Dihydrogen Citrate Research Articles

The anion of choline-based ionic liquids tailored interactions between ionic liquids and bovine serum albumin, MCF-7 cells, and bacteria

Choline-based ionic liquids (ILs) have been widely applied because of their good biocompatibility. Herein, the toxicity of choline-based ILs containing different anions was studied by UV–vis absorption spectra, fluorescence spectra, MTT assays and antibacterial experiments. The results explained that choline chloride ([Ch][Cl]) had no obvious effect on the conformation of bovine serum albumin (BSA), while the conformation could be slightly changed by choline bromide ([Ch][Br]). In the presence of choline iodide ([Ch][I]), choline bitartrate ([Ch][Bit]) and choline dihydrogen citrate ([Ch][Dhc]), the conformation of BSA changed significantly. The quenching mechanisms of [Ch][Bit] and [Ch][Dhc] were static quenching procedure, while there were charge transfer quenching and static quenching for [Ch][I]. ILs combined with BSA in spontaneous manner driven by hydrogen bond and van der Waals force, which was proved by thermodynamic constants and molecular docking. The toxicity of the five ILs to mammalian cells and bacteria came to a similar conclusion. [Ch][Cl] had little toxicity to cells, which was less than [Ch][Br] and [Ch][I]. [Ch][Bit] and [Ch][Dhc] were more toxic. These results provide more information to understand the effect of anions on choline-based ILs, in order to find low toxic choline-based ILs that can be used in biological and pharmaceutical fields.

Sustainable liquid supports for laccase immobilization and reuse: Degradation of dyes in aqueous biphasic systems.

Novel liquid supports for enzyme immobilization and reuse based on aqueous biphasic systems (ABS) constituted by cholinium-based ionic liquids (ILs) and polymers for the degradation of dyes are here proposed. The biocatalytic reaction for dye decolorization using laccase occured in the biphasic medium, with the enzyme being "supported" in the IL-rich phase and the dye and degradation products being enriched in the polymer-rich phase. An initial screening of the laccase activity in aqueous solutions of ABS constituents, namely cholinium dihydrogen citrate ([Ch][DHC]), cholinium dihydrogen phosphate ([Ch][DHP]), cholinium acetate ([Ch][Acet]), polypropylene glycol 400 (PPG 400), polyethylene glycol 400 (PEG 400) and K2 HPO4 was carried out. Compared to the buffered control, a relative laccase activity of up to 170%, 257%, and 530% was observed with PEG 400, [Ch][DHP], and [Ch][DHC], respectively. These ABS constituents were then investigated for the in situ enzymatic biodegradation of the Remazol Brilliant Blue R (RBBR) dye. At the optimized conditions, the ABS constituted by PPG 400 at 46 wt% and [Ch][DHC] at 16 wt% leads to the complete degradation of the RBBR dye, further maintaining the enzyme activity. This ABS also allows an easy immobilization, recovery, and reuse of the biocatalyst for six consecutive reaction cycles, achieving a degradation yield of the dye of 96% in the last cycle. In summary, if properly designed, high enzymatic activities and reaction yields are obtained with ABS as liquid supports, while simultaneously overcoming the safety and environmental concerns of conventional organic solvents used in liquid-liquid heterogeneous reactions, thus representing more sustainable biocatalytic processes.

Crystal growth and properties measurements of nickel doped potassium dihydrogen citrate crystals

Potassium dihydrogen citrate (KDC) is well-recognized food additive and mineral found in various fruits which make it interesting to study its properties under the influence of toxic metal doping. Pure and different mol% Ni2+-doped KDC crystals were grown using slow-solvent evaporation technique at room temperature. The grown crystals exhibits needle-shaped morphology. EDAX analysis reveals apparent concentration of Ni2+ in different mol% Ni2+-doped KDC. Indexing of powder XRD patterns of pure and different mol% Ni2+-doped KDC reveals triclinic symmetry of grown crystals. W–H analysis reveals presence of lattice strain under the incorporation of Ni2+ doping in the host lattice of KDC. Bond assignments corresponding to various functional groups present in grown crystals is studied using the FT-IR spectroscopic study. The modification in thermal stability of KDC due to Ni2+ doping is studied using TGA analysis. The SEM study has shown grain growth in KDC crystal due to Ni2+ doping. The presence of grain, grain boundary effect and relaxation mechanism involved in transport properties of pure and different mol% Ni2+ doped KDC is reported using the Impedance–Modulus spectroscopic studies. Dielectric studies reveal modification in dielectric constant, dielectric loss and a.c. conductivity of KDC due to Ni2+ doping. The structural defect mechanism is well studied using the photoluminescence.

Crystal structure of tofacitinib dihydrogen citrate (Xeljanz®), (C16H21N6O)(H2C6H5O7)

The crystal structure of tofacitinib dihydrogen citrate (tofacitinib citrate) has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Tofacitinib dihydrogen citrate crystallizes in space group P212121 (#19) with a = 5.91113(1), b = 12.93131(3), c = 30.43499(7) Å, V = 2326.411(6) Å3, and Z = 4. The crystal structure consists of corrugated layers perpendicular to the c-axis. Within the layers, cation⋯anion and anion⋯anion hydrogen bonds link the fragments into a two-dimensional network parallel to the ab-plane. Between the layers, there are only van der Waals contacts. A terminal carboxylic acid group in the citrate anion forms a strong charge-assisted hydrogen bond to the ionized central carboxylate group. The other carboxylic acid acts as a donor to the carbonyl group of the cation. The citrate hydroxy group forms an intramolecular charge-assisted hydrogen bond to the ionized central carboxylate. Two protonated nitrogen atoms in the cation act as donors to the ionized central carboxylate of the anion. These hydrogen bonds form a ring with the graph set symbol R2,2(8). The powder pattern has been submitted to ICDD® for inclusion in the Powder Diffraction File™ (PDF®).

Validation of a Model Formula for Predicting the Long-Term Corrosion Rate of Carbon Steel Pipes in Freshwater

In Japan, conduits buried underground protect telecommunication cables, and it is desirable to continue to use these conduits as much as possible. Hence, it is important to grasp the deterioration in considering the use limit. There are several kinds of conduits, and carbon steel conduits are mainly utilized especially. Though the carbon steel conduits outer surface contacting with the soil is coated with asphalt jute or polyethylene, the inner surface is protected only with synthetic resin paint. Since the conduit inner surface is connected to the manhole, it may be filled with stagnant water such as groundwater or rainwater. Therefore, it is necessary to predict the long-term corrosion rate of carbon steel conduits in fresh water.We carried out a test to measure the average corrosion depth converted from the weight loss by immersing test pieces made from a carbon steel conduit in distilled water at 60 °C and in a manhole stagnant water as a sample. The test pieces were obtained by cutting the steel pipe into 50 mm, removing the coating film on the inner and outer surfaces, shaping it to a thickness of 3 mm, and applying a urethane coating film on the outer surface so that bare steel was exposed only on the inner surface. This test continued for about 1500 days, and test pieces were brought out every 45 days for the specimens immersed in distilled water and every 90 days for the specimens immersed in manhole. The corrosion products were removed using 10% ammonium dihydrogen citrate heated to 80 °C, and weight loss of each test piece was measured. Using this result, the applicability of the model equation proposed by Ozawa et al. in 2017 was considered. Ozawa et al. developed a model to predict the corrosion depth of carbon steel pipes in neutral static water based on temperature, salinity, and Larson Skold Index (LSI). The model assumes that the corrosion depth with time is determined by the initial corrosion rate, time and film resistance coefficient. Salinity and temperature determine the initial corrosion rate, and LSI and temperature determine the film resistance coefficient. In order to apply this model, the pH, chloride ion and sulfate ion of manhole stagnant water were measured by ion chromatography. The pH was 7.8, Cl- was 2.9 mg/l, and SO42- was 5.3 mg/l. The value of hydrogen carbonate ion has not been measured yet, and 207.5 mg/l, which is the average value measured in 1960 in Tokyo 45 manholes, is used. At this time, the film resistance coefficient becomes 2909.3. The temperature and salinity of the manhole reservoir water were 20 ° C and 0.05 ‰, respectively. The model was applied to distilled water with salinity of 0.01 ‰ and LSI with 1.The results of observed corrosion depth is shown on the vertical axis, and the results are shown in the log diagram with the predicted values obtained from the model equation of Ozawa et al. on the horizontal axis. The corrosion depth on day 45 after immersion in distilled water and the corrosion amount on day 90 after immersion in manhole reservoir water agree with the measured value predicted from the model equation, but the observed corrosion depth tends to be larger than the value derived from the model equation after that. The original model equation showed good agreement when compared with the test results at approximately 500 hours. It may be considered that this model equation is applicable in 45 days (1080 hours), but it is highly possible that the corrosion depth becomes larger than the model equation in the long term. In addition, the corrosion rate of the specimen immersed in the manhole deviates more from the model equation. Figure shows a photograph in which corrosion products were observed with an electron microscope on the test specimen as of 1321 days, and it can be seen that cracks of several μm in width were generated just above the base metal and at 150 μm to 300 μm positions, respectively. There is a possibility that the corrosion rate becomes faster than expected due to the influence of the cracks. In addition, though the stagnant water is presumed as still water in the usual time, the flow with the inflow of the water may be generated depending on the season. Considering these factors, it is possible to improve the long-term prediction accuracy of carbon steel conduits. Figure 1

Supercritical carbon dioxide and eutectic solvent in conjunction: Novel method for in-situ solvent preparation-dissolution and uranium extraction from solid matrices

Halide anion free hydrophilic Deep Eutectic Solvent (DES) based on choline dihydrogen citrate and urea (1:2 mol ratio) was prepared and successfully employed for dissolution of uranium compounds. Dissolution study was carried out with oxides viz. UO2, UO3 and crude yellow cakes viz. magnesium diuranate, sodium diuranate. Novel route of in-situ, single step eutectic solvent preparation and U compound dissolution was found to be promising in terms of better dissolution efficiency and process simplification. The resultant systems were probed with electrochemistry and UV–Vis spectrophotometry to get an insight about the uranium species. In all the four systems prepared by in-situ mode, stabilization of uranium in U(VI) oxidation state in the form of oxo species was indicated. This halide anion free eutectic system was amenable to be used in SC CO2 extraction set-up. SC CO2 extraction of uranium dissolved in eutectic solvent was found to be influenced by various extraction conditions viz. pressure, temperature, static and dynamic time. Uranium extraction efficiency of upto 65% for oxide system was achievable by SC CO2 modified with TTA.

Liquid-liquid equilibrium of aqueous two-phase systems formed by non-ionic surfactant (Triton X-165 or Triton X-305) and ionic liquid based on the choline cation (choline bitartrate or choline dihydrogen citrate)

Liquid-liquid equilibrium data for aqueous two-phase systems (ATPSs) formed by Triton X-165 or Triton X-305 + ionic liquid based on the choline cation (choline bitartrate or choline dihydrogen citrate) + water were obtained at different temperatures (298.2, 313.2, and 328.2 K). The effects of temperature, electrolyte anion, and surfactant on the equilibrium data were evaluated. For all the ATPSs investigated, the upper phase was found to be surfactant-rich and the lower phase was electrolyte-rich. An increase of the biphasic region was observed with increasing temperature, showing that the phase separation process was endothermic and entropically driven. The potential of phase segregation between the different anions studied was in the order bitartrate > dihydrogen citrate, which was attributed to the different capacities of the anions to form hydration complexes and induce a surfactant salting-out effect. The TX-305 surfactant was more efficient in inducing phase segregation, compared to the TX-165 surfactant, indicating that the molar mass/hydrophobicity balance of the surfactant determined the immiscibility region of the ATPS.

Unravelling the interactions between biomedical thermoresponsive polymer and biocompatible ionic liquids

Studies on the phase behavior of thermoresponsive polymers (TRPs) in the presence of ionic liquids (ILs) are an emerging area for the preparation and design of new polymeric materials. The search to understand the influence of ILs on polymers has come into the limelight as a great challenge. Hitherto, limited work on the phase transition behavior of TRPs in the presence of ILs is available. In this work, we studied the phase behavior of poly-N-isopropylacrylamide (PNIPAM) in presence of cholinium chloride ([Ch]Cl), cholinium acetate ([Ch][Ac]), cholinium bitartrate ([Ch][Bit]) and cholinium dihydrogen citrate ([Ch][DHCit]) using various techniques such as UV–Visible absorption spectroscopy, steady-state fluorescence spectroscopy, thermal fluorescence spectroscopy, viscosity (ƞ) and dynamic light scattering (DLS). All cholinium-based ILs studied show qualitatively and quantitatively a similar phase behavior, suggesting it to be quite resilient with respect to changes in the anion of the ILs. However, concentration and orientation of ILs have a varied effect on the phase transition temperature and on the aggregation behavior of PNIPAM. Our temperature dependent experimental results explicitly signifies that lower critical solution temperature (LCST) values decrease with increasing the temperature and concentration of studied ILs, which indicates that hydrophobic interactions are dominating. Anions of IL with their charge densities, hydration capacities and hydration energies leads to the hydrophobicity of PNIPAM + IL aqueous solution. High polarity, owing to the charge of the carboxylate groups in [Ch][DHCit] and [Ch][Bit], and hydrogen bond acceptor capability of the Cl− anion causes their affinity for water inducing ability. This is the first report on the influence of cholinium-based ILs on the phase behavior of the PNIPAM. The current research work provides significant information on the phase transition and aggregation behavior of TRPs in ILs, which paves the way for potential applications in various fields.

Effect of Cr3+ on growth, thermal, photoluminescence and electrical properties of potassium dihydrogen citrate single crystal

Potassium Dihydrogen Citrate (KDC) is well recognized food additive and hence it is interesting to investigate the influence of toxic metal doping on its properties. The pure and 0.2 mol% Cr3+ doped KDC crystals are grown using solvent evaporation technique at room temperature. The grown crystals exhibits needle shape morphology. The EDAX analysis confirms the presence of chromium along with the constituent elements of KDC crystal. The powder XRD indicates the triclinic symmetry of the grown crystals. The FT-IR spectroscopic study indicates the presence of various functional groups in the pure and doped crystals. The Cr3+ improves the thermal stability of KDC crystal. The influence of Cr3+ doping is clearly shown by large value of dielectric constant of doped KDC crystals compared to pure KDC. The variation of dielectric constant, dielectric loss and A.C. conductivity with frequency are studied. The Photoluminescence study confirms the defect in hydrogen bonding network of KDC crystal due to doping of Cr3+.

H-Bonded anion-anion complexes in fentanyl citrate polymorphs and solvates.

Herein we report the experimental observation (X-ray characterization) of two different binding modes in H-bonded anion-anion complexes (anion = citrate) in N-(1-(2-phenylethyl)-4-piperidinylium)-N-phenyl-propanamide-citrate (fentanyl citrate). High level DFT calculations indicate that both types of anion-anion complexes (one with two and the other with four H-bonds) are thermodynamically unstable but kinetically stable with respect to the isolated anions with activation barriers as high as 14 kcal mol-1.

Efficacy of Silver Dihydrogen Citrate and Steam Vapor against a Human Norovirus Surrogate, Feline Calicivirus, in Suspension, on Glass, and on Carpet.

Carpets and other soft surfaces have been associated with prolonged and reoccurring human norovirus (HuNoV) outbreaks. Environmental hygiene programs are important to prevent and control HuNoV outbreaks. Despite our knowledge of HuNoV transmission via soft surfaces, no commercially available disinfectants have been evaluated on carpets. Our aim was to adapt a current standardized method for virucidal testing by assessing two disinfection technologies, silver dihydrogen citrate (SDC) and steam vapor, against one HuNoV surrogate, feline calicivirus (FCV), on wool and nylon carpets. First, we evaluated the effect of both technologies on the appearance of carpet. Next, we evaluated the efficacy of SDC in suspension and the efficacy of SDC and steam vapor against FCV on a glass surface, each with and without serum. Lastly, we tested both technologies on two types of carpet, wool and nylon. Both carpets exhibited no obvious color changes; however, SDC treatments left a residue while steam vapor left minor abrasions to fibers. SDC in suspension and on glass reduced FCV by 4.65 log10 and >4.66 log10 PFU, respectively, but demonstrated reduced efficacy in the presence of serum. However, SDC was only efficacious against FCV on nylon (3.62-log10 PFU reduction) and not wool (1.82-log10 PFU reduction). Steam vapor reduced FCV by >4.93 log10 PFU on glass in 10 s and >3.68 log10 PFU on wool and nylon carpet carriers in 90 s. There was a limited reduction of FCV RNA under both treatments compared to that of infectivity assays, but RNA reductions were higher in samples that contained serum.IMPORTANCE Human noroviruses (HuNoV) account for ca. 20% of all diarrheal cases worldwide. Disease symptoms may include diarrhea and vomit, with both known to contribute to transmission. The prevention and control of HuNoV are difficult because they are environmentally resilient and resistant to many disinfectants. Several field studies have linked both hard and soft surfaces to HuNoV outbreaks. However, many disinfectants efficacious against HuNoV surrogates are recommended for hard surfaces, but no commercially available products have demonstrated efficacy against these surrogates on soft surfaces. Our research objectives were to evaluate liquid and steam-based technologies in suspension and on hard surface carriers in addition to adapting and testing a protocol for assessing the virucidal effects of disinfection technologies on carpet carriers. These results will inform both the government and industry regarding a standard method for evaluating the virucidal effects of disinfectants on carpet while demonstrating their efficacy relative to suspension and hard-surface tests.

Salting out potential of cholinium dihydrogen citrate in aqueous solution of Triton surfactants

Abstract Aqueous solutions of the non-ionic surfactants Triton X-100 and Triton X-102 have been salted out with the biocompatible ionic liquid cholinium dihydrogencitrate (N 1112OH DHC). The phase boundary for {Triton X-100 or Triton X-102 + N 1112OH DHC + H 2 O} was ascertained at T = (293.15, 303.15, 313.15 and 323.15) K and 0.1 MPa. The binodal data were modelled by one polynomial and three exponential equations, and the tie-line data were suitably correlated by means of Othmer-Tobias, Bancroft and Setschenow empirical models. The experimental results allowed concluding that the increase of temperature and the hydrophobicity of the surfactant led to the shift of the binodal curve to the water vertex.

Proton-Coupled Electron Transfer and Substituent Effects in Catechol-Based Deep Eutectic Solvents: Gross and Fine Tuning of Redox Activity.

The 1,2-diol moiety in a variety of substituted catechols allows formation of room temperature ionic melts in a 2:1 ratio with choline chloride or choline dihydrogen citrate. These deep eutectic solvents were 4.3-6.6 M in redox active catechols. Substituents on 3- and 4-substituted catechols shift both E° and pKa such that Hammett parameters predict the observed Ep for oxidation in square wave voltammetry. The proton acceptor for the proton-coupled oxidation shifts the observed Ep more strongly than the substituents within the substituents and acceptors reported here. The shift is predicted well by the pKa of the conjugate acid of the proton acceptor, i.e., water in aqueous solutions or chloride or dihydrogen citrate in the DESs in this study. Together, the substituent and the proton acceptor allow gross and fine-tuning of the oxidation potential for catechol over 750 mV, the first demonstration of control of the thermodynamics of proton-coupled electron transfer in deep eutectic solvents. Changing the substituents on the HBD affords fine control in tens of millivolts, while changing the base strength of the anion of the organic salt affords gross control across hundreds of millivolts.

Prawn Shell Derived Chitin Nanofiber Membranes as Advanced Sustainable Separators for Li/Na-Ion Batteries.

Separators, necessary components to isolate cathodes and anodes in Li/Na-ion batteries, are consumed in large amounts per year; thus, their sustainability is a concerning issue for renewable energy storage systems. However, the eco-efficient and environmentally friendly fabrication of separators with a high mechanical strength, excellent thermal stability, and good electrolyte wettability is still challenging. Herein, we reported the fabrication of a new type of separators for Li/Na-ion batteries through the self-assembly of eco-friendly chitin nanofibers derived from prawn shells. We demonstrated that the pore size in the chitin nanofiber membrane (CNM) separator can be tuned by adjusting the amount of pore generation agent (sodium dihydrogen citrate) in the self-assembly process of chitin nanofibers. By optimizing the pore size in CNM separators, the electrochemical performance of the LiFePO4/Li half-cell with a CNM separator is comparable to that with a commercialized polypropylene (PP) separator. More attractively, the CNM separator showed a much better performance in the LiFePO4/Li cell at 120 °C and Na3V2(PO4)3/Na cell than the PP separator. The proposed fabrication of separators by using natural raw materials will play a significant contribution to the sustainable development of renewable energy storage systems.

Interaction studies of cholinium-based ionic liquids with calf thymus DNA: Spectrophotometric and computational methods

Ionic liquids (ILs) are emerging class of low-melting solid which have potential to replace conventional solvents. DNA is one of the primary targets of many synthetic agents which are classified as carcinogens; most of them bind to the DNA irreversibly causing mutation of the genome. Thus, it is essential to study the nature and mode of binding of new molecules to predict its toxicity. In the present study, we carried out photo-physical and computational studies on interaction of aqueous cholinium-based ILs (cholinium chloride, cholinium dihydrogen citrate, cholinium bicarbonate, cholinium bromide) with calf thymus DNA (ct-DNA). The experimental (absorption and fluorescence) and docking studies indicated weak interaction between the cholinium-based ILs and double stranded ct-DNA, mainly through minor grooves. Since the strength of binding was quite weak, a safe nature of cholinium-based ILs could be expected. However, COSMO-RS studied carried out using individual DNA bases (A, T, G & C) and cholinium-based ILs showed propensity of the latter class of chemicals with the biomolecules.

Probing intermolecular interactions in a diethylcarbamazine citrate salt by fast MAS 1H solid-state NMR spectroscopy and GIPAW calculations

Fast magic-angle spinning (MAS) NMR is used to probe intermolecular interactions in a diethylcarbamazine salt, that is widely used as a treatment against adult worms of Wuchereria bancrofti which cause a common disease in tropical countries named filariasis. Specifically, a dihydrogen citrate salt that has improved thermal stability and solubility as compared to the free form is studied. One-dimensional 1H, 13C and 15N and two-dimensional 1H–13C and 14N–1H heteronuclear correlation NMR experiments under moderate and fast MAS together with GIPAW (CASTEP) calculations enable the assignment of the 1H, 13C and 14N/15N resonances. A two-dimensional 1H–1H double-quantum (DQ) –single-quantum (SQ) MAS spectrum recorded with BaBa recoupling at 60kHz MAS identifies specific proton-proton proximities associated with citrate-citrate and citrate-diethylcarbamazine intermolecular interactions.

Crystal structure of caesium di-hydrogen citrate from laboratory X-ray powder diffraction data and DFT comparison.

The crystal structure of caesium di-hydrogen citrate, Cs+·H2C6H5O7-, has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The coordination polyhedra of the nine-coordinate Cs+ cations share edges to form chains along the a-axis. These chains are linked by corners along the c-axis. The un-ionized carb-oxy-lic acid groups form two different types of hydrogen bonds; one forms a helical chain along the c-axis, and the other is discrete. The hy-droxy group participates in both intra- and inter-molecular hydrogen bonds.

Efficacy of a disinfectant containing silver dihydrogen citrate against GI.6 and GII.4 human norovirus.

Human norovirus is a major public health burden and is resistant to numerous sanitizers and disinfectants. In this study, we tested the efficacy of an antimicrobial product containing a blend of silver ions and citric acid (silver dihydrogen citrate; SDC) against GI.6 and GII.4 HuNoV. Pure® hard surface disinfectant (Pure Bioscience, El Cajon, CA) was evaluated using ASTM International virucidal suspension and stainless steel carrier assays. The effect of SDC (or citrate alone) exposure on viral integrity was evaluated using RT-qPCR, transmission electron microscopy, sodium dodecyl sulphate-polyacrylamide gel electrophoresis/Western blot analysis and a receptor-binding assay. Suspension assays showed a 4·0 log10 reduction in RNA copy number within 5min, while carrier assays showed a 2·0-3·0 log10 reduction in 30min. Incorporating a simulated soil load into the sample matrix significantly reduced product efficacy. Treated particles displayed deformation and aggregation, a 50% reduction in viral capsid protein band intensity, and an 80% reduction in histo-blood group antigen receptor-binding ability. Our results suggest that SDC acts exclusively on the viral capsid, and shows efficacy against HuNoV when used on precleaned surfaces. This study sheds light on the mechanisms and efficacy of a novel antimicrobial against HuNoV. Our results suggest: (i) silver ions exclusively target the viral capsid, and not the RNA genome; (ii) citrate is not crucial for HuNoV capsid deformation.

A second polymorph of sodium di-hydrogen citrate, NaH2C6H5O7: structure solution from powder diffraction data and DFT comparison.

The crystal structure of a second polymorph of sodium di-hydrogen citrate, Na(+)·H2C6H5O7 (-), has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The powder pattern of the commercial sample used in this study did not match that corresponding to the known crystal structure [Glusker et al. (1965). Acta Cryst. 19, 561-572; refcode NAHCIT]. In this polymorph, the [NaO7] coordination polyhedra form edge-sharing chains propagating along the a axis, while in NAHCIT the octa-hedral [NaO6] groups form edge-sharing pairs bridged by two hy-droxy groups. The most notable difference is that in this polymorph one of the terminal carboxyl groups is deprotonated, while in NAHCIT the central carboxyl-ate group is deprotonated, as is more typical.

Conversion of glucose into 5-hydroxymethylfurfural with boric acid in molten mixtures of choline salts and carboxylic acids

The conversion of glucose into a potential platform chemical for fuels and plastics, 5-hydroxymethylfurfural (HMF), has been studied using B(OH)3 as a promoter in different solvents, namely molten mixtures made of choline salts and carboxylic acids, with the aim of developing an inexpensive and less harmful alternative to Cr/ionic liquid systems. Choline chloride-based molten mixtures afforded poor yields of HMF, whereas the yields were improved by replacing choline chloride with choline dihydrogen citrate. The combination of choline dihydrogen citrate and glycolic acid was the best choice, providing an HMF yield of ∼60% at 140 °C within 4 h by adding a small volume of water as a co-solvent.