noncalcifying brown algae Sargassum latifolium. We utilized a computer-based gas system to expose the samples to different oxygen treatments (normoxia, hypoxia, and severe hypoxia) that mimic in situ water chemistry at 32 °C. We monitored algal physiological response during 12 hours of exposure to different oxygen levels in the dark by measuring photochemical efficiency, respiration rates, and cellular viability. For the duration of our experiments (12h), we did not detect lethal thresholds. In all tested species, severe hypoxia significantly decreased photochemical efficiency, and hypoxia had a limited impact on photochemical efficiency. However, both low oxygen treatments significantly decreased respiration rates and induced changes in cellular activity. We concluded a sublethal O$_2$ thresholds SLC$_{(50)}$ of 1.2 ±0.1, 1.5 ±0.1, and 1.7 ±0.1 mg O$_2$ L$^{−1}$ ±SD for H. opuntia, P. boryana, and S. latifolium responses, respectively. We also found that during 12 hours of treatments, the median time to observe a 50% reduction in photochemical efficiency under severe hypoxia treatment relative to control was 6.3 ±1.4, 3.5 ±1.0, and 0.8 ±1.3 hours ±SD for H. opuntia, P. boryana, and S. latifolium responses, respectively. This study is the first assessment of Red Sea macroalgae response to hypoxia and the first dark nighttime algal adaptation of its kind for our proposed species. Further investigation is needed to assess daytime recovery, recurring dark hypoxia, and synergic or sequential effects of other environmental stressors on hypoxia thresholds.

Zeolite catalysts of three types (H-ZSM-5, Fe-ZSM-5 and H-Beta) were tested in the catalytic co-conversion of rapeseed cake and safflower oil into bio-fuel. This low pressure process was carried out at the temperatures of 350 and 400 °C. The yields and compositions of the product mixtures depended on the catalyst nature and the process temperatures. The produced organic phases consisted mainly of hydrocarbons, fatty acids and nitriles. This mixture possessed improved characteristics (e.g. heating value, water content, density, viscosity, pH) compared with the bio-oils, making possible its application as a bio-fuel. The most effective catalyst, providing the highest yield of organic liquid phase, was the highly acidic/wide-pore H-Beta zeolite. The products obtained on this catalyst demonstrated the highest degree of deoxygenation and the higher HHV (Higher Heating Value). The aqueous liquid phase contained water-soluble carboxylic acids, phenols and heterocyclic compounds.

This research studies the use of class=SpellE>titania (titanium dioxide, TiO2) as a catalyst for deoxygenation of class=SpellE>syngas derived oxygenates. These oxygenates are formed as byproducts when biomass derived syngas (CO & H2) is converted to ethanol on Rhodium or Molybdenum based catalysts. Conversion of these oxygenates to hydrocarbon would enhance the viability of class=SpellE>syngas to gasoline technology. This study revealed that class=SpellE>titania can indeed be used to convert syngas derived oxygenates to hydrocarbon at high temperature and pressure. Acetone condensation to mesitylene was studied very closely. The study revealed that the acid-base dual nature of class=SpellE>titania is key for the success of this reaction. When titaniawas combined with the zeolite H+/ZSM-5, a broad range of gasoline type hydrocarbon could be produced. Ethanol conversion to higher alcohols was studied as part of a partial deoxygenation of ethanol research. While this conversion was possible on class=GramE>titania, zirconia proved to be a better catalyst. Ethanol could be converted to 1-butanol and other higher alcohols at high temperature and pressure. The mechanism by which this occurs was studied as well.

<p dir="ltr">Borane-ammonia (BH₃-NH₃) has played an essential role in shaping and promoting the field of organic chemistry. However, we believe that the potential applications of BA in organic reductions have yet to be investigated. Our studies aimed to investigate BA as a reducing agent in organic reactions and to delve into the associated reduction mechanisms. In the second chapter of our research, we discovered that a combination of borane-ammonia and titanium tetrachloride (TiCl₄) has been explored as a versatile system for reducing various carbonyl compounds. By using BA with a small amount of TiCl₄ catalyst (10 mol%) in diethyl ether (Et₂O), we reduced different aryl and alkyl ketones into secondary alcohols at room temperature in just 30 minutes. This method is much faster than traditional uncatalyzed conditions, which usually take 24 hours or more to achieve the same reduction, and it does so without impacting other functional groups. Substituted cycloalkanones are selectively reduced to the thermodynamically favored product. Our deuterium labeling experiments found that the most probable pathway involves the hydroboration mechanism involving ketones and borane-ammonia in the presence of TiCl₄.</p><p><br></p><p dir="ltr">A slight variation in this chemical system can significantly impact the deoxyhalogenation process of aryl aldehydes, ketones, carboxylic acids, and esters. This process involves using a metal halide Lewis acid as a carbonyl activator, halogen carrier, and borane-ammonia. The selectivity of this process is determined by balancing the carbocation intermediate's stability with the Lewis acid's acidity. The choice of solvent and Lewis acid depends on the substituents present, and different substitution patterns have been explored. These principles have also been applied to selectively convert alcohols into alkyl halides. Furthermore, this system is used to selectively deoxygenate carbonyls of aldehydes and ketones into methyl and methylene hydrocarbons. The substituents on the benzene ring play a significant role in the deoxygenation process of carbonyl carbons in aldehydes and ketones.</p><p><br></p><p dir="ltr">In the third chapter of the study, various applications of the titanium system are examined. The TiCl₄/BH₃-NH₃ system was used to directly reduce a range of carboxylic acids to the corresponding alcohols at room temperature with good to excellent yields. This reduction method was achieved by adjusting the stoichiometry of borane-ammonia. This process is tolerant to various potentially reactive functional groups, such as N-protected amino acids, enabling the selective reduction of acids in the presence of amides and nitriles. Further, the titanium system was used to deoxygenation aromatic and aliphatic carboxylic esters into ethers. The ratio of borane-ammonia and catalyst controls the process. This method is the first practical borane-mediated process compatible with many sensitive functional groups and can convert challenging aromatic acid esters into ethers. Using BF₃–Et₂O as the catalyst changes the result products, reducing the esters to alcohols instead.</p><p><br></p><p dir="ltr">In the fourth chapter of our exploration, we looked at various applications of this system that involved reducing aliphatic and aromatic nitriles to primary amines. This was achieved by using 2.0 equivalents of <a href="" target="_blank">BH₃-NH₃ </a>and a molar equivalent of TiCl₄. We also found that the TiCl₄/BA system in dichloroethane (DCE) under reflux temperature efficiently reduces (deoxygenates) a range of aromatic and aliphatic primary, secondary, and tertiary carboxamides. We adjusted the catalyst and reductant stoichiometry accordingly, and the resulting amines were obtained in high yields using a simple acid-base workup.</p>

Cooperative oxygen binding by vertebrate tetrameric hemoglobins (Hbs) has been extensively studied and is relatively well understood. Nonetheless, Hill coefficients greater than four have been reported for adult avian, amphibian, and reptilian red blood cells. Such reports also exist for embryonic red cells from various animals. These results are controversial and not yet convincingly established. Oxygen binding studies on avian Hb D, which is known to undergo deoxygenation-dependent self-association, were carried out to answer this question. The goal was to determine unequivocally whether Hill coefficients greater than four occur. Such high Hill coefficients were observed but only at very high Hb D concentrations. Moreover, the early model of avian deoxy Hb D self-association was found to be incomplete. The model has now been expanded to describe better the observed sedimentation data at high Hb concentrations. The possibility that embryonic deoxy Hbs self-associate was also assessed by sedimentation studies of deoxygenated Hb solutions from a marsupial, the tammar wallaby. The results obtained show unambiguously that these embryonic Hbs self-associate upon deoxygenation. Recent phylogenetic analyses suggest that the avian [alpha superscript D]-globin originated from embryonic [alpha]-globins. This finding suggests that the propensity to self-associate upon deoxygenation is an intrinsic property of tetrameric Hbs with embryonic [alpha]-globins. Furthermore the residues mediating the inter-tetramer interactions in adult avian deoxy Hb D and embryonic deoxy Hbs are likely to be the same. Recombinant globins were expressed in bacteria and protocols for the assembly of avian recombinant tetrameric Hb D developed. Initial measurements by sedimentation were carried out to verify the role of a conserved glutamate residue previously speculated to be involved in inter-tetramer interactions. The present studies provide a framework for future investigations of deoxygenation-dependent Hb self-association. In particular the need to carry out oxygen equilibrium measurements at high Hb concentrations as well as sedimentation studies of the deoxygenated Hb solutions is stressed. / text

Project I: [Ru(OH2)3(4'-phenyl-2,2':6',2''-terpyridine)](OTf)2 as a Homogeneous Hydrogenation Catalyst for Biomass Derived Substrates. The complex [Ru(OH2)3(4'-phenyl-2,2':6',2''-terpyridine)](OTf)2 has been shown to be an active ionic hydrogenation catalyst for selected carbonyls, diols and glycerol by the Schlaf group. It was postulated to also be active for other biomass derived substrates such as levulinic acid (LA), furfural and 5-hydroxymethyl furfural (HMF). Synthesis of the complex was optimized and full characterization carried out by 1H/13C –NMR. The complex was tested against LA in aqueous sulfolane medium and the furfural/HMF model system 2,5-hexanedione in water. Activity of the complex was compared to the analogous metal-ligand bifunctional (MLB) system described in Project II. The complex exhibited good thermal stability up to 200 oC in 90/10 wt% sulfolane/water mixtures and was capable of hydrogenation of LA to γ-valerolactone in 95% yield. Addition of protic acids to the reaction mixture and increasing proportions of water decreased the activity of the complex towards the hydrogenation of LA. Project II: [Ru(OH2)3(di(picolyl)amine)](OTf)2 as an acid-, water- stable, metal-ligand bifunctional deoxygenation catalyst. The complex [Ru(OH2)3(di(picolyl)amine)](OTf)2 was postulated to be an active MLB ionic hydrogenation catalyst under acidic aqueous conditions. Using the substantially labile [Ru(DMF)6](OTF)3 ruthenium complex as the precursor, the desired complex was prepared insitu by coordination of the DPA ligand and concomitant reduction of Ru3+ to Ru2+. The complex was characterized by 1H/13C-NMR and tested for the hydrogenation of LA, 2,5-hexanedione, furfural and HMF under acidic aqueous conditions. The complex exhibited thermal stability up to 150 oC and was active for the hydrogenation of carbonyls, as demonstrated by the conversion of 2,5-hexanedione to 2,5-hexanediol in 94% yield in water. Addition of H3PO4 as an acid cocatalyst resulted in nearly complete conversion to dimethyltetrahydrofuran (DMTHF) but further deoxygenation could not be achieved. Direct comparision of [Ru(OH2)3(di(picolyl)amine)](OTf)2 and [Ru(OH2)3(4'-phenyl-2,2':6',2''-terpyridine)](OTf)2 under identical conditions against LA and 2,5-hexanedione demonstrated that the[Ru(OH2)3(di(picolyl)amine)](OTf)2 catalyst is more active than the [Ru(OH2)3(4'-phenyl-2,2':6',2''-terpyridine)](OTf)2 complex in all cases, suggesting that the di(picolyl)amine complex operates through a MLB ionic hydrogenation mechanism. / NSERC

This dissertation presents the experimental determination of the two most important coefficients in modeling of dissolved oxygen in water bodies: the reaeration-rate coefficient K2 and the deoxygenation coefficient K1. The deoxygenation coefficient was determined in three representative sections of the considered basin: the first with urban characteristics, the second mixed and the third rural characteristics. Three experiments were conducted, featuring different flows in the Vacacaí Mirim River. K1 was determined by constructing the oxygen depletion versus time curve, in a 20 days period. K1 ranged from 0.15 day-1 to 0.27 day-1. An increase in K1 value was observed due to flow increment, in mixed and rural characteristics areas, reflecting the major contribution of diffuse organic load in those areas. It was not possible to observe a significant variation of flow in the urban feature section, due to damping of the flow by the upstream reservoir. This section is considered to present a decrease in the K1 value as liquid discharge increases, since it is noticeable the sewage contribution. The reaeration-rate coefficient was determined using inert tracer technique, applying propane as gas tracer and Rhodamine WT as dye tracer. Two experiments were conducted in two reaches, both in the highest urbanization areas of the Vacacaí Mirim basin. In the first experiment, K2 value was 30.30 day-1 for the first reach, and 24.77 day-1 for the second. In the second test, K2 obtained was 14.91 day-1 and 12.73 day-1, respectively. An approach was made about alternative methods for experimental determination of the reaeration-rate coefficient and the predictive equations of K2. The results obtained in tests were compared with those predicted by the most important equations in literature. The predictive equations presented large discrepancy between them, and the latest formulas, derived from K2 measurements obtained by the gas tracer methods, presented the lowest variation, ranging from -32.95% to 14.51%. Based on results, an equation was proposed to estimate K2 restricted to the studied sites, adapting from the equations of Melching and Flores. / Esta dissertação apresenta a determinação experimental dos dois coeficientes mais importantes na modelagem do oxigênio dissolvido em corpos d‟água: o coeficiente de reaeração superficial K2, e o coeficiente de desoxigenação K1. O coeficiente de desoxigenação foi determinado em três seções representativas da bacia em estudo, sendo uma com característica urbana, uma mista e uma rural. Três experimentos foram conduzidos, caracterizando diferentes vazões no rio Vacacaí Mirim. O coeficiente K1 foi determinado por meio da construção da curva de decaimento de oxigênio versus tempo, num período total de 20 dias. Os valores de K1 variaram de 0,15 dia-1 a 0,27 dia-1. Observou-se um aumento de K1 com o aumento da vazão, nas seções de característica mista e rural, evidenciando a maior contribuição da carga orgânica de maneira difusa nessas áreas. Não foi possível observar uma variação de vazão significativa na seção de característica urbana, devido ao amortecimento do escoamento pelo reservatório situado a montante da seção. Nesta seção, possivelmente, um aumento na descarga líquida acarreta uma diminuição no valor do coeficiente de desoxigenação, já que é visível a contribuição pontual de esgoto doméstico. O coeficiente de reaeração superficial foi determinado utilizando a metodologia dos traçadores inertes, com o emprego de propano como traçador gasoso e Rodamina WT como traçador de referência. Dois experimentos foram conduzidos em dois trechos, na região de maior urbanização da bacia hidrográfica do rio Vacacaí Mirim. No primeiro experimento, o valor de K2 foi de 30,30 dia-1, para o primeiro trecho, e 24,77 dia-1, para o segundo. No segundo ensaio, o K2 obtido foi de 14,91 dia-1 e 12,73 dia-1, respectivamente. Aborda-se a respeito de outras metodologias de determinação experimental do coeficiente de reaeração, bem como sobre as equações de estimativa de K2. O valor obtido nos ensaios foi comparado com aqueles previstos pelas principais equações presentes na literatura. O valor estimado pelas equações apresentou grande discrepância entre as mesmas, sendo que as equações mais recentes, propostas a partir da regressão de dados de K2 obtidos pela própria metodologia dos traçadores inertes, apresentaram as menores variações, entre -32,95% e 14,51%. Baseado nos resultados propôs-se uma equação para estimativa de K2 exclusiva para os trechos estudados, adaptada a partir das equações de Melching e Flores.

This thesis is centred around sequential C-C bond forming processes using oxygenated electrophiles. A major part of this research focuses on the constructive deoxygenation of 2-methoxyphenol (guaiacol), a major breakdown product of the renewable feedstock, lignin. 1,2-dielectrophiles are known to be challenging substrates for catalysis if both leaving groups are of similar reactivity, however high selectivity was observed in the palladium- catalysed Grignard cross-coupling of 2-methoxyphenyl-1H-imidazole-1-sulfonate. The previously untested Grignard cross-coupling catalyst, [PdCl₂(Xylyl-Phanephos)], was found to be highly active. A 2-benzoxazolyl functionality was shown to be an excellent directing group for the chelation-controlled nucleophilic aromatic substitution of aryl methyl ethers. However, this modified Meyers reaction is limited to aryl ethers containing an ortho-chelating group. To expand the ether scope, nickel-catalysed Grignard cross-coupling was studied. [NiCl₂(PⁿBu₃)2] showed increased activity in the Grignard cross-coupling of challenging ortho-substituted anisoles compared to the well-renowned [NiCl₂(PCy₃)2] and several Ni0 -NHC systems, with a ligand steric effect demonstrated. The success of [NiCl₂(PⁿBu₃)2] was extended to more activated methoxynaphthalene substrates, in which the lowest reported catalyst loadings (0.1-0.25 mol%) were reported. Induction periods at 0.1 mol% suggested the requirement of inorganic Lewis-acidic magnesium salts to be formed in situ before any considerable activity was observed. Further work is required to increase reaction and ether scope, but this work provides a basis for exploiting lignin- derived phenols as a framework in the synthesis of functionalised chemicals of higher value. The final results chapter concerns an alternative sequential C-C bond forming process using another oxygenated electrophile. [PdCl₂((S)-Xylyl-Phanephos)] was used to accomplish a Grignard cross-coupling of vinyl tosylate, with the product then subjected to a highly enantioselective methoxycarbonylation using the same catalyst. This lead to a concise synthesis of (S)-Flurbiprofen.

La pyrolyse flash est un procédé attrayant pour convertir la biomasse lignocellulosique en bio-huiles, intermédiaires énergétiques potentiellement valorisables en biocarburants et/ou intermédiaires chimiques. L’émergence d’une telle filière requiert la mise au point d’une stratégie catalytique efficace et innovante qui permette de diminuer la teneur en oxygène des bio-huiles. Les mécanismes de pyrolyse ont lieu à la fois au sein de la biomasse - mécanismes primaires - et en phase gazeuse - mécanismes secondaires-. Par conséquent, notre démarche a consisté à tester si l’imprégnation d’un précurseur catalytique dans la biomasse permet d’agir sur les mécanismes primaires afin de favoriser la désoxygénation. Puis, nous avons cherché à favoriser le craquage catalytique des vapeurs de pyrolyse en utilisant un catalyseur hétérogène.Nos travaux montrent que la pyrolyse de biomasse imprégnée avec des sels de nitrates - Mn, Fe, Co, Ni, Cu, Zn et Ce - favorise principalement la dépolymérisation de la cellulose aux dépens de sa fragmentation. En outre, la présence d’anions nitrate catalyse la formation d’anhydrosaccharides déshydratés, employés pour synthétiser des molécules complexes. Après pyrolyse, un support carboné contenant des nanoparticules métalliques est obtenu et peut être valorisé pour catalyser la désoxygénation de molécules modèles en phase vapeur. Néanmoins, l’activité catalytique de ces charbons est limitée par leur faible surface spécifique, comme le montre la comparaison avec un charbon actif commercial contenant des nanoparticules métalliques. Parmi les métaux testés, le catalyseur à base de cérine s’avère très efficace pour réduire l’acidité des bio-huiles et catalyser la formation de dérivés phénoliques. De plus, ce catalyseur de craquage catalytique permet de réduire la teneur en oxygène de l’huile de pyrolyse et d’augmenter sa densité énergétique. Ce résultat encourageant suggère que le craquage catalytique pourrait être mis en œuvre en complément de l’hydrodésoxygénation dans une filière de production de biocarburants. Cette alternative permet de réduire le coût de l’hydrodésoxygénation et notamment la consommation de dihydrogène. / Flash pyrolysis of biomass is seen as a new way to produce bio-oils which can be converted to biofuels and chemicals. However, development of such pyrolysis processes requires implementation of an efficient and innovative catalytic strategy to deoxygenate bio-oils. Pyrolysis mechanisms involve both biomass degradation reactions - primary mechanisms - and gas phase reactions - secondary mechanisms -. As a consequence, our work has been directed along two research lines. First, we tested whether impregnating a catalyst precursor in the biomass can act on the primary pyrolysis mechanisms in order to promote deoxygenation. Then we sought to enhance the catalytic cracking of pyrolysis vapours using a heterogeneous catalyst.Pyrolysis experiments of impregnated biomass show that metal nitrate salts - Mn, Fe, Co, Ni, Cu, Zn and Ce – mainly enhance cellulose depolymerisation at the expense of its fragmentation. Moreover, nitrate anions inserted in biomass promote the production of dehydrated anhydrosugars which can be used to synthesize value-added molecules. Pyrolysis of impregnated biomass also results in the formation of a catalytically active charcoal containing metal nanoparticles. Those charcoals were successfully employed to catalyse the deoxygenation of model vapour phase compounds. However, it was found that the catalytic activity of these charcoals was limited by their low specific surface area, in comparison with the measured performance measured for commercially available activated charcoal containing metal nanoparticles. Among the tested metals, the ceria-based catalyst was found both to efficiently reduce bio-oil acidity and to enhance phenol yields. Additionally, this catalytic cracking catalyst reduces the oxygen content in the pyrolysis bio-oil and increases its heating value. This encouraging result suggests that catalytic vapour cracking could be integrated in a hydrodeoxygenation-based process to produce biofuels. This option should reduce the cost of hydrodeoxygenation and in particular the hydrogen consumption.

Over the last four decades, coral reefs have suffered a ~50% decline of across the tropics. Consequently, most research efforts have focused on the impacts of anthropogenic pressures on corals, including ocean warming, ocean acidification, and overfishing. However, recent discoveries indicate that coral reefs are becoming increasingly vulnerable to acute deoxygenation events, which can drive severe and widespread coral bleaching, and in some cases, mortality of corals and other reef organisms. On unimpacted coral reefs, dissolved oxygen (DO) availability can vary between 50% and 200% air saturation, depending on the location, proximity to the open-ocean, and time of the day. During the daytime, Symbiodiniaceae spp. produce more O$_2$ than the coral host can consume, releasing excess O$_2$ to the surrounding tissues. However, at nighttime Symbiodiniaceae spp. cease O$_2$ production. Hence, corals may suffer to O$_2$ deprivation at nighttime when the photosynthesis ceases, and holobiont respiration consumes oxygen. To assess the O$_2$ thresholds and aftereffects of two Red Sea coral species: ${{P. lobata}}$ and ${{G. fascicularis}}$ corals were exposed to reduced DO concentrations. Coral fragments from both species were exposed to one control treatment (6.8 mg O$_2$ l$^{−1}$) and three reduced DO concentrations treatments (5.25 mg O$_2$ l$^{−1}$, 3.5 mg O$_2$ l$^{−1}$, and 1.25 mg O$_2$ l$^{−1}$). Experiments were held at a stable temperature (32°C ± 0.25) and stable pH levels (pH 8.2 ± 0.08). Corals in these experiments displayed different thresholds to low O$_2$ concentrations. ${{P. lobata}}$ coral fragments didn’t exhibit any bleaching symptoms throughout complete experiment. However, ${{G. fascicularis}}$ fragments showed signs of bleaching after the third night of exposure to the low O$_2$ treatment (1.25 mg O$_2$ l$^{−1}$). Physiological variables such as maximum and effective photochemical efficiency, Chl ${{a}}$, cell density, and dark respiration experienced the lowest values under the low O$_2$ treatment for both species. These results highlight the need for further experimental assessments of deoxygenation thresholds for corals across the globe. These assessments are of great importance to create better conservation strategies for the preservation of coral reefs.