Kinetics and mechanism of oxidation of malonic acid by permanganate and manganese dioxide in acid perchlorate medium

Summary The kinetics of oxidation of malonic acid by both [MnO₄]^– and MnO₂ have been studied in an HClO₄ medium. The oxidation product of the organic acid was found to be glyoxylic acid. A reaction mechanism assuming complexation between MnO₂ and malonic acid is suggested. The rate is independent of [H⁺].     

The oxidation of organic substances by compounds of trivalent manganese: XIV. Oxidation of malonic acid by manganese(III) sulfate in sulfuric acid medium and with hexaquomanganese(III) ions in noncomplexing perchloric acid medium

The oxidation of malonic acid by manganese(III) sulfate in a medium of sulfuric acid and by hexaquomanganese(III) ions in a noncomplexing perchloric acid medium was studied.The reaction stoichiometry was found and the effect of the concentrations of H⁺, Mn²⁺, and HSO₄^? ions and of the initial reactant concentrations on the course and rate of the reaction was studied.The optimum conditions have been found for analytical use of the reaction, procedures have been proposed for the determination of malonic acid using the two reagents, and the accuracy and reproducibility of the determinations have been found.     

Controlled synthesis of CO2-diol from renewable starter by reducing acid value through preactivation approach

Synthesis of polyols from carbon dioxide (CO₂) is attractive from the viewpoint of sustainable development of polyurethane industry; it is also interesting to adjust the structure of the CO₂-polyols for versatile requirement of polyurethane. However, when renewable malonic acid was used as a starter, the copolymerization reaction of CO₂ and propylene oxide (PO) was uncontrollable, since it proceeded slowly (13 h) and produced 40.4 wt% of byproduct propylene carbonate (PC) with a low productivity of 0.34 kg/g. A careful analysis disclosed that the acid value of the copolymerization medium was the key factor for controlling the copolymerization reaction. Therefore, a preactivation approach was developed to dramatically reduce the acid value to ~0.6 mg(KOH)/g by homopolymerization of PO into oligo-ether-diol under the initiation of malonic acid, which ensured the controllable copolymerization, where the copolymerization time could be shortened by 77% from 13 to 3 h, the PC content was reduced by 76% from 40.4 wt% to 9.4 wt%, and the productivity increased by 61% from 0.34 to 0.55 kg/g. Moreover, by means of preactivation approach, the molecular weight as well as the carbonate unit content in the CO₂-diol was also controllable.     

Acyl Iodides in Organic Synthesis: V. Reactions with Carboxylic Acid Esters

Acyl iodides react with alkyl, alkenyl, and aralkyl esters derived from saturated, unsaturated, and aromatic mono- and dicarboxylic acids in the absence of a catalyst. The reaction involves cleavage of the OR bond and formation of organic iodide RI (including CH₂=CHI) and one or two symmetric carboxylic acid anhydrides. Phenyl acetate reacts with benzoyl iodide to give acetyl iodide and phenyl benzoate as a result of cleavage of the (O=)C–O bond. The reaction of diethyl fumarate with acetyl iodide is accompanied by cis– trans isomerization to afford maleic anhydride. In the reactions of acetyl iodide with diethyl oxalate and diethyl malonate, CO and CO₂ and CO₂ and polyketene are formed, respectively, in addition to ethyl iodide and acetic anhydride. Ethyl esters of strong organic acids, e.g., ethyl trihaloacetates, failed to react with acyl iodides under analogous conditions.     

Thermal Behaviour of Some Polyhydrocarboxylic Coordination Compounds with Neodium

New Nd-Co based polynuclear coordination compounds containing as ligand polyhydrocarboxylic acid as tartaric, malic and gluconic acids were prepared, namely: [NdCo(tart)₃]·4H₂O, (NH₄)[NdCo_0.5Cu_0.5(tart)₃]·4H₂O, (NH₄)[NdCo(malic)₃]·4H₂O, (NH₄)[NdCo_0.5Cu_0.5(malic)₃]·4H₂O, [NdCo(gluc)₄]·4H₂O and [Nd₂CoCu(gluc)₇]·5H₂O. A comparison between the thermal behaviour of the studied polynuclear coordination compounds concerning thermal stability and thermal decomposition stoichiometry was inferred. Oxalic and malonic intermediates were identified at about 300°C in the thermal decomposition of tartaric and malic compounds. In all the decomposition processes at about 400°C the presence of oxocarbonate is shown. The residual products are mixed oxides of perovskite type. This revised version was published online in August 2006 with corrections to the Cover Date.     

First heterogeneously palladium-catalysed fully selective C3-arylation of free NH-indoles

A simple heterogeneously palladium-catalysed procedure for the selective C3-arylation of indoles is reported. Under relatively standard reaction conditions (Pd-catalyst, K₂CO₃, dioxane, reflux), using only 1 mol % [Pd(NH₃)₄]/NaY as the catalyst, indoles substituted or not at position 2 gave up to 92% conversion (i.e., 85% isolated yield) towards the expected C3-arylated indole.     

Synthetic and mechanistic aspects of metal-free polymerizations of acrylates

Metal-free initiators are easily prepared from neutral CH- and NH-acidic compounds such as malonic acid esters, nitriles, sulfones, nitro-alkanes, cyclopentadiene, fluorene derivatives, carbazoles and succinimide. These anions have tetrabutylammonium ions as cationic counterions, but they are not completely free “naked” anions as traditionally assumed. Rather, anion and cation are intimately connected to each other via H-bonds. These salts initiate the polymerization of acrylates, methacrylates and acrylonitrile, forming polymers in the MW range of 1500 to 20000 with narrow molecular weight distributions (D = 1.1–1.4) in optimized cases. A completely different approach involves initiators of the type α-iodo malonic acid esters CH₃C(I)(CO₂R)₂ and α- iodo isobutyric acid esters (CH₃)₂C(I)CO₂R in combination with (nBu)₄N⁺I⁻ at 60°C. This novel initiator system is specific for metharcylates, i. e., acrylates are not polymerized.     

Production of succinic acid by anaerobiospirillum succiniciproducens

The effect of an external supply of carbon dioxide and pH on the production of succinic acid byAnaerobiospirillum succiniciproducens was studied. In a rich medium containing yeast extract and peptone, when the external carbon dioxide supply was provided by a 1.5M Na₂CO₃ solution that also was used to maintain the pH at 6.0, no additional carbon dioxide supply was needed. In fact, sparging CO₂ gas into the fermenter at 0.025 L/L-min or higher rates resulted in significant decreases in both production rate and yield of succinate. Under the same conditions, the production of the main by-product acetate was not affected by sparging CO₂ gas into the fermenter. The optimum pH (pH 6.0) for the production of succinic acid was found to be in agreement with results previously reported in the literature. Succinic acid production also was studied in an industrial-type inexpensive medium in which light steep water was the only source of organic nutrients. At pH 6.0 and with a CO₂ gas sparge rate of 0.08 L/L-min, succinate concentration reached a maximum of 32 g/L in 27 h with a yield of 0.99 g succinate/g glucose consumed.     

Kinetic Study of the Isotope Exchange Reactions of Malonic Acid and Malonate Ion Using 1H NMR Spectroscopy. Inhibition of Acid and Base

The isotope exchange reactions of malonic acid and a malonate ion were investigated in acidic and basic D₂O solutions, respectively, using ¹H NMR spectroscopy. The isotope exchange reaction of malonic acid is inhibited by the presence of DNO₃ (0–3 M) and DSO₄^? ion (0–0.1 M), whereas it is catalyzed by the presence of DSO₄^? ion (> 0.2 M), D₃PO₄, D₂PO₄^? ion or DPO₄^2– ion. The order of relative reactivity for catalyzing the isotope reaction of malonic acid in D₂O is DPO₄^2– > D₂PO₄^? > D₃PO₄ > DSO₄^? > DNO₃. The rate of the isotope exchange reaction of malonate ion in D₂O decreases to a minimum and then increases with increased [NaOD]₀. The mechanism of the isotope exchange reaction of malonic acid in acidic D₂O is different from the general acid-catalyzed mechanism generally observed for organic acids like acetic and dichloroacetic acids. The bimalonate ion plays an important role in the isotope exchange reactions of this system.     

Control of greenhouse gases emission by radiation-induced formation of useful products. Utilization of CO2

Carbon dioxide (CO₂) is produced in enormous quantities by combustion of fossil fuels in power plants and heavy industries. It is strongly influencing the environment and the climate. However, it can be separated from the exhaust gases and utilized as row material for making value-added products by irradiation. Results of experiments in laboratory scale showed, e.g. that amino acids and short chain proteins can be produced by carboxylation of amines, whereas salicylic acid results from phenol and malonic acid formation is observed from acetic acid.The yield dependence from various experimental factors as well as the reaction mechanisms of the studied systems are discussed and an outlook of future developments is given.     

One‐Step Reforming of CO2 and CH4 into High‐Value Liquid Chemicals and Fuels at Room Temperature by Plasma‐Driven Catalysis

The conversion of CO₂ with CH₄ into liquid fuels and chemicals in a single‐step catalytic process that bypasses the production of syngas remains a challenge. In this study, liquid fuels and chemicals (e.g., acetic acid, methanol, ethanol, and formaldehyde) were synthesized in a one‐step process from CO₂ and CH₄ at room temperature (30 °C) and atmospheric pressure for the first time by using a novel plasma reactor with a water electrode. The total selectivity to oxygenates was approximately 50–60 %, with acetic acid being the major component at 40.2 % selectivity, the highest value reported for acetic acid thus far. Interestingly, the direct plasma synthesis of acetic acid from CH₄ and CO₂ is an ideal reaction with 100 % atom economy, but it is almost impossible by thermal catalysis owing to the significant thermodynamic barrier. The combination of plasma and catalyst in this process shows great potential for manipulating the distribution of liquid chemical products in a given process.     

Carbon Suboxide in Preparative Organic Chemistry. New synthetic methods (1)

Although it has been known for nearly 70 years, carbon suboxide was used almost exclusively for the preparation of simple malonic acid derivatives until about 1960. Since then, however, the significance of this unusual “bisketene” has steadily increased in synthetic chemistry (especially that of heterocyclic compounds). This progress report surveys the possible applications of C₃O₂ in preparative organic chemistry, including photochemical reactions.     

Hydrolysis of new phthalimide-derived esters catalyzed by immobilized lipase

The last step of the production of four phthalimide-derived acids, designed to act as antiasthma drugs, was performed by enzymatic hydrolysis of the respective methyl or ethyl esters. The esters 4-ethyl-[2-(1,3-dioxo-1,3-dihydro-2-isoindoylyl)]-phenoxyacetic methyl ester (PHT-MET), 4-ethyl-[2-(1,3-dioxo-1,3-dihydro-2-isoindoylyl)]-phenoxyacetic ethyl ester, 4-(1,3-dioxo-1,3-dihydro-2-isoindoylyl)-phenoxyacetic ethyl ester, and 2-(1,3-dioxo-1, 3-dihydro-2-isoindoylyl)-phenoxyacetic ethyl ester were hydrolyzed by immobilized lipase. The enzymatic reaction could be used only to produce the desired 4-substituted compounds. The best result that was found to hydrolysis of PHT-MET, and, therefore, that ester was selected for optimization experiments in a three-phase system. Reactions were performed with solid biocatalyst (Lipozyme® RM IM), organic solvent phase (ethyl acetate), and aqueous phase (saturated Na₂CO₃ solution). To optimize the reaction conditions, an experimental design optimization procedure was used. The variables studied were the amount of enzyme, the temperature, and the volume of the aqueous solution. Time course experiments were then performed for different initial enzyme concentrations (0.5, 0.9, and 1.4 U_H/mL of solvent). The optimized reaction conditions found were 20 mg of Lipozyme (0.9 U_H/mL_solvent) and 5.0 mL of Na₂CO_3(sat) at 40°C for 6 h.     

Practical Organocatalytic Synthesis of Functionalized Non‐C2‐Symmetrical Atropisomeric Biaryls

An organic acid catalyzed direct arylation of aromatic C(sp²)? H bonds in phenols and naphthols for the preparation of 1,1′‐linked functionalized biaryls was developed. The products are non‐C₂‐symmetrical, atropoisomeric, and represent previously untapped chemical space. Overall this transformation is operationally simple, does not require an external oxidant, is readily scaled up (up to 98 mmol), and the structurally diverse 2,2′‐dihydroxy biaryl (i.e., BINOL‐type), as well as 2‐amino‐2′‐hydroxy products (i.e., NOBIN‐type) are formed with complete regioselectivity. Density‐functional calculations suggest that the quinone and imino‐quinone monoacetal coupling partners are exclusively arylated at their α‐position by an asynchronous [3,3]‐sigmatropic rearrangement of a mixed acetal species which is formed in situ under the reaction conditions.     

Untersuchung der Thermolysereaktion von Malonsäuremonoarylestern

Thermolysis of malonic acid monoaryl esters gives rise to the formation of a steady-state equilibrium with diaryl malonates and free malonic acid, the latter being decarboxylated to form acetic acid. The yields of diaryl malonates are lowered by a concurrent reaction, namely the decarboxylation of the monoesters, giving aryl acetates and CO₂.

---

---

Mit 2 Abbildungen

---

H. Junek, E. Ziegler, U. Herzog undH. Kroboth, Synthesis1976, 332.     

Chemical Adsorption Strategy for DMC-MeOH Mixture Separation

The effective separation of dimethyl carbonate (DMC) from its methanol mixture through simple, inexpensive and low energy-input method is a promising and challenging field in the process of organic synthesis. Herein, a reversible adsorption strategy through the assistance of superbase and CO₂ for DMC/methanol separation at ambient condition was described. The process was demonstrated effectively via the excellent CO₂ adsorption efficiency. Notably, the protocol was also suitable to other alcohol (i.e., monohydric alcohol, dihydric alcohol, trihydric alcohol) mixtures. The study provided guidance for potential separation of DMC/alcohol mixture in the scale-up production.     

Photobiocatalysis: Activating Redox Enzymes by Direct or Indirect Transfer of Photoinduced Electrons

Biocatalytic transformation has received increasing attention in the green synthesis of chemicals because of the diversity of enzymes, their high catalytic activities and specificities, and mild reaction conditions. The idea of solar energy utilization in chemical synthesis through the combination of photocatalysis and biocatalysis provides an opportunity to make the “green” process greener. Oxidoreductases catalyze redox transformation of substrates by exchanging electrons at the enzyme′s active site, often with the aid of electron mediator(s) as a counterpart. Recent progress indicates that photoinduced electron transfer using organic (or inorganic) photosensitizers can activate a wide spectrum of redox enzymes to catalyze fuel‐forming reactions (e.g., H₂ evolution, CO₂ reduction) and synthetically useful reductions (e.g., asymmetric reduction, oxygenation, hydroxylation, epoxidation, Baeyer–Villiger oxidation). This Review provides an overview of recent advances in light‐driven activation of redox enzymes through direct or indirect transfer of photoinduced electrons.     

水溶性亚胺配体/钯催化的室温 Suzuki 反应

 设计并合成了一种新型水溶性亚胺双齿配体 I, 并得到其单晶结构. 该配体具有半配位效应和绿色化学特征, 与氯化钯组成的催化体系在空气和室温条件下, 可有效催化乙醇水溶液中的溴代芳烃与芳基硼酸的 Suzuki 交叉偶联反应. 在 n(ArBr) = 0.5 mmol, n(ArB(OH)₂) = 0.75 mmol, x(PdCl₂) = 1%, x(I) = 2%, n(K₂CO₃) = 1.0 mmol, c(EtOH) = 50% 水溶液的优化条件下, 经 20 min 反应, 分离收率即可达到 99%.     

Spectrophotometric studies of reduced molybdoantimonylphosphoric acid

Spectrophotometric studies have been used to determine the optimal formation conditions and stoichiometry of the reduced molybdoantimonylphosphoric acid. It was found that a [H⁺]/[MoO^2-₄] ratio of70± 10 was optimal for formation between 0.0008 and 0.01 M molybdenum. This corresponds to solution conditions that favor the existence of the dimeric form of molybdenum. The [H⁺]/[MoO^2-₄] criteria allows simple variation of experimental conditions. The stoichiometry of the reduced heteropoly acid was surmised to be PSb₂Mo₁₀O₄₀ from spectral studies and elemental analysis.     

Dual-Role of Polyelectrolyte-Tethered Benzimidazolium Cation in Promoting CO2/Pure Water Co-Electrolysis to Ethylene

Electrochemical CO₂ reduction reaction (CO₂RR), as a promising route to realize negative carbon emissions, is known to be strongly affected by electrolyte cations (i.e., cation effect). In contrast to the widely-studied alkali cations in liquid electrolytes, the effect of organic cations grafted on alkaline polyelectrolytes (APE) remains unexplored, although APE has already become an essential component of CO₂ electrolyzers. Herein, by studying the organic cation effect on CO₂RR, we find that benzimidazolium cation (Beim⁺) significantly outperforms other commonly-used nitrogenous cations (R₄N⁺) in promoting C₂₊ (mainly C₂H₄) production over copper electrode. Cyclic voltammetry and in situ spectroscopy studies reveal that the Beim⁺ can synergistically boost the CO₂ to *CO conversion and reduce the proton supply at the electrocatalytic interface, thus facilitating the *CO dimerization toward C₂₊ formation. By utilizing the homemade APE ionomer, we further realize efficient C₂H₄ production at an industrial-scale current density of 331 mA cm⁻² from CO₂/pure water co-electrolysis, thanks to the dual-role of Beim⁺ in synergistic catalysis and ionic conduction. This study provides a new avenue to boost CO₂RR through the structural design of polyelectrolytes.