- Investigation of Radical Reactions Important in the Gyoergyi-Turanyi-Field Model of the Belousov-Zhabotinskii Reaction
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In the Gyoergyi-Turanyi-Field (GTF) model of the Belousov-Zhabotinskii (BZ) reaction, malonyl radicals (MA.) and bromomalonyl radicals (BrMA.) are assumed to be important intermediates.The hydrogen abstraction reactions MA. + BrMA -> MA + BrMA. (a) and BrMA. + MA -> BrMA + MA. (b) (MA, malonic acid; BrMa, bromomalonic acid) transfer from free-radical nature of the malonyl species to the bromomalonyl species and vice versa.The rates of these two reactions determine in part the relative importance of these radical intermediates.Another key radical reaction is BrMA. + Ce4+ + H2O -> BrTTa + Ce3+ (c) (BrTTA, bromotartronic acid), which is a source of Br- through decomposition of BrTTA in the model.It has been deduced from ESR and spectrophotometric experiments that reactions a-c do not contribute to the chemistry of the BZ reaction.Numerical integration of the GTF rate equations, omitting reactions a-c, shows no oscillation in BZ systems with high initial concentrations of BrMA.Experimentally, these systems exhibit oscillations with no induction period.
- Foersterling, Horst-Dieter,Stuk, Linda
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- MALONATED ANTHOCYANINS IN MALVACEAE: MALONYLMALVIN FROM MALVA SYLVESTRIS
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A new anthocyanin, malvidin 3-(6"-malonylglucoside)-5-glucoside has been characterized in both wild and cultivated forms of Malva sylvestris.Thus the classic source of the anthocyanin, malvin, actually contains the pigment in the flowers in malonated form.Malonated anthocyanins were also detected in Althaea rosea, Lavatera olbia and a Sphaeralcea sp. but they were not present in five other species in the family. - Keywords: Malva sylvestris; Malvaceae; mallow; flowers; malvidin 3-(6"-malonylglucoside)-5-glucoside; malvin.
- Takeda, Kosaku,Enoki, Shigeki,Harborne, Jeffrey B.,Eagles, John
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- An unusual acylated malvidin 3-glucoside from flowers of Impatiens textori Miq. (Balsaminaceae)
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Acylated malvidin 3-glucoside was isolated from the purple flowers of Impatiens textori Miq. as a major anthocyanin component along with malvidin 3-(6″-malonyl-glucoside). Its structure was elucidated to be malvidin 3-O-[6-O-(3-hydroxy-3-methylglutaryl)-β
- Tatsuzawa, Fumi,Saito, Norio,Mikanagi, Yuki,Shinoda, Koichi,Toki, Kenjiro,Shigihara, Atsushi,Honda, Toshio
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- Exploring the Promiscuous Enzymatic Activation of Unnatural Polyketide Extender Units in Vitro and in Vivo for Monensin Biosynthesis
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The incorporation of new-to-nature extender units into polyketide synthesis is an important source for diversity yet is restricted by limited availability of suitably activated building blocks in vivo. We here describe a straightforward workflow for the biogenic activation of commercially available new-to-nature extender units. Firstly, the substrate scope of a highly flexible malonyl co-enzyme A synthetase from Streptomyces cinnamonensis was characterized. The results were matched by in vivo experiments in which the said extender units were accepted by both the polyketide synthase and the accessory enzymes of the monensin biosynthetic pathway. The experiments gave rise to a series of predictable monensin derivatives by the exploitation of the innate substrate promiscuity of an acyltransferase and downstream enzyme functions.
- Grote, Marius,Schulz, Frank
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- Diverse structural assemblies of a series of ninhydrin derivatives: Quantitative analyses from experimental and theoretical studies
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Three ninhydrin derivatives (2–4) have been synthesized where the reaction of ninhydrin with Meldrum's acid yielded [3.3.3] propellanoid (2) and ethyl 2,2-bis (1,3-dioxo-2,3-dihydro-1H-inden-2-yl)acetate (3) while with malononitrile yielded a spiroindenopyran (4). The products being crystalline in nature and are characterized by single crystal X-ray diffraction in addition to other spectroscopic studies. X-ray crystallography reveals that solid-state structure of the title compounds exhibits C?H···π, π?π and lone-pair(l.p)···π interactions in building supramolecular assemblies. Indeed, compound (2) was stabilized through extended supramolecular C?H···π/π?π/π···H?C network whereas compounds (3) and (4) are stabilized through lone-pair (l.p)···π and π?π interaction respectively. The diverse intermolecular interactions via Hirshfeld surface analysis enables quantitative contributions to the crystal packing that exposes the similarities and differences in the interactions experienced by each compound. The distinctive energy frameworks have been calculated for individual molecules and the interaction energies suggest that the contacts are largely dispersive in nature. The binding energies associated with the non-covalent interactions observed in the crystal structures have been calculated using theoretical DFT calculations. Finally, the interplay between the interactions have been characterized by Bader's theory of “atoms-in-molecules” (AIM).
- Hundal, Geeta,Kapoor, Kamal K.,Mahajan, Sheena,Saini, Yeshwinder,Seth, Saikat Kumar
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- Kinetic modeling of malonylgenistin and malonyldaidzin conversions under alkaline conditions and elevated temperatures
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The conversion and degradation of malonylglucosides were kinetically characterized under elevated pH/heat conditions. Malonylgenistin and malonyldaidzin were heated at 60, 80, and 100°C and pH values of 8.5, 9, and 9.5. A simple kinetic model was developed, which adequately predicted the conversion and degradation reactions. The conversion and degradation rates increased as temperature and pH increased. The rates of conversion of both malonylglucosides into their respective β-glucosides were comparable under all pH/heat treatments. However, at 100°C, the rates of degradation of malonyldaidzin were approximately double those of malonylgenistin, under all pH treatments. When malonlydaidzin was heated at 100°C and pH 9.5, degradation of the produced daidzin occurred. Therefore, an alternative kinetic model was developed to better predict the conversion and degradation of malonyldaidzin occurring at 100°C and pH 9.5. The models developed provide soy food manufacturers with guidelines for better control of the profile and level of isoflavones.
- Vaidya, Nirupama A.,Mathias, Kevin,Ismail, Baraem,Hayes, Kirby D.,Corvalan, Carlos M.
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- Enols derived from malonic acids as intermediates in nitrosation and halogenation
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Malonic acid, methylmalonic acid, ethylmalonic acid and phenylmalonic acid react with electropholic nitrosating agents and also with bromine and iodine via their corresponding enol or enolate forms. In most cases it is possible to make either the enolisation or reaction of the enol rate-limiting by a suitable choic of reactant concentrations and reactivity. The enolisation rate constants agree resonably well with literature values where they exist. We propose minimum figures of 1.0 x 10-8 and 1.6 x 10-8 respectively for K(E) the enolisation equilibrium constant for malonic acid and methylmalonic acid. The kinetic term second order in [malonic acid] or its derivatives (when enolisation is rate limiting) has been shown to arise from a base catalysed component to the reaction brought about by the malonate ion, which dominates at pH values greater than ca. 3.
- Williams,Graham
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- Design of bisquinolinyl malonamides as Zn2+ ion-selective fluoroionophores based on the substituent effect
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A series of malonamides possessing two quinoline moieties were synthesized and characterized as fluoroionophores for the Zn2+ ion. We focused on the relationship between the substituents introduced to the C2-position of the malonamides and their Zn2+ ion-selectivity, exploiting the structural effect of the substituents in the design of the fluoroionophores with high selectivity. The substituents introduced to the malonamides were the methyl, benzyl and naphthalenylmethyl groups. In dimethyl sulfoxide solvent, all substituted bisquinolinyl malonamides showed excellent fluorescence sensing for the Zn2+ ion, while unsubstituted bisquinolinyl malonamide 1 displayed ratiometric sensing for the Co2+ ion. N,N′-Bis(8-quinolyl)-2-methyl-2-naphthalenylmethyl malonamide 4 exhibited the highest Zn2+ ion-selectivity against the Cd2+ ion. Although the substituents introduced into the C2-position are spatially distant from the quinoline recognition moiety, this study indicated that they greatly influenced the ion selectivities of the bisquinolinyl malonamides. Furthermore, it was demonstrated that visible fluorescence analyses could be performed on malonamide 4.
- Moriuchi-Kawakami, Takayo,Kawata, Keita,Nakamura, Sho,Koyama, Yoshiaki,Shibutani, Yasuhiko
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- Photo-Induced Disproportionation of Iodomalonic Acid
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The stoichiometry, equilibrium, and kinetics of the photo-induced disproportionation of iodomalonic acid to I-, I2, and tartronic acid have been studied by means of spectrophotometry and iodide selective electrode at 20.0 +/- 0.2 deg C, pH 2.0 - 4.0.At pH > 2.9, only I- and HOCH(COOH)2 are detected as major products and the reaction reaches 100percent conversion.At pH I. + .CH(COOH)2, (M2) I2 + hν 2I..While both reactions are sensitive to UV light, only M2 can be affected by visible light. (M1) and (M2) are considered to initiate a chain reaction sequence in which I. radicals oxidize iodomalonic acid.Dual effects of reaction products on the reaction rate have been observed: while iodine increases the efficiency of visible light and accelerates the reaction, malonic acid inhibits the photo-decomposition by mediating the recombination of I. radicals to I2.
- Rabai, Gyula,Hanazaki, Ichiro
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- Experimental and mechanistic investigation of an iodomalonic acid-based Briggs-Rauscher oscillator and its perturbations by resorcinol
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Classic Briggs-Rauscher oscillators use malonic acid (MA) as a substrate. The first organic product is iodomalonic acid. Iodomalonic acid (IMA) can serve as a substrate also; thus, the first product in that case is diiodomalonic acid (I2MA). Nonoscillating iodination kinetics can be followed by absorbance at 462 nm in acidic KIO3 so long as IMA is in substantial excess over [I2]. At 25 °C, simulations lead to the two most important rate laws, and related rate constant estimates are reported. I 2MA eventually decomposes by unknown processes, but I2, O2, H2O2, and Mn2+ speed up that decomposition, liberating most of the iodine back to the solution. Resorcinol is an effective inhibitor of oscillations both in MA oscillators and in IMA oscillators. Response of an IMA oscillator to varying amounts of resorcinol is shown herein and is similar to that for MA-based oscillators. The inhibitory effect of resorcinol is diminished by addition of IMA to a MA-based oscillator. The iodination reaction between IMA and resorcinol is too slow (0.043 M -1 s-1) to account for the decreased inhibitory effectiveness of resorcinol. Rather, the decomposition of I2MA is responsible for the inhibition decrease.
- Cervellati, Rinaldo,Greco, Emanuela,Furrow, Stanley D.
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- Degradation of 2,5-dihydroxy-1,4-benzoquinone by hydrogen peroxide under moderately alkaline conditions resembling pulp bleaching: A combined kinetic and computational study
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2,5-Dihydroxy-1,4-benzoquinone (DHBQ) is one of the key chromophores occurring in all types of aged cellulosics. This study investigates the mechanism of H2O2 degradation of DHBQ under conditions relevant to pulp bleaching (3.0% H2O2, NaOH, pH 10), to obtain insights useful for improved pulp processing. DHBQ is degraded quantitatively into malonic acid with an activation energy (Ea) of 16.1 kcal/mol and activation entropy (ΔaS) of ～28 cal/mol·K. Higher concentrations of sodium cations increase the reaction rate. Theoretical computations indicate the formation of an intermediate IO having an O-O bridge between C-2 and C-5 of the 1,4-cyclohexadione structure. IO undergoes O-O homolysis to form a biradical Bt, which is fragmented into malonate anions. The calculated Ea (17.8 kcal/mol) agrees well with the experimental one. Coordination of Na+ to IO and Bt decreases their energies and enhances the O-O homolysis rate, which is consistent with the acceleration by sodium cation and the negative ΔaS. The homolysis of IO is much favored over that of the neutral counterpart, with the unpaired electrons of Bt being stabilized by the geminal anionic oxygen. This difference in the stability of the intermediates translates into significant variations in the reaction rate and the product distribution between pH 10 and neutral/acidic conditions.
- Hosoya, Takashi,Rosenau, Thomas
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- PRUNASIN-6'-MALONATE, A CYANOGENIC GLUCOSIDE FROM MERREMIA DISSECTA
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The cyanogenic glucosides prunasin and 6'-O-malonylprunasin have been isolated from the leaves of Merremia dissecta.Malonylprunasin is the first example of a malonyl conjugate of the cyanogenic glycosides. - Keywords: Merremia dissecta; Convolvulaceae; prunasin, malonylprunasin; cyanogenesis.
- Nahrstedt, Adolf,Jensen, Pia Skjottgaard,Wray, Victor
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- Single particle analysis of secondary organic aerosols formed from 1,4-cyclohexadiene ozonolysis using a laser-ionization single-particle aerosol mass spectrometer
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Real-time analysis of secondary organic aerosol (SOA) particles formed from 1,4-cyclohexadiene (CHD) ozonolysis in a smog chamber was performed using a laser-ionization single-particle aerosol mass spectrometer (LISPA-MS). The instrument can be used to obtain both the size and chemical compositions of individual aerosol particles with a high time-resolution (≈2 s at the maximum). Both positive- and negative-ion mass spectra can be obtained by changing the voltage polarity of the instrument. The negative-ion spectra of the SOA particles provided important information about the chemical compositions of the SOA particles. In the negative-ion spectra, intense mass peaks were determined to correspond to ions with carboxyl and aldehyde groups. The signal intensities of the intense mass peaks from compounds with carboxyl groups were higher than those from compounds with aldehyde groups as a function of the particle size. The peaks suggest that the SOA particles contain more oxygenated organic compounds as the particle size increases, namely, the chemical compositions of the SOA particles vary as a function of the particle size. We demonstrated that the real-time single-particle analysis of SOA particles by using the LISPA-MS technique can be used to clarify the formation and transformation processes of SOA particles in smog chambers.
- Narukawa, Masahiro,Matsumi, Yutaka,Matsumoto, Jun,Takahashi, Kenshi,Yabushita, Akihiro,Sato, Kei,Imamura, Takashi
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- Doxycycline degradation by the oxidative Fenton process
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Doxycycline is a broad-spectrum tetracycline occurring in domestic, industrial, and rural effluents, whose main drawback is the increasing emergence of resistant bacteria. This antibiotic could be degraded by the so-called Fenton process, consisting in the oxidation of organic pollutants by oxygen peroxide (H in the presence of Fe2+. Experiments were performed according to an experimental Rotational Central Composite Design to investigate the influence of temperature (0-40.0°C), Hconcentration (100-900 mg/L), and Fe2+ concentration (5-120 mg/L) on residual doxycycline and total organic carbon concentrations. Whereas the final residual doxycycline concentration ranged from 0 to 55.8 mg/L, the oxidation process proved unable to reduce the total organic carbon by more than 30%. The best operating conditions were concentrations of Hand Fe2+ of 611 and 25 mg/L, respectively, and temperature of 35.0°C, but the analysis of variance revealed that only the first variable exerted a statistically significant effect on the residual doxycycline concentration. These results suggest possible application of this process in the treatment of doxycycline-containing effluents and may be used as starting basis to treat tetracycline-contaminated effluents.
- Borghi, Alexandre A.,Silva, Milena F.,Al Arni, Saleh,Converti, Attilio,Palma, Mauri S. A.
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- Ozonolysis of α-angelica lactone: a renewable route to malonates
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Industrially relevant intermediates such as malonic acid, malonates and 3-oxopropionates can be easily accessed by ozonolysis of α-angelica lactone, derived from the platform chemical levulinic acid. The roles of the solvent and of the quenching conditions are of key importance for the outcome of the reaction.
- Dell’Acqua, Andrea,Stadler, Bernhard M.,Tin, Sergey,Wille, Lukas,de Vries, Johannes G.
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supporting information
p. 10524 - 10527
(2021/10/19)
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- Hydrolysis of amides to carboxylic acids catalyzed by Nb2O5
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Hydrolysis of amides to carboxylic acids is an industrially important reaction but is challenging due to the difficulty of cleaving the resonance stabilized amidic C-N bond. Twenty-three heterogeneous and homogenous catalysts were examined in the hydrolysis of acetamide. Results showed that Nb2O5was the most effective heterogeneous catalyst with the greatest yield of acetic acid. A series of Nb2O5catalysts calcined at various temperatures were characterized and tested in the hydrolysis of acetamide to determine the effects of crystal phase and surface properties of Nb2O5on catalytic performance. The high catalytic performance observed was attributed mainly to the facile activation of the carbonyl bond by Lewis acid sites that function even in the presence of basic inhibitors (NH3and H2O). The catalytic studies showed the synthetic advantages of the present method, such as simple operation, catalyst recyclability, additive free, solvent free, and wide substrate scope (>40 examples; up to 95% isolated yield).
- Siddiki,Rashed, Md. Nurnobi,Touchy, Abeda Sultana,Jamil, Md. A. R.,Jing, Yuan,Toyao, Takashi,Maeno, Zen,Shimizu, Ken-Ichi
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p. 1949 - 1960
(2021/03/26)
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- Electrochemical oxidation of diclofenac on CNT and M/CNT modified electrodes
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The electrochemical oxidation of diclofenac (DCF), a non-steroidal anti-inflammatory drug considered as an emerging pollutant (frequently detected in wastewater), was investigated on CNT, Pt/CNT and Ru/CNT modified electrodes based on Carbon Toray in aqueous media. The electroreactivity of DCF on these modified electrodes was studied using cyclic voltammetry and the kinetic parameters were calculated from the scan rate study. Cyclic voltammograms show several oxidation processes, which confirm the interaction between DCF and the catalyst surface necessary for direct oxidation processes. Constant potential electrolysis of DCF was carried out on carbon nanotubes (CNT) and metal supported CNT (M/CNT) modified electrodes, in 0.1 M NaOH and 0.1 M Na2CO3/NaHCO3buffer media. The highest DCF conversion (88% after 8 h of electrolysis) was found in carbonate buffer medium, for Ru/CNT, while the best carbon mineralization efficiency (corresponding to 48% of the oxidized DCF) was obtained on Pt/CNT modified electrode in 0.1 M NaOH medium. The products of the electrolyses were identified and quantified by HPLC-MS, GC-MS, HPLC-UV-RID and IC. The results show the presence of some low molecular weight carboxylic acids, confirming the cleavage of the aromatic rings during the oxidation process.
- Ferreira, M.,Figueiredo, J. L.,Fonseca, A. M.,Güney, S.,Ku?niarska-Biernacka, I.,Neves, I. C.,Parpot, P.,Pereira, M. F. R.,Soares, O. S. G. P.
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p. 12622 - 12633
(2021/07/25)
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- METHOD FOR PREPARATION OF DIESTER DERIVATIVES OF MALONIC ACID
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Methods for the preparation of bio-based malonic acid and diester derivatives of malonic acid are provided. The disclosed methods produce diester derivatives of malonic acid with fewer impurities, which is useful for many industrial processes. The diester derivatives of malonic acid can be purified from existing sources of malonic acid, or from malonic acid made from a renewable carbon source.
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- Macrolactam Synthesis via Ring-Closing Alkene-Alkene Cross-Coupling Reactions
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Reported herein is a practical method for macrolactam synthesis via a Rh(III)-catalyzed ring closing alkene-alkene cross-coupling reaction. The reaction proceeded via a Rh-catalyzed alkenyl sp2 C-H activation process, which allows access to macrocyclic molecules of different ring sizes. Macrolactams containing a conjugated diene framework could be easily prepared in high chemoselectivities and Z,E stereoselectivities.
- Goh, Jeffrey,Loh, Teck-Peng,Maraswami, Manikantha
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supporting information
p. 9724 - 9728
(2020/12/21)
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- Carbon nanotubes as catalysts for wet peroxide oxidation: The effect of surface chemistry
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Three magnetic carbon nanotube (CNT) samples, named A30 (N-doped), E30 (undoped) and E10A20 (selectively N-doped), synthesized by catalytic chemical vapor deposition, were modified by introducing oxygenated surface groups (oxidation with HNO3, samples CNT-N), and by heat treatment at 800 °C for the removal of surface functionalities (samples CNT-HT). Both treatments lead to higher specific surface areas. The acid treatment results in more acidic surfaces, with higher amounts of oxygenated species being introduced on N-doped surfaces. Heat-treated samples are less hydrophilic than those treated with nitric acid, heat treatment leading to neutral or basic surfaces, only N-quaternary and N-pyridinic species being found by XPS on N-doped surfaces. These materials were tested in the catalytic wet peroxide oxidation (CWPO) of highly concentrated 4-nitrophenol solutions (4-NP, 5 g L?1) at atmospheric pressure, T = 50 °C and pH = 3, using a catalyst load of 2.5 g L?1 and the stoichiometric amount of H2O2 needed for the complete mineralization of 4-NP. The high temperature treatment enhanced significantly the activity of the CNTs towards CWPO, evaluated in terms of 4-NP and total organic carbon conversion, due to the increased hydrophobicity of their surface. In particular, E30HT and E10A20HT were able to remove ca. 100% of 4-NP after 8 h of operation. On the other hand, by treating the CNTs with HNO3, the activity of the less hydrophilic samples decreased upon increasing the concentration of surface oxygen-containing functionalities, whilst the reactivity generated inside the opened nanotubes improved the activity of the highly hydrophilic A30 N.
- Martin-Martinez, Maria,Machado, Bruno F.,Serp, Philippe,Morales-Torres, Sergio,Silva, Adrián M.T.,Figueiredo, José L.,Faria, Joaquim L.,Gomes, Helder T.
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p. 332 - 340
(2019/03/17)
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- Directly Microwave-Accelerated Cleavage of C?C and C?O Bonds of Lignin by Copper Oxide and H2O2
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Model erythro, phenolic, and nonphenolic lignin β-O-4 dimer compounds are treated with copper oxide and H2O2 at the electronic field maximum position of a single-mode 2.45 GHz microwave system equipped with a cavity resonator. The products obtained through microwave heating and oil-bath heating with the same reaction vessel and temperature profile are quantitatively compared. Dimer degradation is found to proceed through consecutive elementary reactions. The phenolic dimer is dehydroxylated and this is followed by the spontaneous cleavage of Cα?Cβ and C?O?C bonds to produce guaiacol, vanillin, and vanillic acid. The reaction of the nonphenolic dimer produces veratric acid, veratraldehyde, and guaiacol. Microwave irradiation accelerates cleavage of the side chain and the oxidation of vanillin to vanillic acid. However, no acceleration of veratraldehyde oxidation to veratric acid or aromatic ring cleavage to produce dicarboxylic acids is observed. The selective acceleration of elementary reactions during the degradation of model lignin compounds indicates that microwaves interact with reaction intermediates that are sensitive to electromagnetic waves.
- Qu, Chen,Ito, Keigo,Katsuyama, Isamu,Mitani, Tomohiko,Kashimura, Keiichiro,Watanabe, Takashi
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p. 4510 - 4518
(2020/05/18)
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- Molecularization of Bitter Off-Taste Compounds in Pea-Protein Isolates (Pisum sativum L.)
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Activity-guided fractionations, combined with taste dilution analyses (TDA), were performed to locate the key compounds contributing to the bitter off-taste of pea-protein isolates (Pisum sativum L.). Purification of the compounds perceived with the highe
- Gl?ser, Peter,Dawid, Corinna,Meister, Stefanie,Bader-Mittermaier, Stephanie,Schott, Michael,Eisner, Peter,Hofmann, Thomas
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p. 10374 - 10387
(2020/10/26)
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- Expeditious and sustainable two-step synthesis of sinapoyl-l-malate and analogues: Towards non-endocrine disruptive bio-based and water-soluble bioactive compounds
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Faced with the increasing demand from both the cosmetic industries and consumers for bio-based, safe and natural skin products, sinapoyl-l-malate, widely described for its UV protection in plants, appears to be an excellent alternative to substitute chemical filters in sunscreens. Unfortunately, the only synthetic routes described in the literature were not only tedious but also exhibit a strong negative environmental impact, thus seriously limiting the industrialization and commercialization of sinapoyl-l-malate. Herein, a shorter and greener synthetic pathway involving Meldrum's acid opening with unprotected naturally occurring hydroxy acids and its subsequent Knoevenagel-Doebner condensation with biomass-derived p-hydroxybenzaldehydes was designed and developed. This two-step procedure, whom sustainability has been assessed using green metrics (atom economy (AE), process atom economy (PAE), E-factor and LCA), is a great alternative to the already reported procedures and allows the access to sinapoyl-l-malate and several analogs in average to good yield. The study of the anti-UV properties, stability against UV radiation, radical scavenging and antimicrobial activities of the targets revealed attractive properties as photostable UV filters, antioxidants and preservatives. Moreover, the water solubility brought by the free carboxylic acids facilitates the incorporation of these molecules in cosmetic formulations. Finally, their innocuousness toward endocrine disruption was demonstrated.
- Peyrot, Cédric,Mention, Matthieu M.,Fournier, Robin,Brunissen, Fanny,Couvreur, Julien,Balaguer, Patrick,Allais, Florent
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supporting information
p. 6510 - 6518
(2020/11/09)
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- Catalytic oxidative dehydrogenation of malic acid to oxaloacetic acid
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Here we report the oxidative dehydrogenation of malic acid to oxaloacetic acid, a key precursor in the fabrication of amino acids, over Pt-Bi/C catalysts. Under optimized conditions, we discovered that OAA was selectively produced with up to 60% conversion (i.e. 60% yield). The recurrent unwanted decarboxylation of OAA to pyruvic acid was circumvented by successfully conducting the catalytic reaction at 25 °C. A comparison with the classical Fenton oxidation reaction is discussed.
- Drif, Asmaa,Pineda, Antonio,Morvan, Didier,Belliere-Baca, Virginie,De Oliveira Vigier, Karine,Jér?me, Fran?ois
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supporting information
p. 4604 - 4608
(2019/09/09)
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- Practical Cleavage of Acetals by Using an Odorless Thiol Immobilized on Silica
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A practical, efficient and general method was developed for the deprotection of a variety of aromatic and aliphatic acetals to their corresponding catechol or diol derivatives using thiol immobilized on silica gel. This is an application for the well-known commercial solid-supported thiol (SiliaMetS Thiol). The procedure is mild and amenable to scale-up. It does not require inert atmosphere and clean conversions were observed. This method is applicable to substituted 1,3-benzodioxole and aliphatic acetals with different functionalities. It offers the advantage of a general route with high yield, which can be undertaken at ambient temperature.
- de Léséleuc, Mylène,Kukor, Andrew,Abbott, Shaun D.,Zacharie, Boulos
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p. 7389 - 7393
(2019/12/03)
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- An Efficient Aerobic Oxidation Protocol of Aldehydes to Carboxylic Acids in Water Catalyzed by an Inorganic-Ligand-Supported Copper Catalyst
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A method for the aerobic oxidation of aldehydes to carboxylic acids in water by using an inorganic-ligand-supported copper catalyst was developed. This method was performed with the use of atmospheric oxygen as the sole oxidant under extremely mild aqueous conditions, and furthermore, a wide range of aldehydes with various functional groups were tolerated. The copper catalyst could be recycled and used in successive reactions at least six times without any appreciable degradation in performance. This method is operationally simple and avoids the use of high-costing, toxic, air/moisture-sensitive, and commercially unavailable organic ligands. The generality of this method gives it potential to be used on the industrial scale.
- Yu, Han,Ru, Shi,Zhai, Yongyan,Dai, Guoyong,Han, Sheng,Wei, Yongge
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p. 1253 - 1257
(2018/02/16)
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- Levulinic acid upgrade to succinic acid with hydrogen peroxide
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Levulinic acid is produced from the acidic aqueous degradation of 5-hydroxymethylfurfural, with potential applications in bio-value added chemicals synthesis. Here, we report for the first time, the Baeyer-Villiger oxidation of levulinic acid to succinic acid, with hydrogen peroxide and tungstic acid at mild conditions and without any organic solvent. We investigated the effects of time, amount of reagent-to-catalyst molar ratio and H2O2-to-levulinic acid molar ratio. The maximum succinic acid selectivity was 75% with a levulinic acid conversion as high as 48%, after 6 h at 90 °C. We propose a reaction mechanism based on results obtained from the reactivity of the intermediates. The catalyst interacts with the substrate, forming a cyclic species that enhances the formation of succinic acid versus 3-hydroxypropanoic acid.
- Carnevali, Davide,Rigamonti, Marco G.,Tabanelli, Tommaso,Patience, Gregory S.,Cavani, Fabrizio
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- Revisiting alkaline aerobic lignin oxidation
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Lignin conversion to renewable chemicals is a promising means to improve the economic viability of lignocellulosic biorefineries. Alkaline aerobic oxidation of lignin has long been employed for production of aromatic compounds such as vanillin and syringaldehyde, but this approach primarily focuses on condensed substrates such as Kraft lignin and lignosulfonates. Conversely, emerging lignocellulosic biorefinery schemes enable the production of more native-like, reactive lignin. Here, we revisit alkaline aerobic oxidation of highly reactive lignin substrates to understand the impact of reaction conditions and catalyst choice on product yield and distribution. The oxidation of native poplar lignin was studied as a function of temperature, NaOH loading, reaction time, and oxygen partial pressure. Besides vanillin and syringaldehyde, other oxidation products include acetosyringone and vanillic, syringic, and p-hydroxybenzoic acids. Reactions with vanillin and syringaldehyde indicated that these compounds are further oxidized to non-aromatic carboxylic acids during alkaline aerobic oxidation, with syringaldehyde being substantially more reactive than vanillin. The production of phenolic compounds from lignin is favored by high NaOH loadings and temperatures, but short reaction times, as the products degrade rapidly, which is further exacerbated by the presence of oxygen. Under optimal conditions, a phenolic monomer yield of 30 wt% was obtained from poplar lignin. Testing a range of catalysts showed that Cu-containing catalysts, such as CuSO4 and LaMn0.8Cu0.2O3, accelerate product formation; specifically, the catalyst does not increase the maximum yield, but expands the operating window in which high product yields are obtainable. We also demonstrate that other native and isolated lignin substrates that are significantly chemically modified are effectively converted to phenolic compounds. Finally, alkaline aerobic oxidation of native lignins was compared to nitrobenzene oxidation and reductive catalytic fractionation, as these methods constitute suitable benchmarks for lignin depolymerization. While nitrobenzene oxidation achieved a somewhat higher yield, similar monomer yields were obtained through RCF and alkaline aerobic oxidation, especially for lignins with a high guaiacyl- and/or p-hydroxyphenyl-content, as syringyl units are more unstable during oxidation. Overall, this study highlights the potential for aerobic lignin oxidation revisited on native-like lignin substrates.
- Schutyser, Wouter,Kruger, Jacob S.,Robinson, Allison M.,Katahira, Rui,Brandner, David G.,Cleveland, Nicholas S.,Mittal, Ashutosh,Peterson, Darren J.,Meilan, Richard,Román-Leshkov, Yuriy,Beckham, Gregg T.
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p. 3828 - 3844
(2018/08/21)
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- Rearrangements and Tautomeric Transformations of Heterocyclic Compounds in Homogeneous Reaction Systems Furfural–Н2О2–Solvent
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General information on the reactions of furfurals with hydrogen peroxide is given. We have discussed the Baeyer–Villiger rearrangement of furan 2-hydroxyhydroperoxides and tautomeric transformations with proton transfer of 2-hydroxyfuran and β-formylacrylic acid formed in a homogeneous reaction system furfural–Н2О2–solvent under the catalysis with the formed acids. The factors affecting these rearrangements and tautomeric transformations as well as their specificity in comparison with benzene type compounds, and the pathway of the reactions of furan aldehydes with Н2О2 in water have been analyzed. Ketoenol tautomerism of cyclic hemiacetal form of β-formylacrylic acid leading to its transformation into succinic anhydride has been described for the first time.
- Badovskaya,Poskonin
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p. 1568 - 1579
(2018/11/10)
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- Electronic grade malonic acid
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Disclosed is electronic grade malonic acid. The electronic grade malonic acid is obtained by hydrolyzing of dimethyl malonate and deionized water in the existence of a catalyst. The content of the dimethyl malonate and the deionized water is larger than 99.8%, the moisture content is smaller than 50PPM, the chloride content is smaller than 5PPM, the sulfate content is smaller than 5PPM, and the content of heavy metal ions is smaller than 5PPM. The technical problems that the yield of malonic acid in the prior art is low; and the quality on the aspects of purity, impurities, chloride, sulfate and heavy metal cannot meet the using requirement of the electronic industry are effectively solved.
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-
Paragraph 0012; 0015
(2017/08/18)
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- Method for preparing aliphatic dicarboxylic acid
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The invention discloses a method for preparing aliphatic dicarboxylic acid. High-purity aliphatic dicarboxylic acid is prepared from an aliphatic diketone compound in the presence condition of halogen elements by a non-oxidation process. According to the method, an expensive transition metal-metal oxide catalytic system is not needed, the reaction condition is mild, few byproducts are produced, the purity of the products is high, and the method is suitable for large-scale industrialized production.
- -
-
Paragraph 0047; 0048
(2017/09/05)
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- An Efficient Iron(III)-Catalyzed Aerobic Oxidation of Aldehydes in Water for the Green Preparation of Carboxylic Acids
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The first example of a heterogeneous iron(III)-catalyzed aerobic oxidation of aldehydes in water was developed. This method utilizes 1 atmosphere of oxygen as the sole oxidant, proceeds under extremely mild aqueous conditions, and covers a wide range of various functionalized aldehydes. Chromatography is generally not necessary for product purification. Its operational simplicity, gram-scale oxidation, and the ability to successively reuse the catalyst, make this new methodology environmentally benign and cost effective. The generality of this methodology gives it the potential to be used on an industrial scale.
- Yu, Han,Ru, Shi,Dai, Guoyong,Zhai, Yongyan,Lin, Hualin,Han, Sheng,Wei, Yongge
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p. 3867 - 3871
(2017/03/27)
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- Degradation of the Cellulosic Key Chromophore 5,8-Dihydroxy-[1,4]-naphthoquinone by Hydrogen Peroxide under Alkaline Conditions
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5,8-Dihydroxy-[1,4]-naphthoquinone (DHNQ) is one of the key chromophores in cellulosic materials. Its almost ubiquitous presence in cellulosic materials makes it a target molecule of the pulp and paper industry's bleaching efforts. In the presented study, DHNQ was treated with hydrogen peroxide under alkaline conditions at pH 10, resembling the conditions of industrial hydrogen peroxide bleaching (P stage). The reaction mechanism, reaction intermediates, and final degradation products were analyzed by UV/vis, NMR, GC-MS, and EPR. The degradation reaction yielded C1-C4 carboxylic acids as the final products. Highly relevant for pulp bleaching are the findings on intermediates of the reaction, as two of them, 2,5-dihydroxy-[1,4]-benzoquinone (DHBQ) and 1,4,5,8-naphthalenetetrone, are potent chromophores themselves. While DHBQ is one of the three key cellulosic chromophores and its degradation by H2O2 is well-established, the second intermediate, 1,4,5,8-naphthalenetetrone, is reported for the first time in the context of cellulose discoloration.
- Zwirchmayr, Nele Sophie,Hosoya, Takashi,Henniges, Ute,Gille, Lars,Bacher, Markus,Furtmüller, Paul,Rosenau, Thomas
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p. 11558 - 11565
(2017/11/10)
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- Catalytic hydrolysis of hydrophobic esters on/in water by high-silica large pore zeolites
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Hydrolysis of water-insoluble esters is an industrially important but challenging reaction, because the esters are mostly present in oil droplets on water during the reaction. On the basis of the screening results for hydrolysis of a water-insoluble ester, 3-phenylpropionate, on/in water by 25 types of heterogeneous and homogenous catalysts, we have found that Hβ zeolite with a moderate Si/Al ratio (Si/Al = 75), Hβ-75, is an effective and reusable catalyst for hydrolysis of hydrophobic esters. The hydrolysis of esters with different sizes is studied by Hβ and HZSM5 zeolites with different Si/Al ratios, and the results show the hydrophobicity, pore size and number of Br?nsted acid sites are critical factors affecting the catalytic activity for this system. Kinetic and adsorption studies show that the high yields by Hβ-75 are due to preferential interaction of the hydrophobic zeolite pore with hydrophobic esters over polar molecules (carboxylic acids, water, alcohols) and transfer of the carboxylic acids to the oil droplets on water, both of which inhibit the reverse reaction (esterification of the carboxylic acids).
- Siddiki,Toyao, Takashi,Kon, Kenichi,Touchy, Abeda S.,Shimizu, Ken-ichi
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p. 741 - 748
(2016/12/09)
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- Role of Nitrogen Doping on the Performance of Carbon Nanotube Catalysts: A Catalytic Wet Peroxide Oxidation Application
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Four magnetic carbon nanotube (CNT) samples (undoped, completely N-doped, and two selectively N-doped) were synthesized by chemical vapor deposition. The materials were tested in the catalytic wet peroxide oxidation (CWPO) of highly concentrated 4-nitrophenol solutions (4-NP, 5 g L?1). Relatively mild operating conditions were considered (atmospheric pressure, T=50 °C, pH 3), using a catalyst load of 2.5 g L?1 and the stoichiometric amount of H2O2 needed for the complete mineralization of 4-NP. N-doping was identified to influence considerably the CWPO performance of the materials. In particular, undoped CNTs, with a moderate hydrophobicity, favor the controllable and efficient decomposition of H2O2 into highly reactive hydroxyl radicals (HO.), thus showing high catalytic activity for 4-NP degradation. On the other hand, the completely N-doped catalyst, fully hydrophilic, favors a quick decomposition of H2O2 into nonreactive O2 and H2O species. The selectively N-doped amphiphilic catalysts, that is, hybrid structures containing undoped sections followed by N-doped ones, provided intermediate results, namely, a higher N content favored H2O2 decomposition towards nonreactive H2O and O2 species, whereas a lower N content resulted in the formation of HO., increasing 4-NP mineralization. Catalyst stability and reusability were also investigated by consecutive CWPO runs.
- Martin-Martinez, Maria,Ribeiro, Rui S.,Machado, Bruno F.,Serp, Philippe,Morales-Torres, Sergio,Silva, Adrián M. T.,Figueiredo, José L.,Faria, Joaquim L.,Gomes, Helder T.
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p. 2068 - 2078
(2016/07/07)
-
- Hydrothermal conversion of glucose into lactic acid with sodium silicate as a base catalyst
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In this paper, the hydrothermal conversion of glucose to lactic acid (LA) using sodium silicate (Na2SiO3) as a mild base catalyst was investigated. The results showed that Na2SiO3 was effective catalyst for the conversion of glucose. The highest LA yield of about 30% was obtained from glucose with a lower concentration of Na2SiO3 at 300 °C for 60 s. It was also found that the use of Na2SiO3 led to a much less corrosion and a higher LA yield than that with NaOH at the same pH value. This process provides an environmentally friendly and highly effective method toward the synthesis of useful LA from glucose.
- Duo, Jia,Zhang, Zhengshuai,Yao, Guodong,Huo, Zhibao,Jin, Fangming
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p. 112 - 116
(2016/02/03)
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- POLYESTER MODIFIER COMPOSITION FOR CELLULOSE ESTER RESIN, CELLULOSE ESTER OPTICAL FILM, AND POLARIZING PLATE PROTECTIVE FILM
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There is provided a polyester modifier composition for a cellulose ester resin, including: a polyester resin produced by a reaction between a diol and 1,2-dicarboxycyclohexane. The modifier composition has a number-average molecular weight (Mn) in the range of 350 to 2,000 as measured by gel permeation chromatography (GPC). The polyester resin has a molecular weight of less than 350 constitutes 5% or less by mass of the modifier composition.
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-
-
- Ionic liquids breakdown by Fenton oxidation
-
Fenton oxidation has proved to be an efficient treatment for the degradation of ionic liquids (ILs) of different families viz. imidazolium, pyridinium, ammonium and phosphonium, in water. The intensification of the process, defined as the improvement on the efficiency of H2O2 consumption, by increasing the temperature is necessary to avoid high reaction times and the need of large excess of H2O2. In this work, temperatures within the range of 70-90°C have been used, which allowed an effective breakdown of the ILs tested (1 g L-1 initial concentration) with the stoichiometric amount of H2O2 and a relatively low Fe3+dose (50 mg L-1). Under these conditions conversion of the ILs was achieved in less than 10 min, with TOC reductions higher than 60% upon 4 h reaction time, except for the phosphonium IL. The remaining TOC corresponded mainly to short-chain organic acids. The treatment reduced substantially the ecotoxicity up to final values below 0.01 TU in most cases and a significant improvement of the biodegradability was achieved. Upon Fenton oxidation of the four ILs tested hydroxylated compounds of higher molecular weight than the starting ILs, fragments of ILs partially oxidized and short-chain organic acids were identified as reaction by-products. Reaction pathways are proposed.
- Munoz, Macarena,Domínguez, Carmen M.,De Pedro, Zahara M.,Quintanilla, Asunción,Casas, Jose A.,Rodriguez, Juan J.
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-
- Production of nanocatalyst from natural magnetite by glow discharge plasma for enhanced catalytic ozonation of an oxazine dye in aqueous solution
-
Cheap natural magnetite (NM) was modified with oxygen plasma owing to its cleaning effect by chemical etching and with argon plasma due to its sputtering effect resulting in more surface roughness. These plasmas were utilized individually or in the order of first O2 and then Ar plasmas, respectively. The performance of the plasma treated magnetites (PTMs) was higher than NM for treatment of Basic Blue 3 (BB3) in catalytic ozonation (O3/PTM). The properties of NM and the most efficient treated magnetite (PTM4) samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) and scanning electron microscopy (SEM) methods. The optimal values were chosen for operational parameters including ozone concentration (0.3 g/L), initial pH (6.7) and PTM4 dosage (600 mg/L). GC-Mass analysis was applied to detect intermediates. Environmentally-friendly treatment of the NM, simple separation of the catalyst, negligible leached iron concentration, successive reusability at milder pH and unaffected efficiency in the presence of inorganic salts are the main advantages of the PTM4.
- Taseidifar, Mojtaba,Khataee, Alireza,Vahid, Behrouz,Khorram, Sirous,Joo, Sang Woo
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p. 218 - 226
(2015/05/20)
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- BiOBr photocatalyzed decarboxylation of glutamic acid: reaction rates, intermediates and mechanism
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The degradation of glutamic acid by BiOBr under both UV and visible irradiation was investigated and compared with degradation by TiO2/UV. Analysis of the reaction rates and the distribution of intermediates was used to show that both BiOBr systems, unlike the TiO2 system, catalyze direct substrate oxidation by valance band holes.
- Fang, Yanfen,Yang, Hongwei,Zhou, Wei,Li, Yue,Johnson, David M.,Huang, Yingping
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p. 55727 - 55730
(2015/07/15)
-
- Acylated cyanidin glycosides from the pale-violet flowers of Ionopsidium acaule (Desf.) Rchb. (Brassicaceae)
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Three new acylated cyanidin 3-sambubioside-5-glucosides (1-3) and one new acylated cyanidin 3-(3X-glucosylsambubioside)-5-glucoside (4) were isolated from the pale-violet flowers of Ionopsidium acaule (Desf.) Rchb., together with one known anth
- Tatsuzawa, Fumi,Takahashi, Narumi,Kato, Kazuhisa,Shinoda, Koichi,Saito, Norio,Honda, Toshio
-
-
- An unexpected fluctuating reactivity for odd and even carbon numbers in the TiO2-based photocatalytic decarboxylation of C2-C6 dicarboxylic acids
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The degradation behaviours of five straight-chain dicarboxylic acids (from ethanedioic acid to hexanedioic acid) were compared in aqueous TiO 2-based photocatalysis. When all other conditions were identical, the degradation rates were found to fluctuate regularly with the parity of the number of carbon atoms. Dicarboxylic acids with an even number of carbon atoms (e-DAs) always degraded more slowly than those acids with an odd number of carbon atoms (o-DAs). This unusual fluctuation in the reactivity for the degradation of dicarboxylic acids by TiO2-based photocatalysis is very closely related to the different pre-coordination modes of the acids with the photocatalyst. Attenuated total reflection FTIR (ATR-FTIR) of e-DAs labelled with 13C showed that both carboxyl groups of the acid coordinate to TiO2 through bidentate chelating forms. In contrast, only one carboxyl group of the o-DAs coordinated to TiO2 in a bidentate chelating manner, whereas the other formed a monodentate binding linkage. The bidentate chelating form with bilateral symmetric coordination did not favour degradation. Isotope-labelling experiments were performed with 18O2 to observe the different ways in which incorporated oxygen entered the initial decarboxylated products of e- and o-DAs. For the degradation of butanedioic acid, (45.9±0.5) % of the oxygen in the formed propanedioic acid came from H2O, whereas for pentanedioic acid, (97.4±0.2) % of the oxygen in the formed butanedioic acid came from H2O. Our results demonstrate that in TiO2-based photocatalysis, the reactivity of active species, such as .OH/h vb+, is far from non-selective and that the attacks of these active species on organic substrates are significantly affected by the coordination patterns of the substrates on the TiO2 surface.
- Sun, Yiran,Chang, Wei,Ji, Hongwei,Chen, Chuncheng,Ma, Wanhong,Zhao, Jincai
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p. 1861 - 1870
(2014/03/21)
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- Synthesis of Pd nanoparticles decorated with graphene and their application in electrocatalytic degradation of 4-chlorophenol
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Pd/graphene catalysts were prepared in situ from graphite oxide and palladium salts by the hydrogen-reduction method and were then used for the construction of Pd/graphene gas-diffusion electrodes (GDE). The prepared catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential pulse voltammetry (DPV) techniques. In the Pd/graphene catalysts, Pd particles, with an average size of 3.6 nm and an amorphous structure, were highly dispersed in the graphene. The Pd/graphene catalysts accelerated the two-electron reduction of O2to H2O2by feeding air, which favors the production of hydroxyl radicals (HO?). In the electrolytic system, HO? was determined in the reaction mixture by the electron spin resonance spectrum (ESR). The dechlorination degree of 4-chlorophenol reached approximately 90.5% after 80 min, and the removal efficiency and the average removal efficiency of 4-chlorophenol. in terms of total organic carbon (TOC) after 120 min, reached approximately 93.3% and 85.1%, respectively. Furthermore, based on the analysis of electrolysis intermediates by high performance liquid chromatography (HPLC) and ion chromatography (IC), a reaction scheme was proposed for the Pd/grapheme GDE catalytic degradation of 4-chlorophenol.
- Bian, Zhao-Yong,Bian, Yu,Wang, Hui,Ding, Ai-Zhong
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p. 7279 - 7285
(2015/01/09)
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- Influence of silver on the glycerol electro-oxidation over AuAg/C catalysts in alkaline medium: A cyclic voltammetry and in situ FTIR spectroscopy study
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In the present work, we investigated the influence of silver on the glycerol electro-oxidation over carbon-supported AuAg catalysts by cyclic voltammetry and in situ FTIR spectroscopy. We observed that the presence of Ag in the bimetallic materials provided a more efficient catalyst in terms of the ability to electro-oxidize glycerol at relatively low potentials. On the other hand, the bimetallic catalysts were found to be less promising than the Au/C catalyst with respect to the reaction rate. Ag addition influenced the mechanism of glycerol electro-oxidation, favoring the C-C-C bond breaking, as evidenced by the selective formation of formic acid on the bimetallic catalysts. The impact of Ag on the glycerol electro-oxidation over AuAg/C may be driven by electronic modifications and Ag segregation on the catalysts surface.
- Gomes,Garcia,Gasparotto,De Souza,Ferreira,Pires,Tremiliosi-Filho
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p. 361 - 368
(2014/12/10)
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- Monoterpene glycosides, phenylpropanoids, and acacetin glycosides from Dracocephalum foetidum
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Chemical investigation of the acetone extract from the aerial parts of the Mongolian medicinal plant Dracocephalum foetidum resulted in the isolation of three limonene glycosides, a caffeic acid trimer, four rosmarinic acid glucosides, and five acacetin acyl glycosides, together with 13 known natural products. The chemical structures of all of the compounds were determined by spectroscopic analyses. Among these compounds three showed hyaluronidase inhibitory activity. In addition, one other compound showed stronger 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity than the positive control Trolox, whereas three other compounds demonstrated a similar activity to that of Trolox.
- Selenge, Erdenechimeg,Murata, Toshihiro,Tanaka, Shiho,Sasaki, Kenroh,Batkhuu, Javzan,Yoshizaki, Fumihiko
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-
- Degradation of 2,5-dihydroxy-1,4-benzoquinone by hydrogen peroxide: A combined kinetic and theoretical study
-
2,5-Dihydroxy-1,4-benzoquinone (DHBQ) is one of the key chromophores formed upon aging in cellulosic materials. This study addresses the degradation mechanism of DHBQ by hydrogen peroxide to provide a solid knowledge base for optimization of bleaching sequences aiming at DHBQ removal. Kinetic analysis provided an activation energy (Ea) of 20.4 kcal/mol. Product analyses indicated the product mixture to contain malonic acid, acetic acid, and carbon dioxide. DFT(B3LYP) computation presented a plausible mechanism for the formation of these products from DHBQ. DHBQ forms intermediate I2k, having an intramolecular O-O bridge between C-2 and C-5 of the 1,4-cyclohexadione structure. This O-O bond is homolytically cleaved, and the subsequent β-fragmentation of the resulting radical forms ketene and oxaloacetic acid. While ketene yields acetic acid, oxaloacetic acid then gives malonic acid and carbon dioxide through further attack of hydrogen peroxide via an intermediate that is oxidatively decarboxylated. The calculated Ea value (23.3 kcal/mol) in the rate-determining step, i.e., the homolysis of I2k, agreed well with the experimental value. There is also a minor pathway in which the spin state changes to triplet during the homolysis of I2k; in this way two malonyl radicals are formed that are converted to two molecules of malonic acid.
- Hosoya, Takashi,Rosenau, Thomas
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supporting information
p. 3176 - 3182
(2013/07/04)
-
- Response surface methodology for oxidative degradation of the basic yellow 28 dye by temperature and ferrous ion activated persulfate
-
The decomposition of the persulfate by Fe2+ ions results in the production of oxidative sulfate radical anions. In present study, the oxidative degradation of the basic yellow 28 dye solution was studied by using persulfate and ferrous ions. To
- G?zmen, Belgin,S?nmez, ?zgür,Turabik, Meral
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p. 6831 - 6839
(2013/07/26)
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- New environmentally friendly oxidative scission of oleic acid into azelaic acid and pelargonic acid
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Oleic acid (OA) is a renewable monounsaturated fatty acid obtained from high oleic sunflower oil. This work was focused on the oxidative scission of OA, which yields a mono-acid (pelargonic acid, PA) and a di-acid (azelaic acid, AA) through an emulsifying system. The conventional method for producing AA and PA consists of the ozonolysis of oleic acid, a process which presents numerous drawbacks. Therefore, we proposed to study a new alternative process using a green oxidant and a solvent-free system. OA was oxidized in a batch reactor with a biphasic organic-aqueous system consisting of hydrogen peroxide (H 2O2, 30 %) as an oxidant and a peroxo-tungsten complex Q3{PO4[WO(O2)2]4} as a phase-transfer catalyst/co-oxidant. Several phase-transfer catalysts were prepared in situ from tungstophosphoric acid, H2O2 and different quaternary ammonium salts (Q+, Cl-). The catalyst [C5H5N(n-C16H33)] 3{PO4[WO(O2)2]4} was found to give the best results and was chosen for the optimization of the other parameters of the process. This optimization led to a complete conversion of OA into AA and PA with high yields (>80 %) using the system OA/H 2O2/[C5H5N(n-C16H 33)]3{PO4[WO(O2)2] 4} (1/5/0.02 molar ratio) at 85 C for 5 h. In addition, a new treatment was developed in order to recover the catalyst.
- Godard, Anais,De Caro, Pascale,Thiebaud-Roux, Sophie,Vedrenne, Emeline,Mouloungui, Zephirin
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p. 133 - 140
(2013/03/13)
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- Meteorites as catalysts for prebiotic chemistry
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From outer space: Twelve meteorite specimens, representative of their major classes, catalyse the synthesis of nucleobases, carboxylic acids, aminoacids and low-molecular-weight compounds from formamide (see figure). Different chemical pathways are identified, the yields are high for a prebiotic process and the products come in rich and composite panels.
- Saladino, Raffaele,Botta, Giorgia,Delfino, Michela,Di Mauro, Ernesto
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p. 16916 - 16922
(2014/01/06)
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- Perspectives on the kinetics of diol oxidation over supported platinum catalysts in aqueous solution
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The catalytic oxidation of a variety of terminal alcohols was performed over Pt/C with 10 bar dioxygen at 343 K in aqueous solvent at low pH. The influences of Pt particle size, carbon support, alcohol structure, and start-up conditions were explored. Although the turnover frequency was not affected by particle size or the carbon support, the structure of the alcohols affected their initial rate of conversion. Both the rate of oxidation of α,ω-diols and selectivity of the diols to the diacids increased with increasing carbon chain length. The rate of 1,6-hexanediol oxidation was independent of dioxygen pressure and the order of reaction with respect to diol concentration depended on the start-up conditions. A kinetic model involving two types of metal sites was proposed to account for the experimental observations.
- Ide, Matthew S.,Davis, Robert J.
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-
- A tetra-acylated cyanidin 3-sophoroside-5-glucoside from the purple-violet flowers of Moricandia arvensis (L.) DC. (Brassicaceae)
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A novel tetra-acylated cyanidin 3-sophoroside-5-glucoside was isolated from the purple-violet flowers of Moricandia arvensis (L.) DC. (Family: Brassicaceae), and determined to be cyanidin 3-O-[2-O-(2-O-(4-O-(6-O-(4-O- (β-glucopyranosyl)-trans-caffeoyl)-β-glucopyranosyl)-trans-caffeoyl) -β-glucopyranosyl)-6-O-(trans-caffeoyl)-β-glucopyranoside] -5-O-[6-O-(malonyl)-β-glucopyranoside] by chemical and spectroscopic methods.
- Tatsuzawa, Fumi,Ito, Shun,Sato, Motoki,Muraoka, Hiroki,Kato, Kazuhisa,Takahata, Yoshihito,Ogawa, Satoshi
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p. 170 - 173
(2013/08/25)
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- Triacylated peonidin 3-sophoroside-5-glucosides from the purple flowers of Moricandia ramburii Webb.
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Triacylated peonidin 3-sophoroside-5-glucosides were isolated from the purple flowers of Moricandia ramburii Webb. (Family: Brassicaceae), and determined to be peonidin 3-O-[2-O-(2-O-(trans-feruloyl)-glucosyl)-6-O-(trans-p- coumaroyl)-glucoside]-5-O-[6-O-(malonyl)-glucoside] (1), peonidin 3-O-[2-O-(2-O-(trans-feruloyl)-glucosyl)-6-O-(cis-p-coumaroyl)-glucoside] -5-O-[6-O-(malonyl)-glucoside] (2) and peonidin 3-O-[2-O-(2-O-(trans-sinapoyl)- glucosyl)-6-O-(trans-p-coumaroyl)-glucoside]-5-O-[6-O-(malonyl)-glucoside] (3), respectively, by chemical and spectroscopic methods. In addition, one known acylated cyanidin glycoside, cyanidin 3-O-[2-O-(2-O-(trans-feruloyl)-glucosyl)- 6-O-(trans-p-coumaroyl)-glucoside]-5-O-[6-O-(malonyl)-glucoside] (4), was also identified in the flowers. Peonidin glycosides have not been reported hitherto in floral tissues in to Brassicaceae.
- Tatsuzawa, Fumi,Ito, Kanako,Muraoka, Hiroki,Namauo, Toshiharu,Kato, Kazuhisa,Takahata, Yoshihito,Ogawa, Satoshi
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experimental part
p. 73 - 77
(2012/06/30)
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- Expanding the utility of Bronsted base catalysis: Biomimetic enantioselective decarboxylative reactions
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As a result of the low reactivity of simple esters, the use of them as nucleophiles in direct asymmetric transformations is a long-standing challenge in synthetic organic chemistry. Nature approaches this difficulty through a decarboxylative mechanism, which is used for polyketide synthesis. Inspired by nature, we report guanidine-catalyzed biomimetic decarboxylative C-C and C-N bond-formation reactions. These highly enantioselective decarboxylative Mannich and amination reactions utilized malonic acid half thioesters as simple ester surrogates. It is proposed that nucleophilic addition precedes decarboxylation in the mechanism, which has been investigated in detail through the identification of intermediates by using electrospray ionization (ESI) mass-spectrometric analysis and DFT calculations. Copyright
- Pan, Yuanhang,Kee, Choon Wee,Jiang, Zhiyong,Ma, Ting,Zhao, Yujun,Yang, Yuanyong,Xue, Hansong,Tan, Choon-Hong
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supporting information; experimental part
p. 8363 - 8370
(2011/09/13)
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- Synthesis of polymer-supported copper complexes and their evaluation in catalytic phenol oxidation
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Polymer-supported metal complexes have been used as catalysts for the catalytic wet hydrogen peroxide oxidation (CWPO) of phenol. The synthesis of six catalysts derived from three polymer-supports (a polybenzimidazole resin and two poly(styrene-divinylbenzene) resins) and two Cu(II) salts. The catalytic oxidation of phenol with initial phenol concentration of 1 g L-1 was performed in a 200 mL batch stirred tank reactor at 30 °C and atmospheric pressure. Under these conditions, phenol conversion and total organic carbon conversion were evaluated. The highest phenol conversion was 93% obtained for poly(DVB-co-VBC) functionalised with iminodiacetic acid (IMDA) and loaded with copper acetylacetonate, however metal leaching was very unsatisfactory. If metal leaching was taken into consideration, it was found that polybenzimidazole loaded with copper sulphate appeared to be the most stable yielding 54% of mineralisation and 0.75 TOC/phenol conversion efficiency with simultaneously low release of metal during the oxidation.
- Castro, Isabel U.,Sherrington, David C.,Fortuny, Agustí,Fabregat, Azael,Stüber, Frank,Font, Josep,Bengoa, Christophe
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experimental part
p. 66 - 70
(2011/01/04)
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- X-ray crystallographic analysis of the 6-aminohexanoate cyclic dimer hydrolase: Catalytic mechanism and evolution of an enzyme responsible for nylon-6 byproduct degradation
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We performed x-ray crystallographic analyses of the 6-aminohexanoate cyclic dimer (Acd) hydrolase (NylA) from Arthrobacter sp., an enzyme responsible for the degradation of the nylon-6 industry byproduct. The fold adopted by the 472-amino acid polypeptide generated a compact mixed α/β fold, typically found in the amidase signature superfamily; this fold was especially similar to the fold of glutamyl-tRNAGln amido-transferase subunit A (z score, 49.4) and malonamidase E2 (z score, 44.8). Irrespective of the high degree of structural similarity to the typical amidase signature superfamily enzymes, the specific activity of NylA for glutamine, malonamide, and indoleacetamide was found to be lower than 0.5% of that for Acd. However, NylA possessed carboxylesterase activity nearly equivalent to the Acd hydrolytic activity. Structural analysis of the inactive complex between the activity-deficient S174A mutant of NylA and Acd, performed at 1.8 A resolution, suggested the following enzyme/substrate interactions: a Ser174-cis-Ser150-Lys72 triad constitutes the catalytic center; the backbone N in Ala171 and Ala172 are involved in oxyanion stabilization; Cys316-Sγ forms a hydrogen bond with nitrogen (Acd-N7) at the uncleaved amide bond in two equivalent amide bonds of Acd. A single S174A, S150A, or K72A substitution in NylA by site-directed mutagenesis decreased the Acd hydrolytic and esterolytic activities to undetectable levels, indicating that Ser174-cis-Ser150-Lys72 is essential for catalysis. In contrast, substitutions at position 316 specifically affected Acd hydrolytic activity, suggesting that Cys316 is responsible for Acd binding. On the basis of the structure and functional analysis, we discussed the catalytic mechanisms and evolution of NylA in comparison with other Ser-reactive hydrolases.
- Yasuhira, Kengo,Shibata, Naoki,Mongami, Go,Uedo, Yuki,Atsumi, Yu,Kawashima, Yasuyuki,Hibino, Atsushi,Tanaka, Yusuke,Lee, Young-Ho,Kato, Dai-Ichiro,Takeo, Masahiro,Higuchi, Yoshiki,Negoro, Seiji
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experimental part
p. 1239 - 1248
(2010/12/18)
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- Enhanced mechanism of catalytic ozonation by ultrasound with orthogonal dual frequencies for the degradation of nitrobenzene in aqueous solution
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The experiments have been performed with a semi-continuous batch reactor to investigate the degradation efficiency of nitrobenzene in aqueous solution by ultrasound with the different orthogonal dual frequencies catalytic ozonation. The introduction of ultrasound can enhance the degradation efficiency of nitrobenzene compared to the results obtained from the processes of ozonation alone and ultrasound alone. The degradation of nitrobenzene is found to be zero-order in the two systems of ultrasound alone, and the reactions follow the pseudo-first-order kinetic model in the processes of ozone alone and ozone/ultrasound. The investigation confirms that the degradation of nitrobenzene follows the mechanism of hydroxyl radical (?OH) oxidation, and the enhancement function is even more pronounced in the presence of ultrasound with the greater difference between the orthogonal dual frequencies due to the obvious synergetic effect between ozone and ultrasound, which increases the utilization efficiency of ozone, and accelerates the initiation of ?OH and the formation of H2O2, resulting in the rapid formation of an increasing diversity of byproducts and the advancement degree of mineralization of total organic carbon (TOC). The oxidative byproducts have been, respectively identified in the different processes selected, including o, p, m-nitrophenols, phenol, malonic acid, 4-nitrocatechol, nitrate ion, maleic acid, oxalic acid, hydroquinone, p-quinone, 1,2,3-trihydroxy-5-nitrobenzene and acetic acid.
- Zhao, Lei,Ma, Jun,Zhai, Xuedong
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experimental part
p. 84 - 91
(2010/11/18)
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- Oxidation-reduction of maleic acid induced by argon-hydrogen plasma-jet
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Plasma-jet in aqueous solutions is known to disproportionate water to give hydrogen and hydroxyl radicals. Maleic acid, which is a carbon-carbon double bond bearing dicarboxylic acid, underwent addition of hydrogen, hydrogen plus hydroxyl, hydroxyl species under an argon-hydrogen plasma-jet. Maleic acid (10mM) yielded 42% succinic acid (dihydrogenated product) under an argon-hydrogen (1.5 and 0.5 L min-1) plasma-jet. This demonstrates an effective reduction method for maleic acid by plasma-jet in aqueous solutions.
- Yamakawa, Isao,Ito, Yoshimi,Munegumi, Toratane,Harada, Kaoru
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scheme or table
p. 1264 - 1268
(2010/12/25)
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- Improved preparative electrochemical oxidation of d-glucose to d-glucaric acid
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The 2,2,6,6-tetramethyl-1-piperidinyloxy free radical (TEMPO) mediated electrochemical oxidation of d-glucose to d-glucaric acid on a synthetically useful scale is reported. Using TEMPO and a graphite felt anode combined with a stainless steel cathode, d-glucose was oxidized under different conditions (pH, temperature, co-oxidant), and the reaction outcomes were analyzed. Optimized conditions for such oxidation are provided along with few new interesting results unique to this reaction, such as the appearance of a novel triacid.
- Ibert, Mathias,Fuertès, Patrick,Merbouh, Nabyl,Fiol-Petit, Catherine,Feasson, Christian,Marsais, Francis
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experimental part
p. 3589 - 3594
(2010/07/08)
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