Mandelate Ion Research Articles

Polynuclear oxomolybdates(VI): Products of inadvertent oxidation of molybdenum(V) species

Unplanned oxidation of molybdenum(V) in the presence of carboxylic acid afforded three fully-oxidized polynuclear oxomolybdates. In very similar reaction mixtures, the initial oxidation state of the metal ion was retained and species with the frequently-encountered dinuclear {MoV(O)(μ2-O)2MoV(O)}2+ core formed. The chosen carboxylic acid contained either two COOH groups or another functional group, i.e., OH moiety. The carboxylic acid was introduced with the idea that with both of its functional groups engaged in coordination discrete clusters composed of the {MoV(O)(μ2-O)2MoV(O)}2+ units and the organic linkers would form. Reaction systems with dimethylmalonic acid (dmmH2) yielded two products, (Bu4N)2[Mo3O8(dmm)2] (1) with a trinuclear anion and [{MoV2O4Py2(dmmMe)}2(OCH3)2] (2) (Py = pyridine, dmmMe− = monomethyl dimethylmalonate ester) as the non-oxidized counterpart. The dmm2− ion engaged in coordination to Mo(VI) centers both carboxylate groups, whereas the dmmMe− ion coordinated to Mo(V) centers via its carboxylate moiety in a bidentate bridging mode. Reactions with mandelic (H2man) acid resulted in {(C6H5)4P}2[Mo4O10(OCH3)4Cl2] (3) with a tetranuclear core and in (PyH)3[MoV2O4Cl4(Hman)] (4). Only the non-oxidized compound 4 contains coordinated mandelate ion, whereas the role of the acid in the synthesis of 3 became that of a templating agent. (PyH)4[Mo8O26Py2] (5) with an octanuclear anion is a fully-oxidized compound obtained from the reaction mixture with succinic acid. The compounds were characterized by X-ray structure analysis, bond valence sum (BVS) calculations, IR vibrational and 1H NMR spectroscopy. The TG and DSC experiments were performed on fully-oxidized compounds. Powder X-ray diffraction has confirmed molybdenum(VI) oxide as the end product of the thermal decomposition of (Bu4N)2[Mo3O8(dmm)2] (1) and (PyH)4[Mo8O26Py2] (5) in the air atmosphere.

Novel gadolinium complexes in aqueous solution : characterization, identification and probable structures

In this work, we shall present the results of investigations on the interaction of the gadolinium ion (Gd 3+ ) with different chelation sites of mandelic acid and DL-serine (amino acid) formed in dilute solution for pH values between 5.50 and 7.50. The general formula of these new organometallic complexes is and (mandelate ions and: serine ions). These gadolinium complexes detected, are colorless and have no absorption band UV–visible. In this sense, we have used an analytical technique called « Indirect Photometry Detection (IPD) » have identified major di-nucleaire and tri-nuclear complexes of these acids. This technique allowed us to determine the composition and stabilities of complexes predominate in solution, giving for these colorless complexes a molar ration (2:2) and (3:2) for mandilic acid and serine acid respectively, and we have shown that the composition and stability constant depends on the acidity of the medium. To complement previous results and to propose probable structures for these new coloress complexes, IR and Raman spectroscopy have been conducted to identify the different chelation sites for theses ligands.

Dynamic helicity control of single-helical oligooxime metal complexes by coordination of chiral carboxylate ions

Helicity of single-helical metal complexes, [L1Zn3La]3+ and [L2Zn2La]3+, was dynamically controlled by coordination of chiral carboxylate ions such as mandelate ion. Spectroscopic investigation indicated that two chiral carboxylate ions contribute to the dynamic helicity control. In addition, the coordination of the carboxylate ions resulted in a nonlinear response in the dynamic helicity control.

Correlations of ion structure with multiple fragmentation pathways arising from collision‐induced dissociations of selected α‐hydroxycarboxylic acid anions

Under conditions of collision-induced dissociation (CID), anions of α-hydroxycarboxylic acids usually fragment to yield the distinctive hydroxycarbonyl anion (m/z 45) and/or the complementary product anion formed by neutral loss of formic acid (46 u). Further support for the known two-step mechanism, involving an ion-neutral complex for the formation of the hydroxycarbonyl anion from the carboxyl group, is herein provided by tandem mass spectrometric results and density functional theory computations on the glycolate, lactate and 3-phenyllactate ions. A fourth, structurally related α-hydroxycarboxylate ion, obtained by deprotonation of mandelic acid, showed only loss of carbon dioxide upon CID. Density functional theory computations on the mandelate ion indicated that similar energy inputs were required for a direct, phenyl-assisted decarboxylation and a postulated novel rearrangement to a carbonate ester, which yielded the benzyl oxide ion upon loss of CO2. Rearrangement of the glycolate ion led to expulsion of carbon monoxide, whereas the 3-phenyllactate ion showed the loss of water and formation of the benzyl anion and the benzyl radical as competing processes. The fragmentation pathways proposed for lactate and 3-phenyllactate are supported by isotopic labeling. The relative computed energies of saddle points and product ions for all proposed fragmentation pathways are consistent with the energies supplied during CID experiments and the observed relative intensities of product ions. The diverse reaction pathways characterized for this set of four α-hydroxycarboxylate ions demonstrate that it is crucial to understand the effects of structural variations when attempting to predict the gas-phase reactivity and CID spectra of carboxylate ions.

Relative reactivity of phenylboronic acid to phenylboronate ion toward L-lactate and mandelate at physiological pH

Abstract Kinetic studies were performed on the reactions of phenylboronic acid with L -lactic acid and mandelic acid in acidic aqueous and alkaline solutions in order to specify reactive species in these reactions. It was confirmed that the diprotonated ligand (H 2 L: L -lactic acid or mandelic acid) is less reactive than the monoprotonated ligand (HL − : L -lactate ion or mandelate ion), which made possible direct determination of the rate constants of phenylboronic acid (PhB(OH) 2 ) and its conjugate base, phenylboronate ion (PhB(OH) 3 − ). It was found that PhB(OH) 2 is more reactive than PhB(OH) 3 − . On the basis of kinetic results, it was concluded that the most reactive species are PhB(OH) 2 and HL − at physiological pH 7.4, so the reaction in the boronic acid-based sensor for L -lactate mainly would occur between these species.

Optically active polypyrroles containing chiral dopant anions

A reexamination of the electropolymerization of pyrrole in the presence of (+)- and (–)-camphorsulfonic acid (HCSA) has shown that, contrary to a recent report, the deposited PPy·HCSA films do not possess macroasymmetry in their polypyrrole chains. In contrast, similarly deposited PPy·(+)-tart, PPy·(–)-tart, PPy·(+)-mand and PPy·(–)-mand films (tart = tartrate ion; mand = mandelate ion) exhibit weak circular dichroism bands in the visible region, confirming partial chiral induction in their polypyrrole backbones due to the presence of the chiral dopant anions during the electropolymerizations. The much weaker chiral induction compared to related electropolymerizations of aniline is ascribed to the absence of polar groups on the polypyrrole backbone to facilitate interaction with the chiral dopant.

(R,S)-1-Phenylethylammonium (R,S)-Mandelate

The asymmetric unit of the title compound, C 8 H 12 N + .C 8 H 7 O 3 - contains two 1-phenylethylammonium cations with opposite configurations and two (S)-mandelate anions (α-hydroxybenzeneacetate). The ions are shown to be nearly related by a pseudo inversion centre. This gives rise to an unusual conformation of one of the (S)-mandelate ions. An extensive hydrogen-bond system connects the ions in a similar way to the hydrogen-bond patterns found in (S)-1-phenylethylammonium (S)-mandelate and (R)-mandelate

Optical resolution through diastereomeric salt formation: the crystal structures of cinchoninium (R)-mandelate and cinchoninium (S)-mandelate at low temperature

The crystal structures of the diastereomeric salts formed between cinchonine and mandelic acid have been analysed. The more soluble of the two salts is cinchoninium (S)-mandelate, C19H23N20 +.C8H703--, Mr = 446.55, monoclinic, P21, T= 110 (1) K, a = 11.2478(10), b=7.0880(6), c=14.684(2) A, /3= 99.068 (7) °, V = 1156.0 (4)/~3, Z = 2, Ox = 1.283 g cm -3, A(Cu Ka) = 1.54184 A, # = 6.57cm-1, F(000)=476, R=0.029 for 2338 observed reflections. The less soluble salt is cinchoninium (R)-mandelate, CI9H23N20 +.CSH7Of, Mr = 446.55, orthorhombic, P212121, T = 122.0 (5)K, a = 12.078 (4), b = 17.423 (2), c = 22.136 (4),~, V= 4658 (3) A 3, z = 8, Dx = 1.273 gcm- 3, A(Cu Ka) = 1.54184 ,~, /1, = 6.52 cm- ~, F(000) = 1904, R = 0.055 for 4125 observed reflections. In the (R)-mandelate salt one of the two independent cinchoninium cations displays disorder of the --CH=CH2 moiety. Apart from variations in the conformation of the vinyl group the cinchoninium cations are alike. The difference in conformation of the (R)- and (S)mandelate ions can be related to differences in the hydrogen-bonding systems. Interionic interactions in the S salt stabilize it relative to the R salt. The differences in the melting enthalpies and entropies of the two diastereomeric salts are related to their structural differences.

Generation and study of enols and other reactive species

Abstract

Chemistry, structure and bonding in diruthenium(II) tetracarboxylates

Ru{sub 2}(O{sub 2}CCH{sub 3}){sub 4}Cl reacts with L-mandelic acid (Hmand) to convert 50% of the ruthenium to Ru{sub 2}(mand){sub 4}(H{sub 2}O){sub 2} (2) and 50% to the accompanying disproportionation product, (Ru{sub 3}O(mand){sub 6}(H{sub 2}O){sub 3}){sup +}. The Ru{sub 2}(II,II) mandelate has been isolated and structurally characterized as Ru{sub 2}(mand){sub 4} {times} 2H{sub 2}O, which crystallizes in space group P2{sub 1} with the following unit cell parameters: a = 7.610 (2) {angstrom}, b = 32.181 (7) {angstrom}, {beta} = 90.28 (2) {degree}, V = 3,328 (3) {angstrom}{sup 3}, Z = 4. Two independent but essentially identical molecules having mandelate ions of the correct absolute chirality were found. The Ru-Ru distances are 2.266 (1) and 2.256 (1) {angstrom}; the water molecules are axially coordinated with a mean Ru-O distance of 2.35 {angstrom}. This is the first time a Ru{sub 2}(II,II) compound has been obtained directly, on a preparative scale from a Ru{sub 2}(II,III) compound.

Bonding Trends in Lanthanide Mandelates

AbstractThe lanthanide mandelates have been prepared by reacting the lanthanide hydroxides with mandelic acid (HL). The coordination number in these compounds has been discussed on the basis of analytical, infrared and electronic spectral, and thermal data. The mandelates have the general formula, LnL3.nH2O, where n3 for LnLa, Pr, Nd and Sm, and n=2 for LnGd, Dy, Br, Yb and Y. The infrared spectral data reveal that the mandelate ion is coordinated to the lanthanide ions in a bidentate fashion through the oxygen atoms of the carboxylate and the hydroxyl groups. The antisymmetric COO−, the δ OH, and the Ln‐O frequencies in the mandelates show a linear relationship with the ionic radius of the lanthanide ions. The infrared spectral and thermal data afford evidence of the coordination of all the molecules of water to the lanthanide ions. Hence, coordination numbers nine and eight have been assigned to the two sets of mandelates. This conclusion is supported by a study of the shapes of the hypersensitive transitions in the electronic absorption spectra of Nd and Br mandelates. The electronic spectra also suggest that the bonding in these compounds is predominantly ionic.

Oxidation of Mandelic Acid by Os(VIII)

Abstract Mandelic Acid, Osmium(VIII) In the reaction between mandelic acid and Os(VTII), the rate of Os(VIII) disappearance was found to be proportional to the concentration of mandelate ion and Os(VIII). At low and high hydroxyl ion concentration the rate shows second and zero order dependence respectively. The reaction was studied at different temperatures and various activation parameters ⊿E, PZ, ⊿S* etc. were evaluated.

Kinetics and Mechanism of Os(VIII) Catalysed Oxidation of Mandelate Ion by Alkaline Ferricyanide

The kinetics of the reaction between alkaline ferricyanide and mandelic acid catalysed by [Os (VIII) ] has beeen studied. The rate of ferricyanide disappearance was found to be proportional to the concentration of mandelate ion and Os (VIII), but independent of the concentration of ferricyanide. Within a limited concentration range of hydroxyl ion [ [OH-1] < 0.25 M] the rate varies directly as the [OH⁻]. Effects of SO4 -2, ΝO3 -1NO3 -1 and temperature on the rate were studied. ΔΕ, PZ, AS* etc. were evaluated. Mechanism of oxidation of mandelic acid based on the formation of Os (VIII) acid anion complex is suggested.

Circular Dichroism of Co(II) and Ni(II) Complexes with (-)-Mandelate Ions in Aqueous Solution.

Circular Dichroism of Co(II) and Ni(II) Complexes with (-)-Mandelate Ions in Aqueous Solution.

Kinetics and mechanism of the osmium-tetroxide-catalysed oxidation of mandelate ion by hexacyanoferrate(III) ion

The osmium-tetroxide-catalysed oxidation of mandelate ion by hexacyanoferrate(111) ion has been studied kinetically. The reaction rate has been found to be independent of hexacyanoferrate(111) ion while the order with respect to both osmium tetroxide and mandelate ion comes out to be unity. The reaction rate follows first-order kinetics at low hydroxyl ion concentration and becomes zero order at higher concentrations. The course of the reaction has been considered to proceed through the formation of an activated mandelate-OsO4, complex which decomposes in alkaline medium giving reduced osmium(V1) followed by a fast oxidation by hexacyanoferrate(111) ion. The probable course of the reactions is also described with the help of its oxidation product, benzoic acid.

A Polarimetric Investigation of the Complex Formation between Zinc and Mandelate Ions.

A Polarimetric Investigation of the Complex Formation between Zinc and Mandelate Ions.