Acetic Acid Anion Research Articles

Dinuclear Nitrato Coordination Compounds with Bis(3,5‐tert‐butylpyrazol‐1‐yl)­acetate

AbstractTwo dinuclear centrosymmetric coordination compounds with the bis(3,5‐di‐tert‐butylpyrazol‐1‐yl)acetic acid anion (L– = bdtbpza), namely, violet [Co(bdtbpza)(NO3)]2 (1) and turquoise [Cu(bdtbpza)(NO3)]2 (2), are reported. Around each metal(II) ion, the L– ligand is κ3‐N,N,O coordinated, and the M–O bonds are significantly longer than both M–N bonds. The coordination sphere is completed by short nitrato and M–O bonds to a ligand that is already κ3‐N,N,O coordinated to the adjacent intra‐dinuclear metal center. Therefore, each L– ligand has a total coordination number of four but with different carboxylate modes, namely, κ4‐N,N,O,O (1,1) in 1 and κ4‐N,N,O,O′ (1,3) in 2 for the C(1)–O–C(2) group. Thus, the coordination spheres are MO2N2O in both cases, though 1 is distorted trigonal bipyramidal, whereas 2 is square pyramidal. Antiferromagnetic (AFM) coupling (17 cm–1) is seen only in 1, though the best fit was obtained with consideration of spin–orbit coupling along with zero‐field splitting owing to exchange anisotropy. The new dinuclear nitrato species might be alternatives to previously reported mimics of enzyme active sites.

Sensitivity improvement in hydrophilic interaction chromatography negative mode electrospray ionization mass spectrometry using 2-(2-methoxyethoxy)ethanol as a post-column modifier for non-targeted metabolomics

The application of ammonia acetate buffered liquid chromatography (LC) eluents is known to concomitantly lead to ion suppression when electrospray ionization mass spectrometry (ESI–MS) detection is used. In negative ESI mode, post column infusion of 2-(2-methoxyethoxy)ethanol (2-MEE) was shown in the literature to help to compensate this adverse effect occurring in reversed phase liquid chromatography mass spectrometry (RP-LC–MS) analyses. Here a setup of direct infusion and hydrophilic interaction chromatography (HILIC) post-column infusion experiments was established in order to investigate systematically the beneficial effects of 2-MEE. We demonstrate that, 2-MEE can help to improve ESI–MS sensitivity in HILIC too and reveal analyte structure specific behaviors. Our study indicates that 2-MEE especially improves ESI response for small and polar molecules. The ESI response of stable isotope labeled amino acids spiked into biological matrices increases up to 50-fold (i.e. D5-l-glutamic acid) when post column infusion of 2-MEE is applied. A non-targeted analysis of a pooled urine sample via HILIC–ESI–QTOF–MS supports this hypothesis. In direct infusion, the combined application of an ammonia acetate buffered solution together with 2-MEE results in an improved ESI response compared to a non-buffered solution. We observed up to 60-fold increased ESI response of l-lysine. We propose this effect is putatively caused by the formation of smaller ESI droplets and stripping of positive charge from ESI droplets due to evaporation of acetic acid anions. In summary, post-column infusion of 2-MEE especially enhances ESI response of small and polar molecules. Therefore it can be regarded as a valuable add-on in targeted or non-targeted metabolomic HILIC–MS studies since this method sets a focus on this molecule category.

Effect of attendant anions on zinc adsorption and transformation in chernozem

The effect of anions on the adsorption and mechanism of interaction of zinc cations with a solid soil phase was established. Acetic acid anions had the greatest influence on bond strength between metal and soil particle surfaces, while the effect of nitric acid anions was the lowest. The difference in amount of mobile forms of zinc extracted by the soil depends on the dose and form of the zinc. The influence of the attendant anions on the content of mobile metal forms in the soil decreases in the order: PO42−≈Cl−>NO3−>SO42−>СН3СОО−>О−.

Effect of Anions on Morphology Control of Brushite Particles

Brushite (DCPD, CaHPO4·2H2O) crystals are of great significance in a range of fields including biology, medicine, chemistry, and materials science. One important issue is the control of their morphology; when the crystal growth conditions are changed, the morphology and surface crystal conditions also change. The chemical reaction behavior depends strongly on the surface condition of the particles. Here, we report the effect of coexisting anions on the morphology control of DCPD particles. We synthesized the particles through a liquid-phase reaction by mixing a starting solution of ammonium dihydrogen phosphate (NH4H2PO4) and calcium salts. Calcium nitrate (Ca (NO3)2) and calcium acetate (Ca (CH3COO)2) were used as the calcium sources to clarify the pH dependence of the morphology. We mixed the solutions with the same pH values and agitated them, and observed the products by scanning electron microscopy (SEM) and X-ray diffraction (XRD); the DCPD morphology varies from petal-like to parallelogram structures depending on the initial pH value of the solution and the combination of the starting mixture. The effect of the acetic acid anion is to increase the driving force for the generation of DCPD crystal nuclei.

Synthesis, Crystal Structure, Luminescence and Thermal Stability of a New Coordination Polymer Constructed by Europium(III) and 2,4‐Dichlorophenoxyacetate

AbstractA new coordination polymer {[Eu2(Cl2C6H3OCH2COO)6(H2O)4]·(DMF)4·(H2O)2}n with 2,4‐dichlorophenoxy acetic acid as the ligand has been synthesized. The crystal data for this complex are as follows: monoclinic, space group P2(1)/n, a=0.86474(17) nm, b=3.2475(7) nm, c=1.3843(3) nm, β=92.81(3) °, V=3.8827(13) nm3, Dc=1.718 g/cm3, Z=2, µ(Mo Kα)=2.093 mm−1, F(000) =2008, final discrepancy factors R1=0.0454, wR2=0.1165. The crystal structure shows that the title complex forms one‐dimensional chain structure by bridging 2,4‐dichlorophenoxy acetic acid anions. Every centric europium(III) ion is coordinated with ten oxygen atoms from five 2,4‐dichlorophenoxy acetic acid anions and two water molecules, giving a ten‐coordinated distorted bicapped square antiprism geometry. The luminescent property and thermal stability of the complex are also studied.

ChemInform Abstract: Solid Supported Reagents and Reactions. Part 20. Synthesis of Herbicides Using Polymer Supported 2,4‐Dichlorophenoxy Acetic Acid Anion.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of Herbicides Using Polymer Supported 2, 4-Dichlorophenoxy Acetic Acid Anion1

2, 4-Dichlorophenoxy acetic acid anion supported on anion exchange resin (Tulsion A-27 Chloride form) was treated with appropriate dihalide in acetonitrile at 25°C or 80 – 85°C to give corresponding diesters of 2, 4-dichlorophenoxy acetic acid as effective herbicides. This paper has been dedicated to Prof. M. S. Wadia (University of Pune) on occasion of his 60th birthday. This paper is in the series of solid supported reagents and reactions part 20. For part 19, see Gajare, A. S.; Shingare, M. S. and Bandgar, B. P. Communicated.

The Crystal Structure of an “Old” Potassium Uranyl Acetate, K(UO2)(CH3COO)3 · 0.5 H2O

AbstractThe uranyl group in the title compound, K(UO2)(CH3COO)3 · 0.5 H2O is sixfold coordinated by three bidentate acetic acid anions. It crystallizes tetragonal, space group I41/a (N° 88 Int. Tab.) with Z = 16 and a = 1447.1(4), c = 2626.5(8) pm.The crystal structure was solved by using 2056 unique reflections Fo ° 4σ (Fo) with a final wR2 value of 0.1234 (SHELXL‐93).Individual molecules are linked by hydrogen bonds between coordinated water molecules and acetate O atoms.

Potential Energy Surfaces for Proton Abstractions from Acetic Acid

The abstractions of hydrogen from both carbon and oxygen in acetic acid by hydride, fluoride, and hydroxide anions have been studied using ab initio electronic structure calculations. Molecular structures were optimized at the Hartree-Fock level of theory using the 6-31++G(d,p) basis set. For energetics, the 6-311++G(d,p) basis set was used, with second- and fourth-order perturbation theory corrections, for both minima and transition states. For the hydride and fluoride ion abstractions of hydrogen from carbon, a small activation energy exists at the Hartree-Fock level, but vanishes when correlation energy corrections are introduced. No other barriers are found for the abstraction reactions, but intermediate minima are found on the F{sup -} + CH{sub 3}COOH {yields} FH + {sup -}CH{sub 2}COOH surface and on the analogous OH{sup -} + CH{sub 3}COOH surface. The calculated heats of formation for both acetic acid anions are in good agreement with the experimental value. The fourth-order perturbation theory calculation of the activation energy for the isomerization of acetate to enolate ion is 50.4 kcal/mol. The G2 values for the gas phase acidities of acetic acid at the OH and CH ends of the molecule are 339.3 and 365.8 kcal/mol, respectively. The former result is in good agreementmore » with the experiment. 26 refs., 5 figs., 5 tabs.« less

ESR line shapes and methyl rotation in the acetic acid anion radical

The CH 3COOD − and CD 3COOD − radical anions have been studied by ESR in irradiated crystal acetic acid in the temperature region 77–170 K. The line-shape variations which are due to methyl rotation are simulated with a program based on the Liouville direct method. The activation energy to the motion is evaluated and is found not to be appreciably affected by susbtitution of the methyl protons by deuterons. The activation energies are determined to be 2.2 and 2.5 kcal/mol respectively. Indications of hydrogen bond effects on the activation barrier are also found.

Hydantoin bioisosteres. In vivo active spiro hydroxy acetic acid aldose reductase inhibitors.

The hypothesis that clinical side effects of the aldose reductase inhibitor (ARI) sorbinil were related to its hydantoin ring led to a bioisosteric analysis and replacement of the hydantoin by a spiro hydroxy acetic acid moiety as in 40. These hydroxy acids, compared to hydantoins, showed a similar potency increase on chroman 2-methyl substitution, a similar orthogonal relationship of acidic to aromatic moieties, and similar ARI enantioselectivity. In this series the six-membered spiro hydroxy acetic acid anion array is a bioisostere for a spiro hydantoin anion and leads to ARIs with excellent in vivo activity. In vitro and in vivo activity was improved over 40 by chroman cis 2-methylation as in 4 and by aromatic 6,7-halogen substitution. Compounds with the best acute in vivo activity in rats were compared for chronic in vivo activity. The highest tissue levels and best chronic in vivo activities were found in the racemic 6,7-dichloro and 6-fluoro-7-chloro analogues 18 and 23. ARI activity was enantioselective for 58 and 60, the 2R,4R-enantiomers of 18 and 23. 7-Chloro-6-fluoro-cis-4-hydroxy-2(R)-methyl-chroman-4-acetic acid (60) was selected for phase 1 clinical trials and did not exhibit sorbinil-like hypersensitivity side effects.

Free energy perturbation calculations on models of active sites: Applications to adenosine deaminase inhibitors

AbstractFree energy perturbation calculations were performed to determine the free energy of binding associated with the presence of perhaps an unusual hydroxyl group in the transition state analog of nebularine, an inhibitor of the enzyme adenosine deaminase. The presence of a single hydroxyl group in this inhibitor has been found to contribute −9.8 kcal/mol to the free energy of binding, with a 108‐fold increase in the binding affinity by the enzyme. In this work, we calculate the difference in solvation free energy for the 1,6‐dihydropurine complex versus that of the 6‐hydroxyl‐1,6‐dihydropurine complex to determine if this marked increase in binding affinity is attributed to an unusually hydrophobic hydroxyl group. The calculated ΔG associated for the solvation free energy is −11.8 kcal/mol. This large change in the solvation free energy suggests that this hydroxyl is instead unusually hydrophilic and that the difference in free energy of interaction for the two inhibitors to the enzyme must be at least ca. 20 kcal/mol. Although the crystal structure for adenosine deaminase is currently not known, we attempt to mimic the nature of the active site by constructing models which simulate the enzyme‐inhibitor complex. We present a first attempt at determining the change in free energy of binding for a system in which structural data for the enzyme is incomplete. To do this, we construct what we believe is a minimal model of the binding between adenosine deaminase and an inhibitor. The active site is simulated as a single charged carboxyl group which can form a hydrogen bond with the hydroxyl group of the analog. Two different carboxyl anion models are used. In the first model, the association is modeled between an acetic acid anion and the modified inhibitor. The second model consists of a hydrophobic amino acid pocket with an interior Glu residue in the active site. From these models we calculate the change in free energy of association and the overall change in free energy of binding. We calculate the free energies of interaction both in the absence and presence of water. We conclude from this that the presence of a single suitably placed‐CO−2 group probably cannot explain the binding effect of the‐OH group and that additional interactions will be found in the adenosine deaminase active site.