Academic literature on the topic 'Water (H[subscript]2O)'

Abstract The complex, [Cu(dmap)(OAc)(H 2O)] 2· 2H 2O (dmap = N,N-dimethylaminopropanolato, OAc = acetato) was synthesized by drop-by-drop addition of N,N-dimethylaminopropanol to copper(II) acetate dihydrate suspended in toluene. The blue crystalline product was characterized by its melting point, elemental analysis, infrared spectral study, mass analysis, thermal analysis and by the single-crystal X-ray structure analysis. Compound ( 1) crystalizes in triclinic space group, P̄1, a= 6.3716(9) Å, b= 8.2719(12) Å, c= 10.9254(16) Å, α= 79.918(2)°, β= 81.812(2)°, γ= 77.171(2)° and Z= 1. The complex ( 1) is binuclear. The copper s’ environment is square pyramidal with chelating dimethylaminopropanol rings being in the equatorial and water molecules in axial positions. Acetate ligands are attached to Cu viaoxygen, in a monodentate mode while the C=O oxygen is involved in O···H–O H-bonds with water molecules. Dimethylaminopropanol serves as a chelating as well as bridging ligand.

Recent contributions to the coordination chemistry of tetraanionic water-soluble tetraarylporphyrins, namely 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin, [1]4−, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin, [2]4−, and 5,10,15,20-tetrakis(4-hydroxidophosphorylmethylphenyl)porphyrin, [ H 43]4−, are reported. Problems with the isolation of sodium and potassium salts of [2]4− are discussed. The tetraphosphonoporphyrin H 8[3] is precipitated as a dihydrochloride H 8[3]·2 HCl , its metal complexes H 8[3-M] as such. The synthesis of salts containing Ce and Os complexes of [1]4−, Al , Ga , In , Ge , Sn , As , Sb , Mn , Mo , W , Re , Os , and Pt complexes of [2]4−, and Ni , Cu , Zn , Pt and Os complexes of [ H 43]4− as documented in publications and doctoral theses from the Darmstadt laboratory are reviewed. Some properties of the new complex salts are reported. The results of crystal structure determinations of the potassium salt of tetrakis(4-sulfonatophenyl)porphyrinatoplatinate(II), K 8[2-Pt]2·10 DMSO ·6 H 2O· C 7 H 8, and the mixed sodium-potassium salt of tetrakis(4-sulfonatophenyl)porphyrinatoaluminate, K 2 Na [ Al ( DMSO )2( tpps 4)]·8( DMSO )·2 H 2 O , are shown.

Calcium aluminate decahydrate is hexagonal with the space group P63/m and Z = 6. The compound has been named CaAl2O4·10H2O (CAH10) for decades and is known as the product obtained by hydration of CaAl2O4 (CA) in the temperature region 273–288 K – one of the main components in high-alumina cements. The lattice constants depend on the water content. Several sample preparations were used in this investigation: one CAH10, three CAD10 and one CA(D/H)10, where the latter is a zero-matrix sample showing no coherent scattering contribution from the D/H atoms in a neutron diffraction powder pattern. The crystal structure including the positions of the H/D atoms was determined from analyses of four neutron diffraction powder patterns by means of the ab initio crystal structure determination program FOX and the FULLPROF crystal structure refinement program. Additionally, eight X-ray powder diffraction patterns (Cu Kα1 and synchrotron X-rays) were used to establish phase purity. The analyses of these combined neutron and X-ray diffraction data clearly show that the previously published positions of the O atoms in the water molecules are in error. Thermogravimetric analysis of the CAD10 sample preparation used for the neutron diffraction studies gave the composition CaAl2(OD)8(D2O)2·2.42D2O. Neutron and X-ray powder diffraction data gave the structural formula CaAl2(OX)8(X 2O)2·γX 2O (X = D, H and D/H), where the γ values are sample dependent and lie between 2.3 and 3.3.

The quaternary systems Ba(OH)2—BaCl2—H2O and Ba(OH)2—BaBr2—H2O were studied with the help of X-ray and neutron diffraction as well as IR, Raman, DTA, and TG methods. The following compounds have been established or confirmed: Ba(OH)Cl · nH2O (n = 0, 1/2, 2) and Ba(OH)Br · H2O (n = 0, 1/2, 2). The crystal structures (of hitherto unknown structure type) of Ba(OH)Cl- 2 H2O and Ba(OD)Cl · 2 D2O were determined by single crystal X-ray methods and neutron powder diffraction (space group P4/nmm, Z = 2, 621 unique reflections, R = 8.8 and 1.9%, respectively). Whereas the hydroxide ion in this layer structured compound is non-hydrogen bonded, i. e. no Η-bond donor group, nor it is bound to the Ba2+ ions, the water molecules are involved in strong Η-bonds to adjacent OH- ions. The coordination of the barium ions is monocapped tetragonal antiprismatic (4 H2O and 5 halide ions). The IR and Raman spectra of Ba(OH)X · 2 H2O (X = Cl, Br) are assigned and discussed in terms of hydrogen bonding, isotopic shifts, and intermolecular coupling of the bands observed. The stretching modes of the OH- ions (3672 and 3667 cm-1, 95 K) are shifted to higher wavenumbers by about 100 cm-1 as compared with those of free OH- ions.

The title organic–inorganic hybrid salt, (C7H11N2)2[V(C2O4)2O(H2O)]·2H2O, shows a distorted octahedral coordination environment for the vanadium(IV) atom in the anion (point group symmetry 2), with four O atoms from two symmetry-related chelating oxalate dianions and two O atoms intransconfiguration from a coordinating water molecule and a terminal vanadyl O atom. In the crystal, (001) layers of cations and anions alternate along [001]. The anionic layers are built up by intermolecular O—H...O hydrogen bonds involving the coordinating and solvent water molecules. The cationic layers are linked to the anionic layersviaN—H...O hydrogen bonds between the pyridinium group and the non-coordinating O atoms of the oxalate group. The 4-(dimethylamino)pyridinium cations are also engaged in π–π stacking with their antiparallel neighbours [centroid-to-centroid distance = 3.686 (2) Å]. Considering all supramolecular features, a three-dimensional network structure is accomplished.

Ultrasonic energy was used to accelerate the formation of hydroxyapatite (HAp). The experiments were carried out in aqueous systems on two different sets of reactants: (1) a mixture of Ca4(PO4)2O(TetCP) and CaHPO4 · 2H2O (brushite) and (2) α–Ca3(PO4)2 (α–TCP). The reaction systems were exposed to ultrasound of 20 kHz for various times ranging from 5 to 80 min. The products were characterized by XRD and SEM. Parallel experiments without ultrasound were carried out for calibration. The results show that the ultrasound substantially accelerates both reactions. With ultrasound, the time required for the TetCP-brushite system to complete the reaction forming HAp was reduced from 9 h to 25 min at 25 °C, and from 3 h to 15 min at 38 °C. At 87 °C, α–TCP does not hydrolyze within 1 h in de-ionized water unless the pH is adjusted. Hydrolysis of α–TCP was induced by sonication in less than 20 min, and longer treatment results in the formation of a homogeneous sol of HAp.

Polar organic molecules are defined by differences in electronegativity between their atomic constituents and the resulting asymmetrical structures. They represent the basic chemical building blocks of life. Having a strong affinity to water (H[subscript]2O), which is essential for life on Earth, polar molecules are studied by the discipline of biochemistry and their origin, distribution, and function in living systems is relatively well understood. Polar constituents of sedimentary organic matter and petroleum have been previously studied but they are, in general, yet far from being understood. They can be present as primary biogenic molecules, rearranged biogenic molecules, or secondary functionalized hydrocarbons. The studies compiled in this thesis use selected polar organic compounds as molecular tools: phospholipids as indicators of biomass, high-molecular-weight polycyclic aromatic hydrocarbons as combustion markers, phenols as indicators of oil-water interaction processes, and carboxylic acids in general.Chapter 2 studies the biological oxidation of petroleum accumulations; a process mediated by microbes that inhabit the deep subsurface and affect the long-term storage of living carbon as sedimentary biomass of the ‘deep biosphere’. The results presented in chapter 2 suggest that intact bacterial cells are present in biodegraded petroleum, as indicated by the detection of membrane lipid fragments, termed phospholipids, in these oil samples. Carboxylic acids released from phospholipids (i.e. phospholipid fatty acids, PLFA) in oil samples vary in concentration (~2.0 - ~10.0 µg/g oil) and composition (i-C[subscript]14:0 dominated vs. i-C[subscript]15:0 and i-C[subscript]17:0 dominated) during progressive petroleum biodegradation, thereby showing that the microbial community increases in size during the removal of petroleum constituents, and that the community structure changes. Not one but at least two structurally different microbial consortia are shown to be responsible for petroleum degradation. Chapter 4 evaluates the rapid oxidation of biomass during the impact of an extraterrestrial bolide, which occurred during the late Neoproterozoic.The co-occurrence of a -3.5‰ negative sedimentary stable carbon isotope excursion and a molecular combustion-marker anomaly (coronene; 0.48 ppb, relative to a 0.04 ppb background), which are followed by a diversification of Acritarch species, suggests that combustion of ‘early’ terrestrial and marginallymarine biomass might have caused extensive smoke and atmospheric dimming, as well as subsequent photosynthetic stress. Moreover, the sharp combustion marker anomaly can probably provide a long-sought chronostratigraphic marker for the late Neoproterozoic, when also detected in other locations around the globe. Chapter 5 evaluates the effects of petroleum interaction with water. For this purpose oils produced from one reservoir were monitored during a 335-day period following the rationale that oil-water interaction increases during petroleum production. Based on a selective depletion of volatile aromatics and invariant phenol concentrations the results exclude both evaporative and oil-water partitioning processes. Petroleum compositional changes, recorded mainly in the low-molecular-weight aromatic and phenol fractions, were tentatively attributed to abiotic oxidation processes. Furthermore, methodological advances in the analysis of carboxylic acids of low molecular weight, evaluated for the execution of the other studies, are presented in chapter 4.Overall, the presented results shed more light on carbon export fluxes from different sedimentary carbon reservoirs by shedding new light on deep biosphere metabolism, elucidating the significance of the Neoproterozoic Acraman impact event, and contributing to our knowledge of petroleum destruction through its interaction with water in sedimentary basins. Moreover, they show that, in contrast to traditional belief, NSO compounds in oils and bitumens can form useful molecular tools to study questions in petroleum geochemistry, biogeochemistry, and palaeobiogeochemistry. Understanding the size of carbon reservoirs and fluxes on Earth, as well as the mechanisms that cause these carbon fluxes, can increase our appreciation of global biogeochemical cycling and, in turn, explain ecosystem dynamics, past evolutionary events, and predict future change of current climatic conditions.

Abstract: Monte Carlo simulations were used here to compare the radiation chemistry of pure water and aqueous bromide solutions after irradiation with two different types of radiation, namely, tritium β-electrons (~7.8 keV) and [superscript 60]Co γ-rays/fast electron (~1 MeV) or high energy protons. Bromide ions (Br-) are known to be selective scavengers of hydroxyl radicals •OH precursors of hydrogen peroxide H[subscript 2]O[subscript 2]. These simulations thus allowed us to determine the yields (or G-values) of H[subscript 2]O[subscript 2] in the radiolysis of dilute aqueous bromide solutions by the two types of radiations studied, the first with low linear energy transfer (LET) (~0.3 keV/μm) and the second with high LET (~6 keV/μm) at 25 °C. This study was carried out under a wide range of Br- concentrations both in the presence and the absence of oxygen. Simulations clearly showed that irradiation by tritium β-electrons favored a clear increase in G(H[subscript 2]O[subscript 2]) compared to [superscript 60]Co γ-rays. We found that these changes could be related to differences in the initial spatial distributions of radiolytic species (i.e., the structure of the electron tracks, the low-energy β-electrons of tritium depositing their energy as cylindrical “short tracks” and the energetic Compton electrons produced by γ-radiolysis forming mainly spherical “spurs”). Moreover, simulations also showed that the presence of oxygen, a very good scavenger of hydrated electrons (e-[subscript aq]) and H• atoms on the 10[superscript-7] s time scale (i.e., before the end of spur expansion), protected H[subscript 2]O[subscript 2] from further reactions with these species in the homogeneous stage of radiolysis. This protection against e-[subscript aq] and H• atoms therefore led to an increase in the H[subscript 2]O[subscript 2] yields at long times, as seen experimentally. Finally, for both deaerated and aerated solutions, the H[subscript 2]O[subscript 2] yield in tritium β-radiolysis was found to be more easily suppressed than in the case of cobalt-60 γ-radiolysis, and interpreted by the quantitatively different chemistry between short tracks and spurs. These differences in the scavengeability of H[subscript 2]O[subscript 2] precursors in passing from low-LET [superscript 60]Co γ-ray to high-LET tritium β-electron irradiation were in good agreement with experimental data, thereby lending strong support to the picture of tritium-β radiolysis in terms of short tracks of high local LET.
Résumé: Les simulations Monte Carlo constituent une approche théorique efficace pour étudier la chimie sous rayonnement de l'eau et des solutions aqueuses. Dans ce travail, nous avons utilisé ces simulations pour comparer l’action de deux types de rayonnement, à savoir, le rayonnement γ de [indice supérieur 60]Co (électrons de Compton ~1 Me V) et les électrons β du tritium (~ 7,8 keV), sur la radiolyse de l’eau et des solutions aqueuses diluées de bromure. Les ions Br- sont connus comme d’excellents capteurs des radicaux hydroxyles •OH, précurseurs du peroxyde d’hydrogène H[indice inférieur 2]O[indice inférieur 2]. Les simulations Monte Carlo nous ont donc permis de déterminer les rendements (ou valeurs G) de H[indice inférieur 2]O[indice inférieur 2] à 25 °C pour les deux types de rayonnements étudiés, le premier à faible transfert d'énergie linéaire (TEL) (~0,3 keV/μm) et le second à haut TEL (~6 keV/μm). L’étude a été menée pour différentes concentrations d’ions Br-, à la fois en présence et en absence d'oxygène. Les simulations ont montré que l’irradiation par les électrons β du tritium favorisait nettement la formation de H[indice inférieur 2]O[indice inférieur 2] comparativement aux rayons γ du cobalt. Ces changements ont pu être reliés aux différences qui existent dans les distributions spatiales initiales des espèces radiolytiques (i.e., la structure des trajectoires d'électrons, les électrons β du tritium déposant leur énergie sous forme de «trajectoires courtes» de nature cylindrique, et les électrons Compton produits par la radiolyse γ formant principalement des «grappes» de géométrie plus ou moins sphérique). Les simulations ont montré également que la présence d'oxygène, capteur d’électrons hydratés et d’atomes H• sur l'échelle de temps de ~10[indice supérieur -7] s (i.e., avant la fin des grappes), protégeait H[indice inférieur 2]O[indice inférieur 2] d’éventuelles réactions subséquentes avec ces espèces. Une telle «protection» conduit ainsi à une augmentation de G(H[indice inférieur 2]O[indice inférieur 2]) à temps longs. Enfin, en milieu tant désaéré qu’aéré, les rendements en H[indice inférieur 2]O[indice inférieur 2] obtenus lors de la radiolyse par les électrons β du tritium ont été trouvés plus facilement supprimés que lors de la radiolyse γ. Ces différences dans l’efficacité de capture des précurseurs de H[indice inférieur 2]O[indice inférieur 2] ont été interprétées par les différences quantitatives dans la chimie intervenant dans les trajectoires courtes et les grappes. Un excellent accord a été obtenu avec les données expérimentales existantes.

Résumé : Le contrôle de la chimie de l'eau dans un réacteur nucléaire refroidi à l'eau nécessite une compréhension détaillée des effets de la radiolysede l'eau afin de limiter la corrosion et la dégradation des matériaux par oxydation générée par les produits de cette radiolyse. Toutefois, la mesure directe de la chimie dans le cœur des réacteurs est extrêmement difficile, sinon impossible, en raison des conditions extrêmes de haute température et haute pression, et les champs d’irradiation mixtes neutrons/γ, qui ne sont pas compatibles avec l'instrumentation chimique normale. Pour ces raisons,des modèles théoriques et des simulations sur ordinateur sont essentielles pour la prédiction de la chimie sous rayonnement de l'eau de refroidissement dans le cœur et son impact sur les matériaux. Dans ce travail, des simulations Monte Carlo ont été utilisées pour calculer les rendements des principales espèces (e[indice supérieur -][indice inférieur aq], H[indice supérieur •], H[indice inférieur 2], [indice supérieur •]OH et H[indice inférieur 2]O[indice inférieur 2]) formées lors de la radiolyse de l’eau liquide neutre par des neutrons mono-énergétiques de 2 MeV à des températures entre 25 et 350 °C. Le choix des neutrons de 2 MeV comme énergie d'intérêt est représentatif du flux de neutrons rapides dans un réacteur. Pour l'eau légère, la contribution la plus significative à la radiolyse vient des quatre premières collisions des neutrons qui produisent, dans la majorité des cas, des protons avec des énergies de recul de ~1.264, 0.465, 0.171 et 0.063 MeV et des transferts d’énergie linéique (TEL) moyens respectivement de ~22, 43, 69et 76 keV/[micro]m. Par ailleurs, nous avons négligé les effets des radiations dus aux ions de recul de l’oxygène. Les rendements moyens finaux peuvent alors être estimés comme étant la somme des rendements résultant de l’action de ces protons après pondérations en fonction de l’énergie déposée. Les rendements ont été calculés à 10[indice supérieur -7], 10[indice supérieur -6] et 10[indice supérieur -5] s. Les valeurs obtenues sont en accord avec les données expérimentales disponibles. En comparant nos résultats avec les données obtenues pour les rayonnements à faible TEL (rayons γ de [indice supérieur 60]Co ou électrons rapides), nos rendements calculés pour les neutrons rapides ont montré une dépendance en température essentiellement similaire, mais avec des valeurs plus faibles pour les rendements en radicaux libres et des valeurs plus élevées pour les rendements moléculaires. Nous avons également utilisé les simulations Monte Carlo pour étudier l'existence de la chute rapide de la constante de vitesse de réaction de l'électron hydraté (e[indice supérieur -][indice inférieur aq]) sur lui-même – l’une des principales sources de formation de H[indice inférieur 2] – au-dessus de 150 °C. Cette dépendance en température a été observée expérimentalement en milieu alcalin par divers auteurs, mais jamais en milieu neutre. Lorsque cette baisse de la constante de vitesse d’auto-réaction de e[indice supérieur -][indice inférieur aq] est incluse dans nos codes de simulation, tant pour des rayonnements de bas TEL (grappes isolés) que de haut TEL (trajectoires cylindriques), g(H[indice inférieur 2]) montre une discontinuité marquée à la baisse à ~150°C, ce qui n'est pas observée expérimentalement. Les conséquences de la présence de cette discontinuité dans le rendement en H[indice inférieur 2] pour les rayonnements à bas et haut TEL sont discutées. Enfin, nous avons tenté d’expliquer l'augmentation – considérée comme anormale – du rendement en H[indice inférieur 2] en fonction de la température au-dessus de 200 °C par l’intervention de la réaction des atomes H[indice supérieur •] avec l'eau, préalablement proposée par Swiatła-Wojcik et Buxton en 2005. La constante de vitesse de cette réaction est toujours controversée. // Abstract : Controlling the water chemistry in a water-cooled nuclear power reactor requires understanding and mitigating the effects of water radiolysis to limit the corrosion and degradation of materials by oxidizing radiolysis products. However, direct measurement of the chemistry in reactor cores is extremely difficult due to the extreme conditions of high temperature, pressure, and mixed neutron/γ-radiation fields, which are not compatible with normal chemical instrumentation. For these reasons, theoretical models and computer simulations are essential for predicting the detailed radiation chemistry of the cooling water in the core and the impact on materials. Monte Carlo simulations were used to calculate the yields for the primary species (e[superscript -][subscript aq], H[superscript •], H[subscript 2], [superscript •]OH, and H[subscript 2]O[subscript 2]) formed from the radiolysis of neutral liquid water by mono-energetic 2-MeV neutrons and the mechanisms involved at temperatures between 25 and 350 °C. In this work, we chose 2-MeV neutron as our energy of interest since it is known as representative of a fast neutron flux in a nuclear reactor. For light water, for that chosen energy, the most significant contribution to the radiolysis comes from the first four neutron collisions that generate mostly ejected protons with energies of ~1.264, 0.465, 0.171, and 0.063 MeV, which had, at 25 °C, mean linear energy transfers (LETs) of ~22, 43, 69, and 76 keV/[micro]m, respectively. In this work, we simply neglected the radiation effects due to oxygen ion recoils. The average final fast neutron yields could be estimated as the sum of the yields for these protons after allowance was made for the appropriate weightings (by using the Eq (2) in Chapter 4) according to their deposited energy. Yields were calculated at 10[superscript -7], 10[superscript -6] and 10[superscript -5] s. Our computed yield agreed reasonably well with the available experimental data. By comparing our results with data obtained for low-LET radiation ([superscript 60]Co γ-rays or fast electrons), our computed yields for fast neutron radiation showed essentially similar temperature dependences over the range of temperature studied, but with lower values for yields of free radicals and higher values for molecular yields. In this work, we also used our Monte Carlo simulation to investigate the existence of drop of hydrated electron (e[superscript -][subscript aq]) self-reaction rate constant at 150 °C. One of the main sources of H[subscript 2] formation is the self-reaction of hydrated electrons. The temperature dependence of the rate constant of this reaction (k[subscript 1]), measured under alkaline conditions, reveals that the rate constant drops abruptly above ~150 °C. However, when this drop in the e[superscript -][subscript aq] self-reaction rate constant is included in our code for low (isolated spurs) and high (cylindrical tracks) linear energy transfer (LET), g(H[subscript 2]) shows a marked downward discontinuity at ~150 °C which is not observed experimentally. The consequences of the presence of this discontinuity in H[subscript 2] yield for both low and high LET radiation are discussed. Another reaction that might explain the anomalous increasing of H[subscript 2] yield with temperature is the reaction of H[superscript •] atoms with water previously proposed by Swiatla-Wojcik and Buxton (2005) whose rate constant is still in controversial.