Chemical data evaluation: general considerations and approaches for IUPAC projects and the chemistry community (IUPAC Technical Report).

The International Union of Pure and Applied Chemistry (IUPAC) has a long tradition of supporting the compilation of chemical data and their evaluation through direct projects, nomenclature and terminology work, and partnerships with international scientific bodies, government agencies and other organizations. The IUPAC Interdivisional Subcommittee on Critical Evaluation of Data (ISCED) has been established to provide guidance on issues related to the evaluation of chemical data. In this first report we define the general principles of the evaluation of scientific data and describe best practices and approaches to data evaluation in chemistry.

Reference Materials for Phase Equilibrium Studies. 1. Liquid-Liquid Equilibria (IUPAC Technical Report).

This article is the first of three projected IUPAC Technical Reports resulting from IUPAC Project 2011-037-2-100 (Reference Materials for Phase Equilibrium Studies). The goal of that project was to select reference systems with critically evaluated property values for the validation of instruments and techniques used in phase equilibrium studies for mixtures. This Report proposes seven systems for liquid-liquid equilibrium studies, covering the four most common categories of binary mixtures: aqueous systems of moderate solubility, non-aqueous systems, systems with low solubility, and systems with ionic liquids. For each system, the available literature sources, accepted data, smoothing equations, and estimated uncertainties are given.

Spectroscopic Study of the Behavior of Mo(VI) and W(VI) Polyanions in Sulfuric-Phosphoric Acid Mixtures.

The solution chemistry of Mo(VI) and W(VI) in mixtures of sulfuric and phosphoric acids is relevant to the development of practicable hydrometallurgical processes for the recovery and separation of these two elements from low-grade scheelite ores. The behavior of Mo(VI) and W(VI) in such mixtures has been studied using X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), nuclear magnetic resonance (NMR), and small-angle X-ray scattering (SAXS) spectroscopies, along with electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS). Where applicable, these techniques have produced a self-consistent picture of the similarities and differences between the chemical speciation of Mo(VI) and W(VI) as functions of solution composition, mostly at a constant phosphorous/metal (P/M; M = Mo(VI) or W(VI)) ratio of ∼1. In dilute acidic media (0.02 mol·kg-1 H+, without H2SO4), Mo(VI) exists mostly (∼60%) as P2Mo5O236- with the remaining ∼40% as ß-Mo8O264-. Under the same conditions, W(VI) is largely present as NaPW11O396- (∼80%) and P2W5O236- (∼10%), with the remainder probably occurring as isopolytungstates such as W12O4212- and some tungstophosphate dimers such as P2W18O626-. At higher acid concentrations (≲5 mol·kg-1 H2SO4), polymeric Mo(VI) anions are broken down to form the oxocations MoO22+ and Mo2O52+ and their protonated forms, with the dimers becoming increasingly dominant at higher acidities (∼80% in 5 mol·kg-1 H2SO4). In stark contrast, W(VI) polyanions do not decompose at higher acidities but instead form (∼70% in 0.6 mol·kg-1 H2SO4) a Keggin ion, PW12O403-. Further acidification with H2SO4 results in the agglomeration of this Keggin ion, forming clusters of about 50 and 100 Å in diameter that ultimately produce crystalline precipitates, which could be identified in part by their X-ray diffraction patterns. Possible application of these findings to the hydrometallurgical separation of Mo and W using acidic solutions is briefly discussed, based on a limited number of batch solvent extractions.

A spectroscopic study of solvent effects on the formation of Cu(ii)-chloride complexes in aqueous solution.

A combination of electronic (UV-vis) and X-ray absorption (EXAFS, XANES) spectroscopies has been used to investigate the formation of copper(ii)/chloride complexes in concentrated aqueous solutions. It is established that lowering the water activity by the addition of Mg(ClO4)2 at a constant Cl-/Cu(ii) ratio results in the replacement of water molecules by Cl- ions in the primary coordination shell of Cu(ii). This behavior closely parallels the effect of increasing the Cl-/Cu(ii) ratio and demonstrates that full understanding of the stoichiometry and structures of the complexes formed in concentrated metal-ion chloride solutions requires explicit consideration of the role of the solvent.

The Fate of Morbidly Obese Patients With Joint Pain: A Retrospective Study of Patient Outcomes.

BACKGROUND: The number of obese patients seeking a total joint arthroplasty (TJA) continues to increase. Weight loss is often recommended to treat joint pain and reduce risks associated with TJA. We sought to determine the effectiveness of an orthopedic surgeon's recommendation to lose weight. METHODS: We identified morbidly obese (body mass index (BMI) 40-49.9 kg/m2) and super obese (BMI ≥50 kg/m2) patients with hip or knee osteoarthritis. Patients with less than 3-month follow-up were excluded. Patient characteristics (age, gender, BMI, comorbidities), disease characteristics (joint affected, radiographic osteoarthritis grading), and treatments were recorded. Clinically meaningful weight loss was defined as weight loss greater than 5%. RESULTS: Two hundred thirty morbid and 50 super obese patients were identified. Super obese patients were more likely to be referred to weight management (52.0% vs 21.7%, P < .001) and were less likely to receive TJA (20.0% vs 41.7%, P = .004). Each 1 kg/m2 increase in BMI decreased the odds of TJA by 10.9% (odds ratio = 0.891, 95% confidence interval: 0.833-0.953, P = .001). Forty (23.0%) of the nonoperatively treated patients achieved clinically meaningful weight loss, and 19 (17.9%) patients who underwent TJA lost weight before surgery. After surgery, the number of patients who achieved a clinically meaningful weight loss grew to 32 (30.2%). CONCLUSION: In morbid and super obese patients, increasing BMI reduces the likelihood that a patient will receive TJA, and when counseled by their orthopedic surgeon, few patients participate in weight-loss programs or are otherwise able to lose weight. Weight loss is an inconsistently modifiable risk factor for joint replacement surgery.

Hydration and ion association of La3+ and Eu3+ salts in aqueous solution.

Aqueous solutions of five lanthanide salts: LaCl3, La(NO3)3, La2(SO4)3, Eu(NO3)3 and Eu2(SO4)3 have been studied at 25 °C by dielectric relaxation spectroscopy over the frequency range 0.05 ≤ ν/GHz ≤ 89. Detailed analysis of the solvent-related modes located at higher frequencies showed that both La3+ and Eu3+ are strongly hydrated, even including partial formation of a third hydration shell similar to that of Al3+(aq). Up to two solute-related modes could be detected at lower frequencies, due to the formation of various types of 1 : 1 ion pairs (IPs). All five salts showed modest levels of association in the order Cl- < NO3- ≪ SO42-, mostly in the form of double-solvent-separated IPs with small amounts of solvent-shared IPs. Overall association constants, , calculated from the stepwise IP formation constants were consistent with literature values.

Association of ionic liquids in solution: a combined dielectric and conductivity study of [bmim][Cl] in water and in acetonitrile.

Ion association of the ionic liquid [bmim][Cl] in acetonitrile and in water was studied by dielectric spectroscopy for salt concentrations c ≤ 1.3 M at 298.15 K and by measurement of molar electrical conductivities, Λ, of dilute solutions (c ≤ 0.006 M) in the temperature range 273.15 ≲ T/K ≤ 313.15. Whilst acetonitrile solutions of [bmim][Cl] exhibit moderate ion pairing, with an association constant of K°(A) ≈ 60 M(-1) and increasing with temperature, [bmim][Cl] is only weakly associated in water (K°(A) ≈ 6 M(-1)) and ion pairing decreases with rising temperature. Only contact ion pairs were detected in both solvents. Standard-state enthalpy, entropy and heat capacity changes of ion association were derived, as well as the activation enthalpy of charge transport and the limiting conductivity of the cation, λ(∞) ([bmim](+)). These data, in conjunction with effective solvation numbers obtained from the dielectric spectra, suggest that the solvation of [bmim](+) is much weaker in water than in acetonitrile.

Dynamics of imidazolium ionic liquids from a combined dielectric relaxation and optical Kerr effect study: evidence for mesoscopic aggregation.

We have measured the intermolecular dynamics of the 1,3-dialkylimidazolium-based room-temperature ionic liquids (RTILs) [emim][BF(4)], [emim][DCA], and [bmim][DCA] at 25 degrees C from below 1 GHz to 10 THz by ultrafast optical Kerr effect (OKE) spectroscopy and dielectric relaxation spectroscopy (DRS) augmented by time-domain terahertz and far-infrared FTIR spectroscopy. This concerted approach allows a more detailed analysis to be made of the relatively featureless terahertz region, where the higher frequency diffusional modes are strongly overlapped with librations and intermolecular vibrations. Of greatest interest though, is an intense low frequency (sub-alpha) relaxation that we show is in accordance with recent simulations that have reported mesoscopic structure arising from aggregates or clusters--structure that explains the anomalous and inconveniently high viscosities of these liquids.

Temperature dependence of the dielectric properties and dynamics of ionic liquids.

Dielectric spectra were measured for eight, mostly imidazolium-based, room temperature ionic liquids (RTILs) over a wide range of frequencies (0.2 < or = nu/GHz < or = 89) and temperatures (5 < or = theta/degrees C < or = 65). Detailed analysis of the spectra shows that the dominant low frequency process centred at ca. 0.06 to 10 GHz (depending on the salt and the temperature) is better described using a symmetrically broadened Cole-Cole model rather than the asymmetric Cole-Davidson models used previously. Evaluation of the temperature dependence of the static permittivities, effective dipole moments, volumes of rotation, activation energies, and relaxation times derived from the dielectric data indicates that the low frequency process cannot be solely due to rotational diffusion of the dipolar imidazolium cations, as has been thought, but must also include other contributions, probably from cooperative motions. Analysis of the Debye process observed at higher frequencies for these RTILs is not undertaken because it overlaps with even faster processes that lie outside the range of the present instrumentation.

Dipole correlations in the ionic liquid 1-N-ethyl-3-N-methylimidazolium ethylsulfate and its binary mixtures with dichloromethane.

Dielectric spectra over the frequency range of 0.2 less, similar nu/GHz < or = 89 have been measured for the room-temperature ionic liquid 1-N-ethyl-3-N-methylimidazolium ethylsulfate ([emim][EtSO(4)], IL) and its mixtures with dichloromethane (DCM) at temperatures of 5 < or = vartheta/ degrees C < or = 65 and 25 degrees C respectively. The spectra of the neat IL at all temperatures and those of the mixtures could be satisfactorily fitted by assuming three relaxation modes, a Cole-Cole process at lower frequencies and two Debye processes at higher frequencies. Consistent with previous studies, detailed analysis of the first (lowest-frequency) process, centered at 0.2-2 GHz depending on temperature and composition, indicated that it is mainly due to the reorientation of the dipolar [emim](+) cations. At high dilutions in the mixtures (x(IL) less, similar 0.2), contact ion pairs also contribute to this mode. The second mode at approximately 8 GHz, which is absent from the dielectric spectra of previously studied imidazolium salts and their mixtures with DCM, is assigned to reorientation of the dipolar [EtSO(4)](-) anions. The highest-frequency mode (located at approximately 80 GHz) in the mixtures is a composite of low-energy intermolecular vibrations originating from the IL and the rotational diffusion of DCM molecules. Detailed analysis of the spectra reveals marked orientational correlations of the IL components, with the cation dipoles showing a strong preference for parallel and the anions showing preference for antiparallel arrangements. These effects are the probable cause of the unusually high dielectric constant of [emim][EtSO(4)]. The structure of the IL appears to be maintained up to quite high dilutions (x(IL) > or = 0.2) in DCM.

Interactions and dynamics in electrolyte solutions by dielectric spectroscopy.

Despite its immense abilities to quantify many aspects of ion-ion and ion-solvent interactions, dielectric relaxation spectroscopy (DRS) has long been neglected as a tool for the investigation of the structure and dynamics of electrolyte solutions. The reasons for this are briefly discussed and it is shown that many of the difficulties associated with this technique have been overcome in recent years by technological developments. Representative applications of DRS to the investigation of ion solvation and ion association in electrolyte solutions of chemical, industrial, geochemical and biological interest, including room temperature ionic liquids and polyelectrolyte systems, are discussed. The advantages of linking DRS measurements to information obtained from other experimental techniques and from computer simulations are highlighted.

Systematic Variations of Ion Hydration in Aqueous Alkali Metal Fluoride Solutions.

Aqueous solutions of three alkali metal fluorides-NaF, KF, and CsF-have been studied by dielectric relaxation spectroscopy (DRS) over the frequency range 0.2 ≲ ν/GHz ≤ 89 at 25 °C and at concentrations 0.05 ≲ c/mol L-1 ≲ 1. The combination of these measurements with analogous literature data for RbF(aq) and M'Cl(aq) (M' = Li, Na, K, and Cs) made possible a systematic analysis of the hydration of F- and the alkali metal cations. Unlike the other halide ions, F- was found to have a well-defined hydration shell which contains ∼7 water molecules, consistent with the appearance of a "slow"-water mode at ∼10 GHz in the spectra. Limiting total effective hydration numbers (Zt0) for M'F(aq), obtained from the solvent-related modes, did not follow a simple sequence, varying in the order CsF < NaF < RbF < KF. However, it is shown that this anomalous sequence results from subtle variations in the strength of the M'+-OH2 bonding. Thus, it was established that Zib0(M'+) values, corresponding to the numbers of strongly ("irrotationally") bound (ib) water molecules around the cations, do vary with charge density in the order Li+ ≫ Na+ > K+ > Rb+ > Cs+. It was also found that Zs0(M'+), the number of moderately bound ("slow") water molecules, varied in the same order: K+ > Rb+ > Cs+. However, the presence of ib water molecules in the hydration shells of Li+ and Na+ attenuates their further interaction with surrounding water molecules such that Zs0(M'+) ≈ 0 for both ions.

Cation Hydration and Ion Pairing in Aqueous Solutions of MgCl2 and CaCl2.

Broadband dielectric relaxation spectroscopy (DRS) has been used to investigate aqueous solutions of MgCl2 and CaCl2 up to concentrations of about 1.8 mol L-1 at 25 °C over the frequency range 0.07 ≤ ν/GHz ≤ 89. Detailed analysis of the dominant solvent mode centered at ∼20 GHz showed that both Mg2+ and Ca2+ are strongly solvated, each immobilizing ∼20 water molecules on the DRS timescale. This is consistent with the formation of two well-defined hydration layers around both cations. The hydration shell of Ca2+(aq) was found to be slightly more labile compared with Mg2+(aq). Two or three low-intensity solute-related modes were observed at frequencies ≲10 GHz for MgCl2(aq) and CaCl2, respectively. Two of these modes were attributed to the formation of double-solvent-separated and solvent-shared 1:1 ion pairs. The third mode (observed at very low frequencies and only for some CaCl2 solutions) was thought to be due to an ion-cloud relaxation. No evidence was found for "slow" water or, consistent with the strong cation hydration, for contact ion pairs. The overall association constants for MgCl+(aq) and CaCl+(aq) calculated from the ion-pairing constants were very small but in good agreement with literature values obtained from other techniques.

Enthalpies of Solution of C-Alkylresorcin[4]arenes in Water and Acetonitrile: Hydrophilic and Hydrophobic Effects.

Enthalpies of solution, Δsln H, of six C-alkylresorcin[4]arene ( C-ARA) solids, with alkyl substituents varying systematically from methyl (Me) to hexyl (Hx), have been measured in water, using solubility data, and in acetonitrile, by direct calorimetry. For all of the C-ARAs studied, the values of Δsln H were highly favorable (exothermic) for dissolution into water but were strongly unfavorable (endothermic) for dissolution into acetonitrile (ACN). The differences between the two solvents varied systematically with increasing carbon chain length, from about 100 kJ·mol-1 (for Me) to 140 kJ·mol-1 (for Hx). These extraordinary variances can be attributed to the loss of hydrophilic hydration of the eight -OH groups on the rim of the C-ARAs and also by the loss of (enthalpically favorable) hydrophobic hydration of the alkyl chains upon transfer from the highly structured, strongly H-bonding water to the aprotic, relatively weak donor/acceptor ACN. Although Δsln H values for the present C-ARAs in H2O are strongly favorable, they are more than counteracted by even larger negative changes in the entropy of dissolution, Δsln S. This enthalpy/entropy compensation effect is consistent with the low aqueous solubilities (<10-3 mol·kg-1) of the C-ARAs and their slight increase with increasing carbon chain length, which is opposite to typical behavior of the homologous series of organic molecules.

Nature of Monomeric Molybdenum(VI) Cations in Acid Solutions Using Theoretical Calculations and Raman Spectroscopy.

The composition and structures of the two protonated species formed from uncharged molybdic acid, MoO2(OH)2(OH2)20, in strongly acidic solutions have been investigated using a combination of density functional theory calculations, first-principles molecular dynamics simulations, and Raman spectroscopy. The calculations show that both protonated species maintain the original octahedral structure of molybdic acid. Computed p Ka values indicated that the ═O moieties are the proton acceptor sites and, therefore, that MoO(OH)3(OH2)2+ and Mo(OH)4(OH2)22+ are the probable protonated forms of Mo(VI) in strong acid solutions, rather than the previously accepted MoO2(OH)2- x(OH2)2+ x x+ ( x = 1, 2) species. This finding is shown to be broadly consistent with the observed Raman spectra. Structural details of MoO(OH)3(OH2)2+ and Mo(OH)4(OH2)22+ are reported.

Molar volumes and heat capacities of electrolytes and ions in N,N-dimethylformamide.

Densities and heat capacities of various 1:1 and higher-charged electrolytes have been measured in N,N-dimethylformamide (DMF) at 25 degrees C using a series-connected flow densimeter and Picker calorimeter. Standard molar volumes V (o) and isobaric heat capacities C p (o) derived from these data were split into their ionic contributions using the tetraphenylphosphonium tetraphenylborate (TPTB) reference electrolyte assumption. The values so obtained have enabled a meaningful separation of the effects of cationic size and charge for the first time in a nonaqueous solvent. As in water, V (o)(M (n+) ) values in DMF are markedly more negative for higher-charged cations due to increasing electrostriction of the solvent. In contrast, ionic charge has a much smaller effect on C p (o)(M (n+) ) in DMF than in water. Ionic volumes in DMF show the expected dependence on size but those of small monatomic monovalent cations and anions imply a significant difference in accessibility of the electron donor and acceptor sites on the DMF molecule. Ionic heat capacities in DMF show a relatively weak dependence on ionic size that, when corrected for charge, is opposite to that in water. Both V (o)(R 4N (+)) and C p (o)(R 4N (+)) in DMF show the usual linear dependence on carbon number but differ from their values in aqueous solution due to the absence of hydrophobic interactions in DMF.

From ionic liquid to electrolyte solution: dynamics of 1-N-butyl-3-N-methylimidazolium tetrafluoroborate/dichloromethane mixtures.

Dielectric spectra have been measured at 25 degrees C for mixtures of the room temperature ionic liquid 1- N-butyl-3- N-methylimidazolium tetrafluoroborate (IL) with dichloromethane (DCM) over the entire composition range at frequencies 0.2 less than or approximately nu/GHz < or = 89. The spectra could be satisfactorily fitted by assuming only two relaxation modes: a Cole-Cole process at lower frequencies and a Debye process at higher frequencies. However, detailed analysis indicated that both spectral features contain additional modes, which could not be resolved due to overlaps. The spectra indicate that the IL appears to retain its chemical character to extraordinarily high levels of dilution ( x IL greater than or approximately 0.5) in DCM. At even higher dilutions ( x IL less than or approximately 0.3), the IL behaves as a conventional but strongly associated electrolyte.

Interactions and dynamics in ionic liquids.

Precise dielectric spectra have been determined at 25 degrees C over the exceptionally broad frequency range of 0.1

Scandium sulfate complexation in aqueous solution by dielectric relaxation spectroscopy.

Ion association in aqueous solutions of scandium sulfate has been investigated at 25 degrees C and at concentrations from 0.01 to 0.8 M by broadband dielectric spectroscopy over the frequency range 0.2

Dielectric spectroscopy of hydrogen bond dynamics and microheterogenity of water + dioxane mixtures.

Mixtures of water or D2O + 1,4-dioxane (DX) have been studied at 25 degrees C by dielectric relaxation spectroscopy over a wide range of frequencies (0.2 < or = nu/GHz < or = 89) for DX mole fractions 0 < or = x2 < or = 0.67. The spectra were best fitted by the sum of two Debye terms. The slower process was assigned to the cooperative relaxation of the hydrogen-bond network of water, whereas the faster mode reflects the dynamics of H2O molecules in a DX-rich environment. Analysis of the relaxation parameters revealed a largely microheterogeneous structure of the mixtures. The marked slowing-down of the cooperative mode on addition of DX is ascribed to the reduction of available H-bond acceptor sites and geometrical constraints on the H2O molecules in the water-rich regions.