Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Hydroxides”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 721 records · Page 40Linked to original sources
PubMed2002

Triple-quantum magic angle spinning (27)Al NMR of aluminum hydroxides.

We show that (27)Al triple-quantum magic angle spinning (3Q-MAS) experiments alleviate the second-order quadrupolar broadening to reveal the structure-building units of nonequivalent aluminum octahedra in the most extensively studied aluminum hydroxides, namely, gibbsite, bayerite, and boehmite. Further, aided by ab initio calculations of the electric field gradient tensors, the 3Q-MAS/MAS results are shown to lead to the assignment of (27)Al isotropic resonances to the aluminum positions in their X-ray-determined structures. The present work paves the way for future studies on various structurally transformed materials derived from these basic aluminum hydroxides.

Journal Article↗
PubMed2002

Layered double hydroxide supported nanopalladium catalyst for Heck-, Suzuki-, Sonogashira-, and Stille-type coupling reactions of chloroarenes.

Layered double hydroxide and Merrifield resin supported nanopalladium(0) catalysts are prepared by an exchange of PdCl(4)(2-) followed by reduction and well characterized for the first time. The ligand-free heterogeneous layered double hydroxide supported nanopalladium (LDH-Pd(0)) catalyst using the basic LDH in place of basic ligands indeed exhibits higher activity and selectivity in the Heck olefination of electron-poor and electron-rich chloroarenes in nonaqueous ionic liquids (NAIL) over the homogeneous PdCl(2) system. Using microwave irradiation, the rate of the Heck olefination reaction is accelerated, manifold with the highest turnover frequency ever recorded in the case of both electron-poor and electron-rich chloroarenes. The basic LDH-Pd(0) shows a superior activity over a range of supported catalysts, from acidic to weakly basic Pd/C, Pd/SiO(2,) Pd/Al(2)O(3), and resin-PdCl(4)(2-) in the Heck olefination of deactivated electron-rich 4-chloroanisole. The use of LDH-Pd(0) is extended to the Suzuki-, Sonogashira-, and Stille-type coupling reactions of chloroarenes in an effort to understand the scope and utility of the reaction. The catalyst is quantitatively recovered from the reaction by a simple filtration and reused for a number of cycles with almost consistent activity in all the coupling reactions. The heterogeneity studies provide an insight into mechanistic aspects of the Heck olefination reaction and evidence that the reaction proceeds on the surface of the nanopalladium particles of the heterogeneous catalyst. TEM images of the fresh and used catalyst indeed show that the nanostructured palladium supported on LDH remains unchanged at the end of the reaction, while the XPS and evolved gas detection by TGA-MS of the used catalyst identify ArPdX species on the heterogeneous surface. Thus, the ligand-free nanopalladium supported on LDH, synthesized by the simple protocol, displays superior activity over the other heterogeneous catalysts inclusive of nanopalladium in the C-C coupling reactions of chloroarenes.

Journal Article↗
PubMed2006

A well-defined hydrocarbon-soluble calcium hydroxide: synthesis, structure, and reactivity.

Controlled hydrolysis of a (beta-diketiminate)calcium-amide gave a heteroleptic (beta-diketiminate)calcium-hydroxide complex that is remarkably stable against ligand exchange and formation of Ca(OH)2. The structure of this dimeric complex shows OH- units that symmetrically bridge the Ca2+ ions. This hydrocarbon-soluble calcium hydroxide reacted rapidly with CO2 to produce a gel from which amorphous CaCO3 slowly separated. This reaction behavior allows for sol-gel coating with CaCO3 from an organic solvent. Reaction with benzophenone did not lead to nucleophilic attack of OH- to the carbonyl but gave a red benzophenone adduct instead.

Journal Article↗
PubMed2003

Catalytic alkynylation of ketones and aldehydes using quaternary ammonium hydroxide base.

Catalytic alkynylation of diverse ketones and aldehydes using nonmetallic benzyltrimethylammonium hydroxide or a basic resin of the hydroxide type in DMSO is described. Aliphatic or alicyclic carbonyl partners gave satisfactory results, whereas aromatic ones afforded products with low yields. When aromatic aldehydes were reacted with phenylacetylene, enones such as chalcone derivatives were obtained in place of ynols. These organobase-catalyzed systems provide a practical nonmetallic protocol for C[bond]C formation.

Journal Article↗
PubMed2004

Photonucleophilic aromatic substitution of 6-fluoroquinolones in basic media: triplet quenching by hydroxide anion.

Photoreaction of 1-ethyl-6-fluoro-7-(1-piperazinyl)-1,4-dihydro-4-oxoquinoline-3-carboxylic acid (norfloxacin, NFX) and other 6-fluoroquinolones in aqueous solution gives rise to the corresponding 6-hydroxy derivatives. Although two mechanisms have been proposed for this photonucleophilic aromatic substitution, direct evidence for any of them is still missing. Obtaining such evidence requires work in basic media, where intramolecular electron transfer from the piperazine ring to the quinolone system is the almost exclusive singlet deactivation pathway. To overcome this problem, the 4'-N-acetyl derivative of norfloxacin (ANFX) has been employed in the present paper due to the lower availability of the N lone pair. The photochemical and photophysical properties of ANFX have been studied in aqueous solutions at pH between 7.4 and 13. As expected, fluorescence of ANFX is not significantly quenched in basic media. Furthermore, the excited triplet state (lambda(max) = 620 nm) reacts with hydroxide anions with a rate constant of (0.3 +/- 0.1) x 10(6) M(-)(1) s(-)(1). This supports a direct attack by hydroxide anions to the excited triplet state with subsequent release of fluoride as the operating mechanism. The fact that the reaction is inhibited by the presence of naproxen (a water-soluble naphthalene derivative) as triplet quencher clearly confirms the mechanistic assignment.

Journal Article↗
PubMed2005

Synthesis of CoOOH nanorods and application as coating materials of nickel hydroxide for high temperature Ni-MH cells.

Studies on nanoscale materials have received great interest in both fundamental and applied aspects in recent years. In this letter, we report the synthesis of CoOOH nanorods and their possible applications as coating materials on nickel hydroxide for high-temperature nickel-metal hydride (Ni-MH) cells. The morphology and structure of CoOOH nanorods and coated nickel hydroxide particles are investigated by transmission electron microscopy, X-ray diffraction, and scanning electron microscopy, respectively. The electrochemical properties in the cylindrical AA size Ni-MH cells are evaluated. Our results show that the Ni-MH cells, where the positive electrodes are composed of such nanometer sized CoOOH coatings, have a higher capacity available and good performance at elevated temperatures of >50 degrees C.

Journal Article↗
PubMed2005

High-yield preparation of uniform cobalt hydroxide and oxide nanoplatelets and their characterization.

Cobalt hydroxide nanoplatelets with a uniform hexagonal shape were prepared in high yield ( approximately 95%) by a facile hydrothermal route in the presence of poly(vinylpyrrolidone). This method provides a simple, low-cost, and large-scale route to produce beta-cobalt hydroxide nanoplatelets with an average diameter of 280 nm and a thickness of ca. 26 nm which show a predominant well-crystalline hexagonal brucite-like phase. Their thermal decomposition produced anisotropic nanoplatelets of cobalt oxides (CoO and Co3O4) under designed temperatures. The products were characterized by transmission electronic microscopy, selected-area electron diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetric, and thermogravimetric analysis. The magnetic properties of the products were investigated by a superconducting quantum interference device magnetometer. Co3O4 nanoplatelets exhibit a superparamagnetic behavior, and they might be a promising material to study the magnetic tunneling effect as anisotropic nanostructures.

Journal Article↗
PubMed2006

Hexamethylenetetramine directed synthesis and properties of a new family of alpha-nickel hydroxide organic-inorganic hybrid materials with high chemical stability.

A new family of organic-inorganic hybrid material of alpha-nickel hydroxide formulated as Ni(OH)2-x(An-)x/n-(C6H12N4)y.zH2O (A=Cl-, CH3COO-, SO4(2-), NO3-; x=0.05-0.18, y=0.09-0.11, z=0.36-0.43) with high stability and adjustable interlayer spacing ranging from 7.21 to 15.12 A has been successfully prepared by a simple hydrothermal method. The effects of various anions and hexamethylenetetramine (HMT) on the d values of alpha-nickel hydroxide have been systematically investigated. This family of hybrid materials is of such high stability that they can stand more than 40 days in 6 M KOH. The product with a formula Ni(OH)1.95(C6H12N4)0.11(Cl-)0.05(H2O)0.36 has a high surface area of about 299.26 m2/g and an average pore diameter of about 45.1 A. The coercivity (Hc) value is ca. 2000 Oe for the sample with a d spacing of 13.14 A. Moreover, the prepared alpha-Ni(OH)2 in our experiment is of high stability in strong alkali solution. Such high stability could be derived from strong chelating interactions between the Ni ions and HMT molecules with the interlayers. This high chemical stability could make this material more suitable for the applications.

Journal Article↗
PubMed2006

Infrared spectra of M(OH)(1,2,3) (M = Mn, Fe, Co, Ni) molecules in solid argon and the character of first row transition metal hydroxide bonding.

Reactions of laser-ablated Mn, Fe, Co, and Ni atoms with H(2)O(2) and with H(2) + O(2) mixtures in excess argon give new absorptions in the O-H and M-O stretching regions, which are assigned to metal dihydroxide and trihydroxide molecules, M(OH)(2) and M(OH)(3). Isotopic substitutions (D(2)O(2), (18)O(2), (16,18)O(2), D(2)) confirmed the assignments and DFT calculations reproduced the experimental results. The O-H stretching frequencies decreased in the dihydroxides from Sc to Zn. Mulliken and natural charge distributions indicate significant electron transfer from metal d orbitals to OH ligands that decreases from Sc to Zn, suggesting that the early transition metal hydroxides are more ionic and that the later transition metal hydroxides are more covalent.

Journal Article↗
PubMed2003

New synthetic route for organic polyoxometallic clusters: synthetic and structural investigations on the first dumb-bell shaped polyoxozirconium hydroxide with the [Zr9(mu5-O)2(mu3-O)4(mu-O)4(mu-OH)8] core structure.

A new route for organic polyoxometallic clusters describes the first dumb-bell-like organic polyoxozirconium hydroxide [[(Cp*Zr)4(mu5-O)(mu3-O)2(mu-OH)4]2Zr(mu-O)4] x 2C7H8 (2; Cp* = C5Me5) involving the treatment of the Brønsted acidic organozirconium hydroxide [(Cp*Zr)6(mu4-O)(mu-O)4(mu-OH)8] x 2C7H8 (1) with organozirconium compounds.

Journal Article↗
PubMed1999

Kinetic analysis of 52Fe-labelled iron(III) hydroxide-sucrose complex following bolus administration using positron emission tomography.

Kinetic analysis of a single intravenous injection of 100 mg iron(III) hydroxide-sucrose complex (Venofer) mixed with 52Fe(III) hydroxide-sucrose as a tracer was followed for 3-6 h in four generally anaesthetized, artificially ventilated minipigs using positron emission tomography (PET). The amount of injected radioactivity ranged from 30 to 200 MBq. Blood radioactivity, measured by PET in the left ventricle of the heart, displayed a fast clearance phase followed by a slow one. In the liver and bone marrow a fast radioactivity uptake occurred during the first 30 min, followed by a slower steady increase. In the liver a slight decrease in radioactivity uptake was noted by the end of the study. A kinetic analysis using a three-compartment (namely blood pool, reversible and irreversible tissue pools) model showed a fairly high distribution volume in the liver as compared with the bone marrow. In conclusion, the pharmacokinetics of the injected complex was clearly visualized with the PET technique. The organs of particular interest, namely the heart (for blood kinetics), liver and bone marrow could all be viewed by a single setting of a PET tomograph with an axial field of view of 10 cm. The half-life (T1/2) of 52Fe (8.3 h) enables a detailed kinetic study up to 24 h. A novel method was introduced to verify the actual 52Fe contribution to the PET images by removing the interfering radioactive daughter 52mMn positron emissions. The kinetic data fitted the three-compartment model, from which rate constants could be obtained for iron transfer from the blood to a pool of iron in bone marrow or liver to which it was bound during the study period. In addition, there was a reversible tissue pool of iron, which in the liver slowly equilibrated with the blood, to give a net efflux from the liver some hours after i.v. administration. The liver uptake showed a relatively long distribution phase, whereas the injected iron was immediately incorporated into the bone marrow. Various transport mechanisms seem to be involved in the handling of the injected iron complex.

Bone Marrow↗
PubMed2004

Ultrafast dynamics for electron photodetachment from aqueous hydroxide.

Charge-transfer-to-solvent reactions of hydroxide induced by 200 nm monophotonic or 337 and 389 nm biphotonic excitation of this anion in aqueous solution have been studied by means of pump-probe ultrafast laser spectroscopy. Transient absorption kinetics of the hydrated electron, e(aq) (-), have been observed, from a few hundred femtoseconds out to 600 ps, and studied as function of hydroxide concentration and temperature. The geminate decay kinetics are bimodal, with a fast exponential component ( approximately 13 ps) and a slower power "tail" due to the diffusional escape of the electrons. For the biphotonic excitation, the extrapolated fraction of escaped electrons is 1.8 times higher than for the monophotonic 200 nm excitation (31% versus 17.5% at 25 degrees C, respectively), due to the broadening of the electron distribution. The biphotonic electron detachment is very inefficient; the corresponding absorption coefficient at 400 nm is <4 cm TW(-1) M(-1) (assuming unity quantum efficiency for the photodetachment). For [OH(-)] between 10 mM and 10 M, almost no concentration dependence of the time profiles of solvated electron kinetics was observed. At higher temperature, the escape fraction of the electrons increases with a slope of 3x10(-3) K(-1) and the recombination and diffusion-controlled dissociation of the close pairs become faster. Activation energies of 8.3 and 22.3 kJ/mol for these two processes were obtained. The semianalytical theory of Shushin for diffusion controlled reactions in the central force field was used to model the geminate dynamics. The implications of these results for photoionization of water are discussed.

Journal Article↗
PubMed2005

Ions in water: the microscopic structure of concentrated hydroxide solutions.

Neutron-diffraction data on aqueous solutions of hydroxides, at solute concentrations ranging from 1 solute per 12 water molecules to 1 solute per 3 water molecules, are analyzed by means of a Monte Carlo simulation (empirical potential structure refinement), in order to determine the hydration shell of the OH- in the presence of the smaller alkali metal ions. It is demonstrated that the symmetry argument between H+ and OH- cannot be used, at least in the liquid phase at such high concentrations, for determining the hydroxide hydration shell. Water molecules in the hydration shell of K+ orient their dipole moment at about 45 degrees from the K+-water oxygen director, instead of radially as in the case of the Li+ and Na+ hydration shells. The K+-water oxygen radial distribution function shows a shallower first minimum compared to the other cation-water oxygen functions. The influence of the solutes on the water-water radial distribution functions is shown to have an effect on the water structure equivalent to an increase in the pressure of the water, depending on both ion concentration and ionic radius. The changes of the water structure in the presence of charged solutes and the differences among the hydration shells of the different cations are used to present a qualitative explanation of the observed cation mobility.

Journal Article↗
PubMed1995

Effects of Aluminum/Magnesium Hydroxide and Calcium Carbonate on Esophageal and Gastric pH in Subjects with Heartburn.

This single-blind crossover trial compared the effects of single oral doses of two antacids on esophageal and gastric pH in subjects with heartburn. Gastric and esophageal pH were assessed in 83 subjects from 1 h before to 4 h after a refluxogenic meal. Subjects received two chewable tablets of a high-potency aluminum/magnesium hydroxide [Al(OH)3/Mg(OH)2] formulation (Mylanta Double-Strength(TM)) or a calcium carbonate [CaCO3] formulation (Tums E-X(TM)), or placebo 1 h after the meal. Both antacid formulations significantly increased esophageal pH, as compared with placebo. Onset of action was faster with the Al(OH)3/Mg(OH)2 formulation than with the CaCO3 in 41 subjects, slower in 13 subjects, and identical in 29 subjects. Area under the esophageal pH--time curves after dosing were significantly greater for Al(OH)3/Mg(OH)2 than for CaCO3 (p < 0.05) and significantly greater for CaCO3 than for placebo (p < 0.05). The duration of Al(OH)3/Mg(OH)2 action in the esophagus was 82 min and 60 min for CaCO3 (p < 0.05). In the stomach, only Al(OH)3/Mg(OH)2 increased gastric pH compared with placebo. After ingestion of calcium carbonate, gastric pH usually remained at or below placebo values, a finding consistent with a calcium carbonate-induced "acid rebound." The duration of Al(OH)3/Mg(OH)2 action in the stomach was 26 min. These findings demonstrate the efficacy and relative superiority of this particular aluminum/magnesium hydroxide formulation compared with the calcium carbonate preparation at increasing esophageal and gastric pH. However, the magnitude and duration of action of both antacids on esophageal pH, in contrast to minimal effects on gastric pH, suggest strongly that the lower esophagus is the primary site of antacid activity in relief of heartburn.

Journal Article↗
PubMed1990

Permeability of the pineal gland of the viscacha (Lagostomus maximus maximus) to the lanthanum hydroxide.

Lanthanum hydroxide together with a fixative solution was injected into the third ventricle of the viscacha. The tracer penetrated freely into the pineal gland demonstrating an extensive network of intercommunicating intercellular spaces. Numerous gap junctions were observed indicating that they are the predominant interparenchymal contacts. The capillaries were characterized by non-fenestrated endothelial cells lining a moderate-sized perivascular space. Precipitates of lanthanum hydroxide were found in the basal membranes of the perivascular and interendothelial spaces, but not in the vascular lumina. The tracer stopped at tight junctions; these constitute a barrier between the pinealocytes and the blood compartment. Active micropinocytosis observed in the capillary walls suggest a transendothelial transport.

Animals↗
PubMed1976

Distribution of yttrium 90 ferric hydroxide colloid and gold 198 colloid after injection into knee.

Thirteen knees were injected with yttrium 90(90Y) ferric hydroxide colloid, and 12 with gold 198(198Au) colloid for treatment of persistent synovitis. Retention in the knee and uptake in lymph nodes and liver were measured by a quantitative scanning technique. There was no significant difference in the retention in the knee of the two different colloids. A tendency towards higher lymph node uptake was observed with 198Au compared with 90y. The inflammatory activity of the knee at the time of treatment may have influenced the subsequent lymph node uptake of 198Au, but not that of the 90Y, nor the overall leakage of either from the knee. 90Yferric hydroxide colloid was retained in the treated knee at least as well as other colloids which have been used for this purpose.

Gold Colloid, Radioactive↗
PubMed2006

[Evaluation of the efficacy of intravenous iron III-hydroxide saccharate for treating adult patients with iron deficiency anemia].

OBJECTIVE: To evaluate the efficacy of intravenous iron III-hydroxide saccharate for treating adult patients with iron deficiency anemia lacking satisfactory response to oral iron therapy. METHODS: Between January 2003 and January 2004, 25 patients with iron deficiency anemia who presented intolerance or inadequate response to iron oral therapy, or hemoglobin level < 7 g/dl were studied. The main laboratory tests performed were: complete blood cell count, reticulocyte count, serum iron, total iron-binding capacity, serum ferritin. Patients received a weekly dose of 200 mg of iron diluted in 250 mL of 0.9% sodium chloride solution administered intravenously for 30 minutes. Treatment continued until a hemoglobin level = 12 g/dL for women and = 13 g/dL for men were obtained or until full administration of the total dose of parenteral iron recommended for each patient. RESULTS: Median age of the patients studied was 45 years (ages ranging from 31 to 70). Nineteen out of 25 patients (76%) were women. The most common cause of iron deficiency anemia was abnormal uterine bleeding observed in 68% of the female patients (13 out of 19) and partial gastrectomy observed in 67% of the male patients (4 out of 6). Seventeen (68%) patients were included in this study because they did not respond to oral iron therapy, 24% (6 out of 25) showed intolerance to oral iron and 8% (2 out of 25) presented hemoglobin level < 7 g/dl. Correction of anemia was obtained in 12 out of 19 female patients (63%) and in 5 out of 6 male patients (83%). The mean hemoglobin and ferritin values were 8.09 g/dl and 4.20 ng/ml (pre-treatment) and 12.42 g/dl and 87.78 ng/ml (post-treatment) (p < 0.001), respectively. The average increase of hemoglobin was 3.74 g/dl, ranging from 1.30 to 7.60 g/dl. None of the patients received blood transfusion during or after the intravenous iron treatment. CONCLUSION: The use of intravenous iron III-hydroxide saccharate is an efficacious and safe option in the treatment of adult patients with iron deficiency anemia lacking satisfactory response to oral iron therapy. This option of treatment should be considered mainly for patients with severe anemia in order to obtain rapid increase of the hemoglobin level and avoid blood transfusion.

Adult↗