Spectroscopic Evidence for Ternary Surface Complexes in the Lead(II)-Malonic Acid-Hematite System

Using extended X-ray absorption fine structure (EXAFS) and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) measurements, we examined the sorption of Pb(II) to hematite in the presence of malonic acid. Pb L(III)-edge EXAFS measurements performed in the presence of malonate indicate the presence of both Fe and C neighbors, suggesting that a major fraction of surface-bound malonate is bonded to adsorbed Pb(II). In the absence of Pb(II), ATR-FTIR measurements of sorbed malonate suggest the formation of more than one malonate surface complex. The dissimilarity of the IR spectrum of malonate sorbed on hematite to those for aqueous malonate suggest at least one of the sorbed malonate species is directly coordinated to surface Fe atoms in an inner-sphere mode. In the presence of Pb, little change is seen in the IR spectrum for sorbed malonate, indicating that geometry of malonate as it coordinates to sorbed Pb(II) adions is similar to the geometry of malonate as it coordinates to Fe in the hematite surface. Fits of the raw EXAFS spectra collected from pH 4 to pH 8 result in average Pb-C distances of 2.98 to 3.14 ?, suggesting the presence of both four- and six-membered Pb-malonate rings. The IR results are consistent with this interpretation. Thus, our results suggest that malonate binds to sorbed Pb(II) adions, forming ternary metal-bridging surface complexes. Copyright 2001 Academic Press.     

Phase diagrams and water activities of aqueous ammonium salts of malonic acid

Malonic acid has been observed in the free troposphere and as a component of tropospheric aerosol, among other dicarboxylic acids. These aerosols can uptake ammonia, which partially or completely neutralizes the acids. Therefore, the impact of ammoniated dicarboxylic acids on the phases that can exist in aerosols at atmospheric temperatures needs investigation. To that end, the low temperature, solid/liquid phase diagrams of ammonium hydrogen malonate/water, ammonium malonate/water, and triammonium hydrogen malonate/water have been investigated with differential scanning calorimetry and infrared spectroscopy of thin films. Results show that the order of increasing solubility is triammonium hydrogen malonate, ammonium hydrogen malonate, malonic acid, and ammonium malonate. We have also determined a hydrate may form in the ammonium malonate system and decompose below 240 K. We report water activities at the ice melting points for each system up to the respective eutectic concentrations, and find for a given mole fraction of water, increasing ammonium content leads to decreasing water activity coefficients.     

Oxidative Addition of Dimethyl Malonate to Styrenes Mediated by Cerium(Iv) Ammonium Nitrate: Some Novel Observations

The oxidative addition of dimethyl malonate to ring substituted styrenes leads to the formation of substituted dimethyl (2-oxo-2-phenylethyl) malonate and methyl 2-oxo-5-phenyltetrahydrofuran-3-carboxylate along with small amounts of substituted dimethyl [2-(nitrooxy)-2-phenylethyl] malonate and dimethyl 2-methoxy-2-phenylethyl) malonate. A tentative mechanism which supports the formation of these products is also presented.     

Carbon nucleophiles in the Mitsunobu reaction. Mono- and dialkylation of bis(2,2,2-trifluoroethyl) malonates

[formula: see text] Simple dialkyl malonate esters, for example diethyl malonate, exhibit relatively limited scope as carbon nucleophiles in the Mitsunobu dehydrative alkylation reaction. In contrast, bis(2,2,2-trifluoroethyl) malonate readily undergoes dehydrative alkylation with primary alcohols, and using only a slight excess of malonate gives monoalkylated product in good yield. Some secondary alcohols can also be employed, and bis(2,2,2-trifluoroethyl) malonates can be used in a second dehydrative alkylation to give dialkylated products in good to excellent yield.     

Reaction of isopropylidene malonate with N-arylidene-2-naphthylamines

It is shown that 4-aryl-2-oxo-1,2,3,4-tetrahydro-5,6-benzoquinolines are formed in the reaction of N-arylidene-2-naphthylamines with isopropylidene malonate. The reaction takes place with cleavage of the isopropylidene malonate ring and the production of carbon dioxide and acetone. The structure of the benzotetrahydroquinolines obtained were confirmed by identification of the compound obtained by sulfur dehydrogenation of the product of the reaction of isopropylidene malonate with arylidenenaphthylamine (aryl=phenyl) with an authentic sample of 1,2-dihydro-2-oxo-4-phenyl-5,6-benzoquinoline and of the reaction product (in which the aryl group was absent) with an authentic sample of 2-oxo-1,2,3,4-tetrahydro-5,6-benzoquinoline. The IR and PMR spectra data are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 973–976, July, 1977.     

Passivation of the calcite surface with malonate ion

Samples of polycrystalline calcite were impregnated with solutions of malonic acid of three concentrations (5 x 10(-2), 5 x 10(-3) , and 5 x 10(-4) M) and different pH values (6.00, 7.00, and 8.00). The impregnation was carried out at room temperature to evaluate the adsorption of malonate ion in the calcite surface to optimize the conditions for possible application on limestone and marble in cultural heritage materials. The affinity of the malonate ion was determined through the potentiometric measurement of the surface charge and the corresponding adsorbed amounts by titration, Raman spectroscopy, and small-angle X-ray scattering (SAXS). The results indicate effective adsorption of the malonate ion on the surface at a pH value close to the point of zero charge (pHpzc approximately 8.20) and changes in some surface morphological properties such as the pore shape and the pore size distribution. The presence of a malonate adsorptive layer on calcite generates an interface interaction potential that may influence the reaction and transport mechanisms within the medium.     

Mesomorphic properties of cyanobiphenyl dimers with a central malonate unit

A series of cyanobiphenyl dimers attached via alkoxy spacers to a central malonate were prepared, and the mesomorphic behaviour was studied by differential scanning calorimetry (DSC), polarised optical microscopy and X-ray diffraction (Wide-angle X-ray scattering and Small-angle X-ray scattering). Depending on spacer lengths and substitution of the malonate, nematic and smectic A mesophases with pronounced odd–even effect were observed. C-2-unsubstituted malonates formed nematic phases for chain lengths C₆–C₁₄, while C₁₂ and C₁₄ homologues displayed additional smectic A phases. In contrast, malonates with fluorinated tails at C-2 displayed exclusively smectic A phases. Remarkably, the X-ray diffraction profile of the smectic A phase of the C-2-unsubstituted C₁₂ malonate showed a fundamental (001) and the corresponding third-order (003) diffraction peak, but no (002) reflection. Using Fourier analysis, the diffraction pattern was converted to an electron density profile, which was in good agreement with the proposed packing model of the SmA mesophase based on a horseshow- or hairpin-like conformation of the malonate.     

Liquid-crystalline [60]fullerene-TTF dyads

[structure: see text] [60]Fullerene was functionalized with a TTF derivative and a bis-mesogenic fragment. The synthetic methodology was based on the addition of a malonate derivative to C60 (Bingel-type reaction). Both the malonate and dyad showed smectic B and A phases. The supramolecular organization within the smectic layers was of the monolayer type for the malonate and of the bilayer type for the fullerene derivative. In the latter case, the supramolecular organization was governed by the C60 unit.     

An ab initio mo study of calcium and magnesium complexes with malonate and formate

Quantum mechanical SCF calculations were performed on magnesium and calcium complexes of malonate and malonate/formate coordination. The calcium malonate structure is in substantial agreement with recent X-ray results on -ethylmalonate. The magnesium complexes are generally more tightly bound than calcium, although qualitatively, the calcium and magnesium structures are similar. Experimental binding results for divalent ions with malonates and EDTA are discussed in view of the current calculations.     

Nucleophilic addition to (3-methylpentadienyl)iron(1+) cations: counterion control of regioselectivity; application to the enantioselective synthesis of 4,5-disubstituted cyclohexenones

The regioselectivity of malonate addition to (3-methylpentadienyl)Fe(CO)3+ is controlled by the malonate-counterion association. The Li+ salt of malonate proceeds via C1 nucleophilic attack to afford the 1,3Z-diene complex 4a, while reaction of highly dissociated ion pair (i.e., Na+ or Li+/12-crown-4) salt proceeds at the C2 internal carbon to eventually afford cyclohexenone products 6. Reaction of 1a with the sodium salt of bis(8-phenylmenthyl)malonate proceeds with excellent diastereocontrol to afford a single diastereomeric cyclohexenone.     

Organocatalytic asymmetric conjugate addition of malonates to 3-nitro-2H-chromenes

The conjugate addition of malonates to 3-nitro-2H-chromenes has been studied in the presence of a number of chiral organocatalysts. A bifunctional thiourea-tertiary amine was found to be an efficient catalyst for the reaction. Good yields and enantioselectivities were obtained for a variety of substituted 3-nitro-2H-chromenes. Diethyl malonate and diisopropyl malonate were applicable for the reaction with lower yields and similar enantioselectivities. 1,3-Diphenylpropane-1,3-dione also provided the corresponding product, however with a low yield and enantioselectivity.     

Bis-amidocarbazolyl urea receptor for short-chain dicarboxylate anions

Urea receptor 1 based on two (1-amino-8-amido-3,6-dichloro)carbazole units shows a strong association with dicarboxylate anions such as oxalate, malonate and succinate guests through multiple hydrogen bonds from the carbazole, urea and amide NH groups. (1)H NMR complexation studies exhibit high values of association constants in DMSO-d(6). X-ray structures of the 1?:?1 complexes of 1 with oxalate and malonate as their ditetrabutylammonium salts were obtained. A modelling study of the complex of receptor 1 with succinate (as its diTBA salt) showed a more reduced geometric complementarity than its homologue malonate.     

Palladium-catalyzed reaction of nucleophiles with diacetates of allylic 1,1-diols

The reactions of allylic 1,1-diol diacetates (I) with carbanions under the catalysis of Pd(PPh₃)₄ were studied. Sodium diethyl malonate reacted with I to form an abnormal product resulting from the attack of the diethyl malonate carbanion on the carbonyl carbon of the acetoxy group, while sodium diethyl acetylmalonate gave the normal reaction products with high regioselectivity. The mechanisms of these reactions are discussed.     

Selective syntheses of novel polyether fullerene multiple adducts

We have applied a modified macrocyclic tether approach to control multiple additions to C60. The technique of 3He NMR was used to confirm the selective formation of specific C60 multiple adducts by the macrocyclic tether approach. An oligoglycol was used as a flexible linker to produce macrocyclic polyether-linked malonates 5, 6, 8, and 9 under solid-liquid PTC (phase-transfer-catalysis) conditions. The formation of a single C60 tris-adduct, 3, from macrocyclic malonate 1 and 3He@C60 was proven by 3He NMR. Similarly, multiple additions to C60 of macrocyclic polyether malonate 5 gave C60 bis-adduct 10 selectively, while the reaction of C60 with macrocyclic malonate 8 gave bis-adducts 11 and 12. A similar process with macrocyclic malonate 6 gave tris-adduct 13 with high selectivity as well. Saponification of these C60 multiple adducts gives the corresponding polyacids that are potentially useful in biological applications. Macrocyclic polyether fullerenes are a new class of ionophores, which could be interesting for molecular recognition and for the development of biosensors.     

Si-Tethered Bis- and Tris-Malonates for the Regioselective Preparation of Fullerene Multi-Adducts

Bis- and tris-malonates constructed around a silicon atom have been prepared by reaction of malonate derivatives bearing an alcohol function with di-tert-butylsilyl bis(trifluoromethanesulfonate) and tert-butyl(trichloro)silane, respectively. These compounds have been used for the regioselective bis- and tris-functionalization of C₆₀ under Bingel conditions. By changing the nature of the linker between the central Si atom and the reactive malonate groups, the malonate precursors have been optimized to produce specific bis- and tris-adducts with excellent regioselectivity. A complete understanding of the electronic and stereochemical factors governing the regioselectivity has been obtained by combining computational studies with a complete analysis of the by-products formed during the reactions of the Si-tethered tris-malonates with C₆₀. Finally, desilylation reactions of the resulting fullerene bis- and tris-adducts have been carried out to generate the corresponding acyclic fullerene bis- and tris-adducts bearing alcohol functions.     

Selective Cleavage of Carboxylic Esters in the Presence of Monosubstituted Malonates

Aliphatic carboxylic esters containing in the molecule a malonate moiety with an α-hydrogen undergo selective cleavage in the presence of potassium tertbutoxide in wet tetrahydrofuran.

     

Synthesis and structure of bis(tetraphenylantimony) malonate

Russian Chemical Bulletin - Bis(tetraphenylantimony) malonate was synthesized by the reaction of tetraphenylantimony bromide with silver malonate (the molar ratio was 2:1) in toluene. According to...     

Some interesting CH_2CH_3 spin systems in several diethyl malonate indene derivatives studied with NMR and molecular modeling

While studying the electrophilic cyclization of acetylenic malonates in synthesizing malonate indene derivatives with high regio and stereo-selectivity, we found that the CH2 and CH3 protons of two COOCH2CH3 groups in some diethyl malonate indene derivatives showed very interesting spin-spin coupling and signal multiplicity. To explain those phenomena, we synthesized several diethyl malonate indene derivatives, and then used 1H NMR spectra and molecular modeling to investigate the CH2CH3 spin system of thes...     

Synthesis and structures of malonate derivative-calix[4]arene conjugates

A series of novel malonate derivatives-calix[4]arene conjugates were synthesized through Knoevenagel condensation reaction, and the structures of these functionalized calix[4]arenes have been determined     

5-烃基-5-对甲苯磺酰氧基丙二酸亚异丙酯的合成

报道了利用羟基(对甲苯磺酰氧基)碘苯与5-烃基丙二酸亚异丙酯的反应合成5-烃基-5-对甲苯磺酰氧基丙二酸亚异丙酯的方法。提出了该反应的可能机理。