An equilibrium analysis of the aqueous H+-MoO4(2-)-(HP)O(3)2- and H+-MoO4(2-)-(HP)O(3)2--HPO4(2-) systems

The speciation in the phosphitomolybdate system, H+-MoO4(2-)-(HP)O(3)2-, has been determined from combined potentiometric and 31P NMR measurements in 0.600 M Na(Cl) medium at 298(1) K. Potentiometric titration data were collected in the ranges 2.5<-log[H+]<6.2, 40.0相似文献   

Syntheses and Characterizations of (4-NH2C6H4S)4Sn and [(4-NH2C6H4S)2(4-NH3C6H4S)2Sn]Cl2

1INTRODUCTIONInrecentyears,theresearchesontinsulfidemateri-alshavedrawnchemists’attentionowningtotheirpo-tentialapplicationsasphotovoltaicmaterials,hologra-phicrecordingsystem[1,,solarcontroldevices[3]and2]semiconductormaterials.Ageneralmethodtopreparetinsulfidesisthechemicalvapourdepositionfromdi-scretesimpletin-sulfidecomplexes,suchas(PhS)4Sn,Sn(SCy)4and[CF3(CF2)5S]4Sn[4].Duringoureffortinsynthesizingtin-sulphurcomplexes[5],weobtainedtwomononucleartincomplexes,(4-NH2C6H4S)4Sn1an…     

NH4VO3在NH4H2PO4-H2O和(NH4)3PO4-H2O体系中的溶解度

采用等温溶解法测定了偏钒酸铵(NH₄VO₃)在NH₄H₂PO₄-H₂O和(NH₄)₃PO₄-H₂O体系中T = 298.15-328.15 K时的溶解度以及溶液的密度和pH值。结果表明, NH₄VO₃的溶解度随着(NH₄)₃PO₄或NH₄H₂PO₄溶液浓度的增大,先降低后升高,这是由于同离子效应、化学反应平衡及离子活度的共同作用。比较T = 298.15K时, NH₄VO₃分别在NH₄H₂PO₄-H₂O、(NH₄)₂HPO₄-H₂O和(NH₄)₃PO₄-H₂O体系中溶解度,发现在相同的磷酸盐浓度下, NH₄VO₃的溶解度在NH₄H₂PO₄-H₂O体系中最大,在(NH₄)₃PO₄-H₂O体系中居中,在(NH₄)₂HPO₄-H₂O体系中最小。进一步地,在T = 298.15 K和磷酸盐浓度C = 0.5 mol·kg^-1时,结合pH值和反应溶度积常数K_SP等计算三个体系中的平均离子活度系数(γ_±),发现γ_±值在(NH₄)₂HPO₄-H₂O体系中最大,在(NH₄)₃PO₄-H₂O体系中居中,在NH₄H₂PO₄-H₂O体系中最小,与溶解度规律一致。     

IR spectrum of the H(5)O(2)(+) cation in the context of proton disolvates L-H(+)-L

The H(5)O(2)(+) ion has been studied in chlorocarbon, benzene, and weakly coordinating anion environments to bridge the gap between the gas-phase and traditional condensed-phase investigations. Symmetrical cations of the type [H(5)O(2)(+) x 4Solv] are formed via H-bonding with the terminal O-H groups. In the infrared spectrum, the nu(s)OH and nu(as)OH vibrations behave in a manner similar to those of common water molecules: the stronger is the H-bonding interaction with the surroundings, the lower is the frequency shift. A consistent pattern of IR bands from the central O-H(+)-O group is identified, regardless of the strength of the interaction of H(5)O(2)(+) with its environment. Three intense bands develop: a (860-995 cm-1), b (1045-1101 cm(-1)), and c (1672-1700 cm(-1)), as well as two weak bands, d ( approximately 1300 cm(-1)) and e ( approximately 1400-1500 cm(-1)). These fingerprint bands are highly characteristic for vibrations of O-H-O group irrespective of formal charge. They are seen in symmetrical proton disolvates of the type L-H(+)-L, where L is an O-atom donor (alcohol, ether, ketone, phosphate, etc.), and in [A-H-A](-) acid salts (A(-) = oxyanion). The commonality is equivalency of the two O-atoms, a short O...O distance (ca. 2.40 Angstrom), and a flat-bottomed potential well for the bridging proton, that is, a short, strong, low-barrier H-bond. Assignments for bands a-e are suggested in an attempt to resolve inconsistencies between experimental and calculated data.     

Infrared spectra of C(3)H(3)(+)-N(2) dimers: identification of proton-bound c-C(3)H(3)(+)-N(2) and H(2)CCCH(+)-N(2) isomers.

Mid-infrared photodissociation spectra of mass selected C(3)H(3)(+)-N(2) ionic complexes are obtained in the vicinity of the C-H stretch fundamentals (2970-3370 cm(-1)). The C(3)H(3)(+)-N(2) dimers are produced in an electron impact cluster ion source by supersonically expanding a gas mixture of allene, N(2), and Ar. Rovibrational analysis of the spectra demonstrates that (at least) two C(3)H(3)(+) isomers are produced in the employed ion source, namely the cyclopropenyl (c-C(3)H(3)(+)) and the propargyl (H(2)CCCH(+)) cations. This observation is the first spectroscopic detection of the important c-C(3)H(3)(+) ion in the gas phase. Both C(3)H(3)(+) cations form intermolecular proton bonds to the N(2) ligand with a linear -C-H...N-N configuration, leading to planar C(3)H(3)(+)-N(2) structures with C(2v) symmetry. The strongest absorption of the H(2)CCCH(+)-N(2) dimer in the spectral range investigated corresponds to the acetylenic C-H stretch fundamental (v(1) = 3139 cm(-1)), which experiences a large red shift upon N(2) complexation (Delta(v1) approximately -180 cm(-1)). For c-C(3)H(3)(+)-N(2), the strongly IR active degenerate antisymmetric stretch vibration (v4)) of c-C(3)H(3)(+) is split into two components upon complexation with N(2): v4)(a(1)) = 3094 cm(-1) and v4)(b(2)) = 3129 cm(-1). These values bracket the yet unknown v4) frequency of free c-C(3)H(3)(+) in the gas phase, which is estimated as 3125 +/- 4 cm(-1) by comparison with theoretical data. Analysis of the nuclear spin statistical weights and A rotational constants of H(2)CCCH(+)-N(2) and c-C(3)H(3)(+)-N(2) provide for the first time high-resolution spectroscopic evidence that H(2)CCCH(+) and c-C(3)H(3)(+) are planar ions with C(2v) and D(3h) symmetry, respectively. Ab initio calculations at the MP2(full)/6-311G(2df,2pd) level confirm the given assignments and predict intermolecular separations of R(e) = 2.1772 and 2.0916 A and binding energies of D(e) = 1227 and 1373 cm(-1) for the H-bound c-C(3)H(3)(+)-N(2) and H(2)CCCH(+)-N(2) dimers, respectively.     

A Study of Crystallization in the System TiO2(Al2O3)-H2SO4-(NH4)2SO4-H2O in Obtaining Titanium-Aluminum Tanning Agent

The conditions under which a titanium-aluminum tanning agent is obtained from sulfuric acid solutions were studied. The composition was established and the properties were studied of the forming phases.     

Raman observation of the interactions between NH4+, SO4(2-), and H2O in supersaturated (NH4)2SO4 droplets

High signal-to-noise ratio (S/N) Raman spectra of (NH(4))(2)SO(4) droplets deposited on a quartz substrate were obtained from dilute to supersaturated states upon decreasing the relative humidity (RH). When the molar water-to-solute ratio (WSR) decreases from 16.8 to 3.2, the v(1)-SO(4)(2-) band changes very little, that is, showing a red-shift of only about 1 cm(-1) (from 979.9 to 978.8 cm(-1)) and an increase of its full width at half-maximum (fwhm) from 8.3 to 9.8 cm(-1). Other vibration modes such as v(2)- and v(4)-SO(4)(2-) bands appear almost constantly at 452 and 615 cm(-1). Such kind of a spectroscopic characteristic is different from previous observation on other cations, indicating that the interactions between SO(4)(2-) and NH(4)+ in supersaturated states are similar to those between SO(4)(2-) and H(2)O in dilute states. After fitting the Raman spectra with Gaussian functions in the spectral range of 2400-4000 cm(-1), we successfully extracted six components at positions of 2878.7, 3032.1, 3115.0, 3248.9, 3468.4, and 3628.8 cm(-1), respectively. The first three components are assigned to the second overtone of NH(4)+ umbrella bending, the combination band of NH(4)+ umbrella bending and rocking vibrations, and the NH(4)+ symmetric stretching vibration, while the latter three components are from the strongly, weakly, and slightly hydrogen-bonded components of water molecules, respectively. With a decrease of the RH, the proportion of the strongly hydrogen-bonded components increases, while that of the weakly hydrogen-bonded components decreases in the droplets. The coexistence of strongly, weakly, and slightly hydrogen-bonded water molecules must hint at a similar hydrogen-bonding network of NH(4)+, SO(4)(2-), and H(2)O to that of pure liquid water in supersaturated (NH(4))(2)SO(4) droplets.     

Single freezing and triple melting of micrometre-scaled (NH4)2SO4/H2O droplets

Atmospheric aerosol droplets containing NH(4)(+) and SO(4)(2-) ions are precursors of cirrus ice clouds. However, the low-temperature phase transformation of such droplets is not understood yet. Here we show for the first time that micrometre-scaled (NH(4))(2)SO(4)/H(2)O droplets produce one freezing event but three melting events which are the melting of (i) pure ice, (ii) eutectic ice/(NH(4))(2)SO(4), and (iii) eutectic ice/(NH(4))(3)H(SO(4))(2). We also find that the melting of ice/(NH(4))(3)H(SO(4))(2) consists of two eutectic melting events, presumably ice/letovicite-II and ice/letovicite-III.     

A hydrothermal investigation of the 1/2V2O5-H2C2O4/H3PO4/NH4OH system: synthesis and structures of (NH4)VOPO(4).1.5H2O, (NH4)0.5VOPO(4).1.5H2O, (NH4)2[VO(H2O)3]2[VO(H2O)][VO(PO4)2](2).3H2O, and (NH4)2[VO(HPO4)]2(C2O4).5H2O

The 1/2V2O5-H2C2O4/H3PO4/NH4OH system was investigated using hydrothermal techniques. Four new phases, (NH4)VOPO(4).1.5H2O (1), (NH4)0.5VOPO(4).1.5H2O (2), (NH4)2[VO(H2O)3]2[VO(H2O)][VO(PO4)2]2.3H2O (3), and (NH4)2[VO(HPO4)]2(C2O4).H2O (4), have been prepared and structurally characterized. Compounds 1 and 2 have layered structures closely related to VOPO(4).2H2O and A0.5VOPO4.yH2O (A = mono- or divalent metals), whereas 3 has a 3D open-framework structure. Compound 4 has a layered structure and contains both oxalate and phosphate anions coordinated to vanadium cations. Crystal data: (NH4)VOPO(4).1.5H2O, tetragonal (I), space group I4/mmm (No. 139), a = 6.3160(5) A, c = 13.540(2) A, Z = 4; (NH4)0.5VOPO(4).1.5H2O, monoclinic, space group P2(1)/m (No. 11), a = 6.9669(6) A, b = 17.663(2) A, c = 8.9304(8) A, beta = 105.347(1) degrees, Z = 8; (NH4)2[VO(H2O)3]2[VO(H2O)][VO(PO4)2]2.3H2O, triclinic, space group P1 (No. 2), a = 10.2523(9) A, b = 12.263(1) A, c = 12.362(1) A, alpha = 69.041(2) degrees, beta = 65.653(2) degrees, gamma = 87.789(2) degrees, Z = 2; (NH4)2[VO(HPO4)]2(C2O4).5H2O, monoclinic (C), space group C2/m (No. 12), a = 17.735(2) A, b = 6.4180(6) A, c = 22.839(2) A, beta = 102.017(2) degrees, Z = 6.     

Structure of the UO2 2+-SO 4 2- ion pair in aqueous solution

The structure of the ion pairs formed in aqueous uranyl sulfate solutions has been investigated with high-energy X-ray scattering. Sulfate binds to the uranyl as a monodentate ligand in equimolar solutions. The geometry of the ion pair is very similar to configurations found in crystalline structures; in particular, the U-O-S angle is bent in solution as well as in the solid state. It can therefore be concluded that an U-O-S angle of 143 degrees is an intrinsic property of the uranyl sulfate bond and not due to packing effects or interaction with the water in the primary solvation shell.     

Theoretical studies of UO2(H2O)n(2+), NpO2(H2O)n(+), and PuO2(H2O)n(2+) complexes (n=4-6) in aqueous solution and gas phase

Extensive ab initio calculations both in gas phase and solution have been carried out to study the equilibrium structure, vibrational frequencies, and bonding characteristics of various actinyl (UO2(2+), NpO2(+), and PuO2(2+)) and their hydrated forms, AnO2(H2O)n(z+) (n=4, 5, and 6). Bulk solvent effects were studied using a continuum method. The geometries were fully optimized at the coupled-cluster singles + doubles (CCSD), density-functional theory (DFT), and M?ller-Plesset (MP2) level of theories. In addition vibrational frequencies have been obtained at the CCSD as well as MP2/DFT levels. The results show that both the short-range and long-range solvent effects are important. The combined discrete-continuum model, in which the ionic solute and the solvent molecules in the first and second solvation shells are treated quantum mechanically while the solvent is simulated by a continuum model, can predict accurately the bonding characteristics. Moreover, our values of solvation free energies suggest that five- and six-coordinations are equally preferred for UO2(2+), and five-coordinated species are preferred for NpO2(+) and PuO2(2+). On the basis of combined quantum-chemical and continuum treatments of the hydrated complexes, we are able to determine the optimal cavity radii for the solvation models. The coupled-cluster computations with large basis sets were employed for the vibrational spectra and equilibrium geometries both of which compare quite favorably with experiment. Our most accurate computations reveal that both five- and six-coordination complexes are important for these species.     

Raman,infrared and force field studies of K2(12)C2O4 x H2O and K2(13)C2O4 x H2O in the solid state and in aqueous solution,and of (NH4)2(12)C2O4 x H2O and (NH4)2(13)C2O4 x H2O in the solid state

The Raman and infrared spectra of solid K2(12)C2O4 x H2O are reported together with, for the first time, the corresponding Raman and infrared spectra of solid K2(13)C2O4 x H2O. Raman spectra of aqueous solutions of both isotopomers are also reported. In the solid state the oxalate anion is planar with D2h symmetry in this salt, whereas in aqueous solution the Raman spectra of the anion are best interpreted on the basis of D2d symmetry. The Raman spectra of solid (NH4)2(12)C2O4 x H2O and (NH4)2(13)C2O4 x H2O, in which the oxalate anion is twisted from planarity by 28 degrees about the CC bond, have also been recorded. Several reassignments have been made. The harmonic force field for the oxalate anion in the D2h, D2 and D2d geometries has been determined in part, and approximate values of key valence force constants determined. All the observed band wavenumbers and 12C/13C isotopic shifts are well reproduced by the force fields. The potential energy distribution of the totally symmetric normal modes of planar oxalate indicates that each mode consists of extensively mixed symmetry corrdinates and that the labels previously used for the bands seen here at 475 and 879 cm(-1) would better be described as v(CC) and deltaS(CO2), respectively, putting them in the same wavenumber order as v(NN) and deltaS(NO2) for the isoelectronic and isostructural molecule N2O4. The stretching force constants of N2O4 and planar C2O4(2-) are established to be in the order f(NN) < f(CC) and f(NO) > f(CO), consistent with the known relative bond lengths.     

Quasi-unary homogeneous nucleation of H2SO4-H2O

We show that the binary homogeneous nucleation (BHN) of H2SO4-H2O can be treated as quasi-unary nucleation of H2SO4 in equilibrium with H2O vapor. A scheme to calculate the evaporation coefficient of H2SO4 molecules from H2SO4-H2O clusters is presented and a kinetic model to simulate the quasi-unary nucleation of H2SO4-H2O is developed. In the kinetic model, the growth and evaporation of sulfuric acid clusters of various sizes are explicitly simulated. The kinetic quasi-unary nucleation model does not have two well-recognized problems associated with the classical BHN theory (violation of the mass action law and mismatch of the cluster distribution for monomers) and is appropriate for the situations where the assumption of equilibrium cluster distribution is invalid. The nucleation rates predicted with our quasi-unary kinetic model are consistent with recent experimental nucleation experiments in all the cases studied, while the most recent version of the classical BHN model systematically overpredicts the nucleation rates. The hydration of sulfuric acid clusters, which is not considered in the classical model but is accounted for implicitly in our kinetic quasi-unary model, is likely to be one of physical mechanisms that lead to lower nucleation rates. Further investigation is needed to understand exactly what cause the difference between the kinetic quasi-unary model and the classical BHN model.     

Speciation in the aqueous H+/H2VO4-/H2O2/phosphate system

The speciation in the aqueous H(+)/H(2)VO(4)(-)/phosphate (dihydrogen phosphate, P(-)) and H(+)/H(2)VO(4)(-)/H(2)O(2)/P(-) systems has been determined in the physiological medium of 0.150 M Na(Cl) at 25 degrees C. A combination of multinuclear NMR integral and chemical shift (Bruker AMX500) as well as potentiometric data (glass electrode) have been collected and treated simultaneously by the computer program LAKE. The pK(a)-values for phosphoric acid have been determined by potentiometric and (31)P NMR chemical shift data, and have been found to be 1.85 +/- 0.02, 6.69 +/- 0.02 and 11.58 +/- 0.07. The errors given are 3sigma. Altogether nine vanadate-phosphate species have been found in the ternary H(+)/H(2)VO(4)(-)/P(-) system in the pH region 1-11, with the following compositions: VP, VP(2) and V(14)P. Equilibrium is very slow in acidic solutions, requiring more than 3 months for the formation of V(14)P species. On the other hand, less than 15 min are needed for equilibration at neutral and alkaline pH. In the quaternary H(+)/H(2)VO(4)(-)/H(2)O(2)/P(-) system, four new species have been found in addition to all binary and ternary complexes. They are of VXP and VX(2)P compositions, where X denotes the peroxo ligand. (51)V and (31)P NMR chemical shifts, compositions and formation constants are given, and equilibrium conditions are illustrated in distribution diagrams as well as the fit of the model to the experimental data. Biological and medical relevance of the species is also discussed and physiological conditions are modelled.     

Crystal Structure and Spectroscopic Studies of a New Organic Dihydrogenmonophosphate [2-NH2-6-CH3-C4H3N2O]2(H2PO4)2

Physicochemical properties of a new dihydrogenmonophosphate [2-NH ₂ -6-CH ₃ -C ₄ H ₃ N ₂ O] ₂ (H ₂ PO ₄ ) ₂ are described on the basis of X-ray crystal structure investigation. This compound crystallizes in the triclinic space group P-1. The unit cell parameters are: a = 7.667(3) Å, b = 8.204(5) Å, c = 14.761(6) Å, α = 98.85(4)°, β = 99.23(3)°, γ = 90.50(4)°, V = 905.0 ų, and Z = 2. The crystal structure was solved and refined to R = 0.037, using 4351 independent reflections. The atomic arrangement of this compound is built up by (H ₂ PO ₄ ) _n ^{n ?} chains. Each chain aggregates with organic molecules to form an open framework architecture through hydrogen bond interactions. The structure includes four types of hydrogen bonds. The first one, O─H─O, links the H ₂ PO ₄ groups to form (H ₂ PO ₄ ) _n ^{n ?} infinite inorganic chains parallel to the a axis. The three other types, O─H─O(carbonylic), N─H─O(carbonylic), and N─H─O, assemble the inorganic chains so as to build up a three-dimensional arrangement. This compound has also been investigated by IR, and solid-state ¹³ C and ³¹ P MAS NMR spectroscopies combined to ab initio calculations.     

Supramolecular stabilization of N(2)H(7)(+)

The cation N(2)H(7)(+) has been stabilized in a largely hydrophobic supramolecular environment and characterized in the solid state. The cation is situated in the bowl-shaped cavity of calix[4]arene. All of the hydrogen atoms are clearly discernible owing to high-quality X-ray data as well as lack of disorder and symmetry-imposed ambiguity. It appears that electrostatic interactions play a critical role in stabilizing the structure.