Presence Of D2 Research Articles

A practical and environmentally friendly protocol for synthesis of α-deuterated carboxylic acids.

α-deuterated carboxylic acids have been synthesized from the corresponding malonic acids via hydrogen/deuterium exchange and decarboxylation in presence of D2 O. The method is general, mild and efficient and does not require organic solvents or other additives. Yields range between 83% and 94% and purification was not necessary. Starting materials were easy accessible and the α-deuterated carboxylic acids may easily be transformed to other labeled compounds such as alcohols, aldehydes, esters, and amides. Characterization with NMR confirmed purity and isotopic purity.

Deuteriodifluoromethylation and gem-Difluoroalkenylation of Aldehydes Using ClCF2 H in Continuous Flow.

The deuteriodifluoromethyl group (CF2 D) represents a challenging functional group due to difficult deuterium incorporation and unavailability of precursor reagents. Herein, we report the use of chlorodifluoromethane (ClCF2 H) gas in the continuous flow deuteriodifluoromethylation and gem-difluoroalkenylation of aldehydes. Mechanistic studies revealed that the difluorinated oxaphosphetane (OPA) intermediate can proceed via alkaline hydrolysis in the presence of D2 O to provide α-deuteriodifluoromethylated benzyl alcohols or undergo a retro [2+2] cycloaddition under thermal conditions to provide the gem-difluoroalkenylated product.

Ablation of tungsten surfaces in collisions with Ar+, He+ and N2+ cation projectiles in the presence of D2

Surface ablation of tungsten, known as a plasma-facing material in fusion devices, was investigated mass-spectrometrically in ion beam-type experiments by exposing a tungsten surface in the presence of H2/D2 to fast atomic and molecular projectile ions with high electron-recombination energies (Ar+, He+ and N2+). The sputtered product ions were monitored by high resolution mass spectrometry, in the case of Ar+, at various beam energies, surface temperatures and partial pressures of D2 at beam and product-ion angles of 45°. Bare monatomic and diatomic tungsten ions were seen to be sputtered, more so at elevated ion impact energies and increasing surface temperatures. The relative yield of deuterated WD+ ions was enhanced at higher impact energies and increased partial pressures of D2, but diminished with increasing tungsten temperature. Overall, the observations under our experimental conditions suggest the occurrence of Physical Sputtering (PS) of bare tungsten ions, W+ and W2+, as well as Chemically Assisted Physical Sputtering (CAPS) of WD+ with concomitant dissociation of D2.

Effect of divalent cation addition on structure, conductivity and grain boundary properties in La doped ceria oxygen ion conductors

The aim of this work is to investigate the effect of divalent cations on the structure and electrical properties of Ce0.85La0.1D0.05O2-δ (D = Ca, Sr and Ba) oxygen ion conductors. The X-Ray structural analysis confirms the presence of CeDO3 minor phase in addition to cubic fluorite phase of ceria in Sr2+ and Ba2+ added compositions. The lattice parameter of the compositions significantly depends on the ionic radius of dopants and the presence of D2+ ions in ceria lattice. The Ca2+ added composition shows the highest free oxygen vacancy concentration due to its lowest association energy and complete dissolution of Ca2+ ions into ceria lattice. The dopant-vacancy association energy and grain interior conductivity changes with the ionic radii of the divalent dopants. The grain boundary capacitance depends on dielectric constant, grain size and grain boundary thickness. The grain boundary conductivity shows 46% over total conductivity for Sr2+ added composition. The presence of CeDO3 phase and space charge layer promotes the grain boundary resistances and affects the ion dynamics. Schematic models are proposed to understand the ion migration in grain boundaries. The scavenging effect is found to be highest in Sr2+ ions added composition. The defect structures, the presence of CeDO3 phase and electrical properties are correlated with each other.

Proton-Coupled Electron-Transfer Processes in Ultrafast Time Domain: Evidence for Effects of Hydrogen-Bond Stabilization on Photoinduced Electron Transfer.

The proton-coupled electron-transfer (PCET) reaction is investigated for a newly synthesized imidazole-anthraquinone biomimetic model with a photoactive RuII -polypyridyl moiety that is covalently coupled to the imidazole fragment. Intramolecular H-bonding interactions between imidazole and anthraquinone moieties favor the PCET process; this can be correlated to an appreciable positive shift in the one-electron reduction potential of the coordinated anthraquinone moiety functionalized with the imidazole fragment. This can also be attributed to the low luminescence quantum yield of the RuII -polypyridyl complex used. The dynamics of the intramolecular electron-transfer (ET) and PCET processes are studied by using femtosecond transient absorption spectroscopy. The steady-state spectroscopic studies and the results of the time-resolved absorption studies confirm that H-bonded water molecules play a major role in both ET and PCET dynamics as a proton relay in the excited state. The electron-transfer process is followed by a change in the H-bonding equilibrium between AQ and imidazole in acetonitrile solvent, and protonation of AQ.- by water leads to PCET in the presence of water. A slower forward and backward electron-transfer rate is observed in the presence of D2 O compared with that in H2 O. These results provide further experimental support for a detailed understanding of the PCET process.

Comparison of two methods for measuring 25-OH vitamin D in the follow-up of patients after bilio-pancreatic diversion bariatric surgery

ObjectiveOur objective was to compare the ECLIA from Roche versus the LC–MS/MS method for quantitation of serum 25-hydroxy-vitamin D in patients who have undergone bariatric surgery. Design and methodsCross-sectional and correlational studies were performed on three different groups for the 25-OH-D levels quantitated by both methods. The control group of apparently healthy subjects was randomly selected in a clinical chemistry laboratory. Test groups were patients who had undergone bilio-pancreatic diversion (BPD) and were supplemented either with vitamin D2 or with vitamin D3. The number of samples per group was established according to the CLSI recommendation protocol (EPO9-A2-IR). ResultsThe agreement of LC-MS/MS with the Roche method was acceptable in the apparently healthy subjects group and in the post-BPD D3-supplemented group with an average bias of −1.7% and −9.2%, respectively. However, this agreement was unacceptable in the post-BPD D2-supplemented group with an average bias of −45.3%. The LC–MS/MS enabled us to detect four patients who had excess vitamin D or poisoning with vitamin D for which it was necessary to stop the supplementation with vitamin D in the D2 -supplemented group. ConclusionDespite the apparent good agreement between the Roche method and LC–MS/MS in the healthy subjects group and in the post-DBP D3-supplemented patient group, a considerable bias seems to exist, particularly in the presence of D2. The LC–MS/MS method is therefore the most accurate method to follow the vitamin D2 -supplemented bariatric population.

Effect of the aspartic acid D2 on the affinity of Polybia-MP1 to anionic lipid vesicles

Polybia-MP1 (IDWKKLLDAAKQIL-NH2), a helical peptide extracted from the venom of a Brazilian wasp, has broad-spectrum antimicrobial activities without being hemolytic or cytotoxic. This peptide has also displayed anticancer activity against cancer cell cultures. Despite its high selectivity, MP1 has an unusual low net charge (Q = +2). The aspartic residue (D2) in the N-terminal region plays an important role in its affinity and selectivity; its substitution by asparagine (D2N mutant) led to a less selective peptide. Aiming to explore the importance of this residue for the peptides' affinity, we compared the zwitterionic and anionic vesicle adsorption activity of Polybia-MP1 versus its D2N mutant and also mastoparan X (MPX). The adsorption, electrostatic, and conformational free energies were assessed by circular dichroism (CD) and fluorescence titrations using large unilamellar vesicles (LUVs) at the same conditions in association with measurement of the zeta potential of LUVs in the presence of the peptides. The adsorption free energies of the peptides, determined from the partition coefficients, indicated higher affinity of MP1 to anionic vesicles compared with the D2N mutant and MPX. The electrostatic and conformational free energies of MP1 in anionic vesicles are less favorable than those found for the D2N mutant and MPX. Therefore, the highest affinity of MP1 to anionic vesicles is likely due to other energetic contributions. The presence of D2 in MP1 makes these energetic components 1.2 and 1.5 kcal/mol more favorable compared with the D2N mutant and MPX, respectively.

Characterization of an unusual bipolar helicase encoded by bacteriophage T5

Bacteriophage T5 has a 120 kb double-stranded linear DNA genome encoding most of the genes required for its own replication. This lytic bacteriophage has a burst size of ∼500 new phage particles per infected cell, demonstrating that it is able to turn each infected bacterium into a highly efficient DNA manufacturing machine. To begin to understand DNA replication in this prodigious bacteriophage, we have characterized a putative helicase encoded by gene D2. We show that bacteriophage T5 D2 protein is the first viral helicase to be described with bipolar DNA unwinding activities that require the same core catalytic residues for unwinding in either direction. However, unwinding of partially single- and double-stranded DNA test substrates in the 3′–5′ direction is more robust and can be distinguished from the 5′–3′ activity by a number of features including helicase complex stability, salt sensitivity and the length of single-stranded DNA overhang required for initiation of helicase action. The presence of D2 in an early gene cluster, the identification of a putative helix-turn-helix DNA-binding motif outside the helicase core and homology with known eukaryotic and prokaryotic replication initiators suggest an involvement for this unusual helicase in DNA replication initiation.

State of titanium in supported titanium-magnesium catalysts for propylene polymerization

The oxidation state of titanium and the coordination state of Ti3+ ions in TiCl4/D1/MgCl2 (D1 is a phthalate) supported titanium-magnesium catalysts (TMCs) after the interaction with an AlEt3/D2 cocatalyst (D2 is propyltrimethoxysilane or dicyclopentyldimethoxysilane) were studied by chemical analysis and EPR spectroscopy. Different oxidation state distributions of titanium ions were observed in the activated catalyst and mother liquor: Ti3+ and Ti2+ ions were predominant in the activated catalyst and mother liquor, respectively. The effects of interaction conditions (reaction temperature and time and Al/Ti and D2/Ti molar ratios) of TMCs with the cocatalyst on the state of titanium in activated samples were studied. The interaction of TMCs with the cocatalyst decreased the titanium content and caused the appearance of aluminum in the activated sample, which was most clearly pronounced at a temperature of 25°C and occurred within the first 10 min of treatment. An increase in the temperature to 70°C and an increase in the interaction time to 60 min only slightly affected the concentrations of titanium and aluminum. The presence of D2 as a cocatalyst constituent facilitated the removal of titanium compounds and restricted the adsorption of aluminum compounds on the catalyst surface. The main fraction of titanium consisted of Ti3+ ions (62–89%), and the rest was Ti4+ ions (22–35%) under mild interaction conditions (25°C; Si/Ti = 25) or Ti4+ (0–21%) and Ti2+ (9–21%) ions under more severe conditions (50 or 70°C; Si/Ti from 0 to 5). According to EPR-spectroscopic data, at D2/Ti from 1 to 5, Ti3+ ions mainly occurred as associates, whereas they occurred as isolated ions at D2/Ti = 25. The initial and activated catalysts were similar in activity in the reaction of propylene polymerization, and titanium compounds, which were removed from the catalyst upon interaction with AlEt3/D2, were inactive in this process.

Reactivity studies on [Cp′FeI]2: From iron hydrides to P4-activation

Metathesis of [Cp′FeI]2 (1) with KHBEt3 affords the polyhydride iron complexes [Cp′FeH2]2 (2) and [Cp′2Fe2H3] (3). The ratio in which both 2 and 3 are obtained correlates to the applied H2 pressure during synthesis. Complex 2 activates CH- or CD- bonds in aromatic compounds and shows slow H/D exchange in the presence of D2 at room temperature in cyclohexane solvent. [Cp′FeH2]2 acts as a Cp′Fe(I)-synthon when reacted with white phosphorus (P4) to give [Cp′Fe]2(μ-P4) (4) as the only P-containing product. This complex is best described as a triple-decker complex with a planar arrangement of a severely distorted kite-like cyclo-P4 unit. This distortion persists in solution and solid state as evidenced by a small PP coupling constant in the 31P{1H} NMR spectrum and a long P–P distance of 2.53 A. Complex 4 is an isomer to the long-known [{Cp′Fe}2(μ-η4:η4-P4)] (5) with a cis-tetraphosphabutadiene moiety and it thermally rearranges to 5, [{Cp′Fe}2(μ-η3:η3-P3)] and [Cp′Fe(P5)]. All complexes described in this paper have been completely characterized including X-ray crystallography, variable temperature NMR studies and DFT calculations. Relaxed force constants (inverse compliance constants) are used as bond strength descriptors.

Stereochemistry and the use of H2/D2 mixtures as probes into the mechanism of hydrogenations catalyzed by cationic rhodium (DIPHOS) complexes

The stereochemistry of the hydrogenation of 4-tert-butylmethylenecyclohexane (1) and the use of D2 or D2/H2 mixtures in place of H2 furnishes evidence that hydrogenations using the catalyst precursor [Rh(DIPHOS)(COD)]+BF4− proceed via more than one mechanism. This evidence includes the effect of changes in pressure and added triethylamine upon the kinetics and isomerization of 1, as well as the distribution of the added deuterium in the products of the reaction of 1 or norbornene with either D2 or H2/D2 mixtures. That an alkene necessarily causes the equilibration of H2/D2 mixtures, although it need not involve any of the alkenes’s hydrogen atoms (e.g., norbornene), provides a clue to the process by which the mononuclear mechanism proposed by Halpern, which is dominant near one atmosphere of H2, merges into another with increasing pressure. It has been proposed that the cationic complex [Rh(DIPHOS)S2]+ is transformed in the presence of an alkene and hydrogen into a binuclear hydrido complex, such as those described by Sivak and Muetterties (1979) and Fryzuk (1982), which represent a far more active catalyst than its mononuclear precursor. Such an intermediate should readily catalyze the H2-D2 equilibration and the isomerization of an alkene in the presence of D2 without necessarily introducing deuterium into the product.

Sustained photoevolution of molecular hydrogen in a mutant of Synechocystis sp. strain PCC 6803 deficient in the type I NADPH-dehydrogenase complex.

The interaction between hydrogen metabolism, respiration, and photosynthesis was studied in vivo in whole cells of Synechocystis sp. strain PCC 6803 by continuously monitoring the changes in gas concentrations (H2, CO2, and O2) with an online mass spectrometer. The in vivo activity of the bidirectional [NiFe]hydrogenase [H2:NAD(P) oxidoreductase], encoded by the hoxEFUYH genes, was also measured independently by the proton-deuterium (H-D) exchange reaction in the presence of D2. This technique allowed us to demonstrate that the hydrogenase was insensitive to light, was reversibly inactivated by O2, and could be quickly reactivated by NADH or NADPH (+H2). H2 was evolved by cells incubated anaerobically in the dark, after an adaptation period. This dark H2 evolution was enhanced by exogenously added glucose and resulted from the oxidation of NAD(P)H produced by fermentation reactions. Upon illumination, a short (less than 30-s) burst of H2 output was observed, followed by rapid H2 uptake and a concomitant decrease in CO2 concentration in the cyanobacterial cell suspension. Uptake of both H2 and CO2 was linked to photosynthetic electron transport in the thylakoids. In the ndhB mutant M55, which is defective in the type I NADPH-dehydrogenase complex (NDH-1) and produces only low amounts of O2 in the light, H2 uptake was negligible during dark-to-light transitions, allowing several minutes of continuous H2 production. A sustained rate of photoevolution of H2 corresponding to 6 micro mol of H2 mg of chlorophyll(-1) h(-1) or 2 ml of H2 liter(-1) h(-1) was observed over a longer time period in the presence of glucose and was slightly enhanced by the addition of the O2 scavenger glucose oxidase. By the use of the inhibitors DCMU [3-(3,4-dichlorophenyl)-1,1-dimethylurea] and DBMIB (2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone), it was shown that two pathways of electron supply for H2 production operate in M55, namely photolysis of water at the level of photosystem II and carbohydrate-mediated reduction of the plastoquinone pool.

Dimerization in vivo and inhibition of the nonreceptor form of protein tyrosine phosphatase epsilon.

cyt-PTP epsilon is a naturally occurring nonreceptor form of the receptor-type protein tyrosine phosphatase (PTP) epsilon. As such, cyt-PTP epsilon enables analysis of phosphatase regulation in the absence of extracellular domains, which participate in dimerization and inactivation of the receptor-type phosphatases receptor-type protein tyrosine phosphatase alpha (RPTPalpha) and CD45. Using immunoprecipitation and gel filtration, we show that cyt-PTP epsilon forms dimers and higher-order associations in vivo, the first such demonstration among nonreceptor phosphatases. Although cyt-PTP epsilon readily dimerizes in the absence of exogenous stabilization, dimerization is increased by oxidative stress. Epidermal growth factor receptor stimulation can affect cyt-PTP epsilon dimerization and tyrosine phosphorylation in either direction, suggesting that cell surface receptors can relay extracellular signals to cyt-PTP epsilon, which lacks extracellular domains of its own. The inactive, membrane-distal (D2) phosphatase domain of cyt-PTP epsilon is a major contributor to intermolecular binding and strongly interacts in a homotypic manner; the presence of D2 and the interactions that it mediates inhibit cyt-PTP epsilon activity. Intermolecular binding is inhibited by the extreme C and N termini of D2. cyt-PTP epsilon lacking these regions constitutively dimerizes, and its activities in vitro towards para-nitrophenylphosphate and in vivo towards the Kv2.1 potassium channel are markedly reduced. We conclude that physiological signals can regulate dimerization and phosphorylation of cyt-PTP epsilon in the absence of direct interaction between the PTP and extracellular molecules. Furthermore, dimerization can be mediated by the D2 domain and does not strictly require the presence of PTP extracellular domains.

Synthesis of Isotopically Labeled (E)-β,γ-Unsaturated Esters with Total or High Diastereoselectivity by Using Samarium Diiodide.

A simple, efficient, highly diastereoselective method for preparing (E)-α,δ-dideuterio-β,γ-unsaturated esters: SmI2 -promoted reduction/elimination of α-halo-β-hydroxy-γ,δ-unsaturated esters in the presence of D2 O. This provides the desired products in which the C-C double bond is generated with total or high diastereoselectivity.

Reactivity of Site-Isolated Metal Clusters: Propylidyne on γ-Al2O3-Supported Ir4

To contrast the reactivity of supported metal clusters with that of extended metal surfaces, we investigated the reactions of tetrairidium clusters supported on porous gamma-Al2O3 (Ir4/gamma-Al2O3) with propene and with H2. Infrared, 13C NMR, and extended X-ray absorption fine-structure spectroscopy were used to characterize the ligands formed on the clusters. Propene adsorption onto Ir4/gamma-Al2O3 at 298 K gave stable, cluster-bound mu3-propylidyne. Propene adsorbed onto Ir4/gamma-Al2O3 at 138 K reacted at approximately 219 K to form a stable, highly dehydrogenated, cluster-bound hydrocarbon species approximated as CxHy (such as, for example, C3H2 or C2H). H2 reacted with Ir4/gamma-Al2O3 at 298 K, forming ligands (likely hydrides), which prevented subsequent reaction of the clusters with propene to form propylidyne. Propylidyne on Ir4 was stable in helium or H2 as the sample was heated to 523 K, whereupon it reacted with oxygen of the support to give CO. Propylidyne on Ir4 did not undergo isotopic exchange in the presence of D2 at 298 K. In contrast, the literature shows that propylidyne chemisorbed on extended metal surfaces is hydrogenated in the presence of H2 (or D2) and exchanges hydrogen with gaseous D2 at room temperature; in the absence of H2, it decomposes thermally to give hydrocarbon fragments at temperatures much less than 523 K. The striking difference in reactivities of propylidyne on clusters and propylidyne on extended metal surfaces implies the requirement of ensembles of more than the three metal surface atoms bonded to propylidyne in the surface reactions. The results highlight the unique reactivity of small site-isolated metal clusters.

Changes in the hydrogenative ring-opening mechanism of cyclohexene oxide over Cu/SiO2 resulting from the addition of cyclohexene, a major product

The ring-opening mechanism influencing effect of a major product in the cyclohexene oxide–D2 system was investigated over a Cu/SiO2 catalyst. This product is cyclohexene, thus, the hydrogenative ring opening of a 1:1 cyclohexene oxide–cyclohexene mixture was studied in the presence of D2 at 403 K in a closed circulation reactor. It was found that the mechanism of single C–O scission was not affected, but that of the double C–O scission was changed. Simultaneous bond cleavage was the major route of ring opening in the additive-free system and it became consecutive on cyclohexene addition. Added cyclohexene was hydrogenated with a very low rate, but it transformed the surface of the catalyst and, thus, facilitated the change in the mechanism. An explanation concerning the seemingly anomalous lack of deuterium in a product (cyclohexane) not seen in the additive-free system is also suggested.

Effect of nicotine on type 2 deiodinase activity in cultured rat glial cells.

Intracellular generation of triiodothyronine (T3) from thyroxine (T4) by type 2 deiodinase (D2) in the mammalian brain, plays a key role in thyroid hormone action. The presence of D2 in rat astrocytes suggests the importance of glial cells in the regulation of intracellular T3 levels in the rat central nervous system (CNS). To analyze further the factors that regulate D2 activity in the CNS, we investigated the effects of nicotine and of mecamylamine, which inhibits the binding of nicotine with nicotinic acetylcholine receptors, on D2 activity in cultured mixed glial cells of the rat brain. We incubated cultured mixed glial cells obtained from neonatal Wistar rats in the presence of 10 mM dithiothreitol, 2 nM [125I] reverse T3 and 1 mM 6-N-propyl-2-thiouracil for 2 h at 37 degrees C, and the released 125I- was counted in a gamma counter. D2 activity of cultured cells was dependent on the temperature and the amount of protein. The basal D2 activity of rat mixed glial cells was 1.9 +/- 0.2 fmol of I- released/mg protein/h (mean +/- SEM). The addition of 10(-11), 2 x 10(-11), 10(-10), and 10(-9) M nicotine significantly increased D2 activity to approximately 2.2-, 2.4, 3.5- and 2.9-fold the basal level, respectively. D2 activity stimulated by 10(-8) M nicotine (2.5-fold) reached a peak after 9 h incubation. The stimulatory effect of nicotine was completely blocked by 10(-6) M mecamylamine. In conclusion, nicotine increases D2 activity probably via nicotinic acetylcholine receptors, and may influence brain function, at least in part, by affecting thyroid hormone metabolism.

The influence of copper on the effect of certain surfactants during the cementation of cadmium by suspended zinc particles

The influence of copper on the effect of nonylphenolpolyethylene glycol (D1), dinaphthylmethane-4,4′-disulphonic acid (D2) and polyethylene glycol with molecular weight 400 (D3) during cadmium–zinc dust cementation was investigated. The behaviour of D1, D2 and D3 was determined by comparing the results obtained with and without surfactant. It was found that in the presence of copper D1 improves, but D2 and D3 inhibit cadmium cementation. The presence of copper substantially changes the effect of D1 and D3 which becomes opposite to the effect of these surfactants in the absence of copper. The addition of copper has no effect on the influence of D2. SEM study of cementation products indicates a change of deposit structure in the presence of copper. The addition of copper causes the formation of coarser deposits. Morphology of cementation products changes from a completely compact layer in the presence of D1 to a porous layer in the presence of both copper and D1 which corresponds to the cementation kinetics results. The addition of copper enhances dendrite formation in the presence of D2 and contributes to the formation of clusters in the presence of D3. Dendrite formation in the presence of D2 probably increases hydrogen evolution which inhibits cadmium deposition. The addition of D1 to the zinc sulphate solution containing copper and cadmium increases co-deposition of these impurities during the cementation by suspended zinc particles.

The effect of certain surfactants on the cementation of cadmium by suspended zinc particles

The effect of the surfactants nonylphenolpolyethylene glycol (D1), dinaphthylmethane-4,4′-disulphonic acid (D2) and polyethylene glycol with molecular weight 400 (D3) on cadmium-zinc dust cementation kinetics as well as on cadmium deposit structure was investigated. The behaviour of each surfactant was determined by comparing the results obtained with and without surfactant. The reaction of cadmium cementation follows first-order kinetics in the presence of and without surfactants. Additions D1 and D2 decrease but D3 increases the rate of cadmium deposition. Highest inhibition effect on the cementation rate was found in the presence of D1. The increase of cadmium deposition in the presence of D3 probably corresponds to the inhibition of hydrogen evolution due to the addition of this surfactant. SEM study of cadmium deposits showed the formation of a uniform layer of cadmium on the zinc particles surface in the presence of D1 and D3 as well as the formation of many dendrites in the presence of D2. The lowest deposit porosity is observed in the presence of D1 which correlates with the high inhibition effect of this surfactant on cadmium cementation rate. Dendrite formation in the presence of D2 probably increases hydrogen evolution which is in accordance with the obtained inhibition effect of D2 on cadmium cementation. Cadmium deposited in the presence of D3 forms a layer with a high porosity.

Mechanism of the reduction of molecular nitrogen to hydrazine by niobium (iii) hydroxide

The effect of the concentration of water on the rate of reduction of molecular nitrogen to hydrazine by niobium(iii) hydroxide in alkaline H2O−MeOH and D2O−MeOD mixtures was studied. In both cases, the reaction rate is maximum when [H2O]=4 mol L−1, and the inverse isotopic effect (KD/kH>1) is observed when [H2O]<20 mol L−1. Similar regularity was observed for the reaction of hydrogen elimination. It was found that HD is formed in the H2O−MeOH system in the presence of D2. The conclusion was made that the ratedetermining stage in hydrazine formation is the transfer of a hydride ion to the dinitrogen molecule coordinated to the binuclear NbIII center. A kinetic scheme satisfactorily explaining the effect of the concentration of water ([H2O]=1.5−49.0 mol L−1) on the reaction rate constant was proposed.