49 research outputs found
高酸化度化学種を利用した炭素-炭素不飽和結合の修飾
No full textCarbon-Carbon (C-C) multiple bonds, serving as the cornerstone of many organic compounds extracted from petroleum resources and obtained from natural origins, act as key site for functional group attachment, thereby enabling the evolution of base molecules into value-added, complex chemical structures. This bond serves as a fertile platform for functional group introduction, facilitating the transformation of base molecules into more complex structures with considerably higher value. Carbon-Carbon multiple bonds exhibit inherent nucleophilic characteristics primarily due to their rich electron density. This unique property makes them particularly attractive in organic synthesis as they are amenable to modifications through a diverse array of reactions with electrophilic counterparts. The hydration reaction, carried out in acidic aqueous solutions such as sulfuric acid, stands as a classic example of the potential for multiple bond modification. Harnessing the reactivity of C-C multiple bonds for functionalization necessitates the creation of highly electrophilic active species. One prevalent strategy to achieve this involves the employment of high oxidation state chemical species. Such chemical species are inherently electron-deficient due to their high oxidation state, thereby exhibiting enhanced electrophilicity. This characteristic makes them ideal for initiating reactions with electron-rich C-C multiple bonds. The use of high oxidation state chemical species, hence, presents a compelling route to the functionalization of C-C multiple bonds. I delve into this topic further by categorizing these reactions into two primary types: those catalyzed by transition metals and those involving nonmetallic chemical species. In the sections that follow, these reactions will be analyzed, aiming to uncover the full potential of C-C multiple bond modification reactions using high oxidation state chemical species
Functionalization of Carbon-Carbon Multiple Bonds by High Oxidation State Chemical Species [an abstract of dissertation and a summary of dissertation review]
No full text(主査) 教授 永木 愛一郎, 教授 澤村 正也, 教授 伊藤 肇, 准教授 清水 洋平総合化学院（総合化学専攻
Functionalization of Carbon-Carbon Multiple Bonds by High Oxidation State Chemical Species
No full textCarbon-Carbon (C-C) multiple bonds, serving as the cornerstone of many organic compounds extracted from petroleum resources and obtained from natural origins, act as key site for functional group attachment, thereby enabling the evolution of base molecules into value-added, complex chemical structures. This bond serves as a fertile platform for functional group introduction, facilitating the transformation of base molecules into more complex structures with considerably higher value. Carbon-Carbon multiple bonds exhibit inherent nucleophilic characteristics primarily due to their rich electron density. This unique property makes them particularly attractive in organic synthesis as they are amenable to modifications through a diverse array of reactions with electrophilic counterparts. The hydration reaction, carried out in acidic aqueous solutions such as sulfuric acid, stands as a classic example of the potential for multiple bond modification. Harnessing the reactivity of C-C multiple bonds for functionalization necessitates the creation of highly electrophilic active species. One prevalent strategy to achieve this involves the employment of high oxidation state chemical species. Such chemical species are inherently electron-deficient due to their high oxidation state, thereby exhibiting enhanced electrophilicity. This characteristic makes them ideal for initiating reactions with electron-rich C-C multiple bonds. The use of high oxidation state chemical species, hence, presents a compelling route to the functionalization of C-C multiple bonds. I delve into this topic further by categorizing these reactions into two primary types: those catalyzed by transition metals and those involving nonmetallic chemical species. In the sections that follow, these reactions will be analyzed, aiming to uncover the full potential of C-C multiple bond modification reactions using high oxidation state chemical species.(主査) 教授 永木 愛一郎, 教授 澤村 正也, 教授 伊藤 肇, 准教授 清水 洋平総合化学院（総合化学専攻
Synthesis of C,N,N-Cyclometalated Gold(III) Complexes with Anionic Amide Ligands
No full textA series of neutral C,N,N Au(III) complexes were synthesized with N -(8-quinolinyl)benzamide derivatives or chiral N -[2-(1,3-oxazolin-2-yl)phenyl]benzamide derivatives. The convenient synthesis method for the amide ligands, together with their operationally simple complexation by direct C-H auration, permitted changes to both the steric and electronic properties of Au(III) complexes for promoting the catalytic three-component couplings of an aldehyde, an amine, and an alkyne
Modeling of Evaporation-Driven Multiple Salt Precipitation in Porous Media with a Real Field Application
No full textSoil and groundwater salinization are very important environmental issues of global concern. They threaten mainly the arid and semiarid regions characterized by dry climate conditions and an increase of irrigation practices. Among these regions, the south of Tunisia is considered, on the one hand, to be a salt-affected zone facing a twofold problem: The scarcity of water resources and the degradation of their quality due to the overexploitation of the aquifers for irrigation needs. On the other hand, this Tunisian landform is the only adequate area for planting date palm trees which provide the country with the first and most important exportation product. In order to maintain the existence of these oases and develop the date production, a good understanding of the salinization problem threatening this region, and the ability to predict its distribution and evolution, should not be underestimated. The work presented in this paper deals with the Oasis of Segdoud in southern Tunisia, with the objective of modeling the evaporation-driven salt precipitation processes at the soil profile scale and under real climatic conditions. The model used is based on the one developed and presented in a previous work. In order to fulfil the real field conditions, a further extension of the geochemical system of the existing model was required. The precipitated salts considered in this work were halite (NaCl), gypsum (CaSO4) and thenardite (Na2SO4). The extended model reproduces very well the same tendencies of the physico-chemical processes of the natural system in terms of the spatio-temporal distribution and evolution of the evaporation and multiple-salt precipitation. It sheds new lights on the simulation of sequences of salt precipitation in arid regions. The simulation results provide an analysis of the influence of salt precipitation on hydrodynamic properties of the porous medium (porosity and permeability). Moreover, the sensitivity analysis done here reveals the influence of the water table level on the evaporation rate
Demonstration of facilitation between microalgae to face environmental stress
No full textAuthor Correction: Demonstration of facilitation between microalgae to face environmental stress. In Scientific Reports, vol; 10, n°1, Article : 3557 ; DOI: 10.1038/s41598-020-59860-0 ; WOS:000563252500001 Author Correction: Demonstration of facilitation between microalgae to face environmental stress. In Scientific Reports, vol; 10, n°1, Article : 3557 ; DOI: 10.1038/s41598-020-59860-0 ; WOS:000563252500001The original version of this Article omitted an affiliation for Emna Krichen and the Acknowledgements section contained typographical errors and was incomplete. This erratum is available as an annex file.International audiencePositive interactions such as facilitation play an important role during the biological colonization and species succession in harsh or changing environments. However, the direct evidence of such ecological interaction in microbial communities remains rare. Using common freshwater microalgae isolated from a High Rate Algal Pond HRAP treating wastewaters, we investigated with both experimental and modeling approaches the direct facilitation between two algal strains during the colonization phase. Our results demonstrate that the first colonization by microalgae under a severe chemical condition arose from the rapid growth of pioneer species such as Chlorella sorokiniana, which facilitated the subsequent colonization of low growth specialists such as Scenedesmus pectinatus. The pioneer species rapidly depleted the total available ammonia nitrogen favoring the specialist species initially inhibited by free ammonia toxicity. This latter species ultimately dominated the algal community through competitive exclusion under low nutrient conditions. We show that microbial successions are not only regulated by climatic conditions but also by interactions between species based on the ability to modify their growth conditions. We suggest that facilitation within the aquatic microbial communities is a widespread ecological interaction under a vast range of environmental stress
Modeling of evaporation-driven multiple salt precipitation in porous media with a real field application
No full textSoil and groundwater salinization are very important environmental issues of global concern. They threaten mainly the arid and semiarid regions characterized by dry climate conditions and an increase of irrigation practices. Among these regions, the south of Tunisia is considered, on the one hand, to be a salt-affected zone facing a twofold problem: The scarcity of water resources and the degradation of their quality due to the overexploitation of the aquifers for irrigation needs. On the other hand, this Tunisian landform is the only adequate area for planting date palm trees which provide the country with the first and most important exportation product. In order to maintain the existence of these oases and develop the date production, a good understanding of the salinization problem threatening this region, and the ability to predict its distribution and evolution, should not be underestimated. The work presented in this paper deals with the Oasis of Segdoud in southern Tunisia, with the objective of modeling the evaporation-driven salt precipitation processes at the soil profile scale and under real climatic conditions. The model used is based on the one developed and presented in a previous work. In order to fulfil the real field conditions, a further extension of the geochemical system of the existing model was required. The precipitated salts considered in this work were halite (NaCl), gypsum (CaSO4) and thenardite (Na2SO4). The extended model reproduces very well the same tendencies of the physico-chemical processes of the natural system in terms of the spatio-temporal distribution and evolution of the evaporation and multiple-salt precipitation. It sheds new lights on the simulation of sequences of salt precipitation in arid regions. The simulation results provide an analysis of the influence of salt precipitation on hydrodynamic properties of the porous medium (porosity and permeability). Moreover, the sensitivity analysis done here reveals the influence of the water table level on the evaporation rate
