Heck reaction with 3-fluoro-3-buten-2-one

3-Fluoro-3-buten-2-one (2) is readily prepared from 1-fluoro-1-chloro-2-methoxy-2-methylcyclopropane (1) in 82% yield by heating the cyclopropane in aqueous quinoline solution. Ketone 2 reacts with aryl iodides (3) in a Heck reaction catalyzed by Pd(OAc)₂ to give Z-3-fluorobenzalacetones (4) in 36-86% yield.     

Formation of Hollow Solid Microparticles during Interaction of Gas with the Substance Present in Solution Microdroplets Transported by Air Flow

The hollow spherical microparticles are formed on mixing of two air flows of microdroplets of solutions of substances A and B (the substance B is readily transported from solution to gas phase) which react to yield a solid substance C, as found by scanning electron microscopy; air flows are obtained using ultrasonic generators. Outer diameter of the hollow microparticles formed is close to that of the microdroplets of the initial solution. The hollow microparticles of hydrazone are obtained by the interaction of droplets of hydrazide solution and formaldehyde entering into gas phase from microdroplets of its acidic aqueous solution. In addition, the hollow microparticles of iron hydroxycholide were obtained by the reaction of FeCl₃ aqueous solution and ammonia entering into gas phase from the microdroplets of its solution. The hollow microparticles presumably of cobalt hydroxynitrate were obtained by the reaction of microdroplets of Co(NO₃)₂ aqueous solution and ammonia. The outer diameter of the hollow particles obtained is equal to 3–10 m, and wall thickness to 2–2.5 m.     

A thermometric titration study of the interaction of Al3+, Co2+, Ni2+ and Zr4+ with xylenol orange

A thermometric titrimetry study of the interaction in aqueous solution of A1³⁺, Co²⁺, Ni²⁺ and Zr⁴⁺ with xylenol orange has revealed in each case a linear reaction heat/[Mⁿ⁺] relationship at a specified pH, thereby suggesting the potential of metallochromic indicators for the analytical determination of these metals in water. The effect of pH on the reaction heat is investigated and is interpreted in terms of the ability of these metal cations to complex with the known xylenol orange species existing at the various pH studied. An interference study, involving transition and non-transition metal ions, is also reported and the interference effect, as measured by the deviation ofQ/Q from unity (Q andQ are the relevant reaction heats in the presence and absence of interfering ion), is partially explained in terms of the coordination numbers, relative sizes and crystal field stabilization energies of the cations studied and the known behaviour of xylenol orange in aqueous solution.     

Fluorinated building blocks. The discovery of a stable difluoroallenyl indium and the synthesis of gem-difluoroallenyl and -propargyl synthons in aqueous media

The synthesis of two highly functional fluorinated motifs, TIPS-C triple bond C-CF2-, and CF2=C=C(TIPS)- is described. This approach is mediated by a room-temperature stable ethereal solution of a difluoroallene indium intermediate. This intermediate may be used as "stock solution" in the reaction with aqueous HCHO, to yield CF2=C=C(TIPS)CH2OH, and in a reaction with a Schiff base to produce the corresponding beta,beta-difluorohomopropargylamine. The synthetic potential of CF2=C=C(TIPS)CH2-OH has been demonstrated by its conversion to a difluorodihydrofuran derivative by a facile and efficient 5-endo-trig cyclization. Homopropargylic gem-difluoro alcohols are synthesized by addition of indium to a mixture of an aldehyde and TIPS-C triple bond C-CF2Br in predominantly aqueous media.     

邻甲基苯甲醛的“槽内式”间接电合成

邻甲基苯甲醛的“槽内式”间接电合成;邻甲基苯甲醛; 氧电还原; 氧还电对V5+/V4+; 邻二甲苯; 电解     

Electropolymerization of 3-methylthiophene at liquid 3-methylthiophene | aqueous solution | graphite three-phase junction

Droplets of 3-methylthiophene are mechanically attached to the surface of paraffin-impregnated graphite electrode (PIGE) and immersed into aqueous solution of LiClO₄. It is demonstrated that the oxidative electropolymerization (observed in non-aqueous solutions) can be accomplished by potential cycling between −0.3 and 1.4 V vs. saturated calomel electrode (SCE). Since the droplets do not contain a dissolved electrolyte, the electrochemical reaction starts at the very edge of the three-phase junction organic droplet | graphite | aqueous electrolyte.     

Electrochemical study on the keto-enol tautomerization of p-hydroxyphenylpyruvic acid in aqueous solution

The keto-enol tautomerization of p-hydroxyphenylpyruvic acid (pHPP) in aqueous solutions and the complexation reaction between enolic pHPP and boric acid have been studied by electrochemical techniques including linear sweep voltammetry (LSV), pulse voltammetry, and cyclic voltammetry (CV), combining with UV spectrometry. Electrochemical techniques reveal that in aqueous solution, there are two tautomers of pHPP: enolic form and ketonic form; the former exists mainly in freshly prepared pHPP solution, and the latter exists mainly in equilibrium solution. Both enolic and ketonic pHPP are electroactive. The electrochemical oxidation of enolic pHPP gives rise to two anodic waves, I(a) and II(a), while the electrochemical oxidation of ketonic pHPP only results in the observation of the second wave II(a). The oxidation process I(a) is revealed to be associated with the quasi-reversible, two-electron two-proton oxidation of "C=C"group at the side chain of enolic pHPP, and the oxidation process II(a) is proposed to result from the irreversible oxidation of phenolic hydroxyl group. It is observed that in aqueous solution, enolic pHPP can quickly complex with boric acid to yield enol-borate complex that can also oxidize at a glassy carbon electrode to yield an anodic wave.     

Effect of Organic Compounds and Salts on the Tris(2,2"-Bipyridyl)Ruthenium(II)-Photosensitized Substitution of the Sulfo Group for Halogen in Halogenated Naphthalenes in Aqueous Solutions

The effect of the addition of organic compounds and salts on the occurrence of the chain radical-ion reaction of replacement of halogen by sulfo group in halogenated hydroxynaphthalenes in a sodium sulfite aqueous solution, which was photosensitized by a tris(2,2"-bipyridyl)ruthenium(II) complex, was studied. It was shown that both organic compounds and salts in small concentrations increase the quantum yield of the substitution reaction. The kinetic scheme of the reaction is discussed.     

Novel simple methods for the synthesis of single-phase valentinite Sb2O3

Several methods with solid and dissolved reactants were investigated as possible routes for synthesis of single-phase valentinite Sb₂O₃. The methods are based on simple chemical reaction between SbCl₃ and NaOH. The method with solid state reactants was established on self-propagating room temperature reaction (SPRT), while wet syntheses were based on the same chemical reaction, and performed in either distilled water or absolute ethanol. The prepared powders were characterized by X-ray powder diffraction, scanning electron microscopy and field emission scanning electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction (SAED) and UV/vis diffuse reflectance spectroscopy. SPRT and aqueous solution syntheses resulted in single-phase valentinite Sb₂O₃, but with significantly different morphologies. In the case of SPRT method the obtained powder contains well crystallized prismatic shaped submicronic particles, with hexagonal or lozenge basis typical for valentinite crystal structure, while aqueous solution synthesis resulted in powder containing micronic agglomerates. The ethanolic solution synthesis product was Sb₂O₃ with cubic senarmontite as predominant phase and traces of orthorhombic valentinite. It was confirmed that not only the aggregate state, but also the choice of solvent has a great influence on the structural and optical characteristics of synthesized Sb₂O₃ powders.     

Heterocyclen aus α-nitroolefinen. XI . 1,2-oxazine aus α-nitroolefinen und β-dicarbonylverbindungen

Dihydro-1,2-oxazines 8 and 12-oxazines 12 are formed by the reaction of the nitronic acids of the adducts of α-nitroolefins and β-dicarbonyl compounds ( 6 ) by two ways: A ) The nitronic acids 6 are heated in a boiling solution of urea in ethanol or methanol. B ) The nitronic acids 6 are reduced with an aqueous solution of ammoniachloride and sodium sulfide. ¹H-nmr and ¹³C-nmr investigations prove the constitutions. The mechanism is discussed.     

Palladium η3-allyl complex with sorbic acid: Kinetics and mechanism of protodemetalation in aqueous solutions

The allyl complex di-μ-chloro-bis[(1,2,3-η)-1-carboxy-3-(1-hydroxyethyl)allyl]dipalladium (which is a hydroxyl-containing palladium η³-allyl complex based on sorbic acid) has been synthesized from trans,trans-2,4-hexadienic (sorbic) acid and Na₂PdCl₄ in an aqueous solution. The complex has been isolated from the reaction solution and has been characterized by IR, ¹H NMR, and ¹³C NMR spectroscopy. Its composition has been determined by elemental analysis. The protodemetalation kinetics of the complex in aqueous solutions has been studied. The rate of this reaction obeys a second-order equation, first-order with respect to each reactant. A reaction mechanism has been derived from protodemetalation kinetics and data characterizing the state of the reactants.     

Photoluminescence of 2-(2′-hydroxy-5′-methylbenzoyl)-1,5-diphenylpyrrole in aqueous and β-cyclodextrin environments: manifestation of open and closed conformers

Steady-state fluorometric studies have been performed on 2-(2′-hydroxy-5′-methylbenzoyl)-1,5-diphenylpyrrole (HMBDPP) in aqueous and aqueous β-cyclodextrin (β-CD) environments at ambient temperature. The fluorophore mostly shows a single emission in aqueous solution. Addition of β-CD to the aqueous solution of the fluorophore results in the development of another emission band at higher energy. The difference in the fluorometric behaviour is assigned to a remarkable change in the polarity of the microenvironment within the supramolecular structural environment compared to that of the bulk aqueous phase. Semi-empirical calculation (AM1-SCI) rules out the possibility of intramolecular proton transfer reaction in any of the S₀, S₁ and T₁ states of the fluorophore. It is proposed that HMBDPP exists mostly in the intermolecularly hydrogen-bonded form (open conformer) in aqueous solution while within β-CD environment, it is the intramolecularly hydrogen-bonded form (closed conformer) that predominates.     

Spectrophotometric determination of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride by flow injection analysis.

1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC.HCl) is a very useful agent to form amide bonds (peptide bonds) in an aqueous medium. A simple and fast detection system was developed using the reaction with pyridine and ethylenediamine in acidic aqueous solution and spectrophotometric flow injection analysis. The absorbances were measured at 400 nm and the reaction was accelerated at 40 degrees C. The calibration graph showed good linearity from 0 to 10% of EDC.HCl solutions: the regression equation was y=3.15x10(4)x (y, peak area; x, % concentration of EDC.HCl). The RSD was under 1.0%. Sample throughput was 15 h(-1). This method was applied to monitoring the EDC.HCl concentration that remained after the anhydration of phthalic acid in water, esterification of acetic acid in methanol or dehydration condensation of malonic acid and ethylenediamine in water.     

Oxidation reaction of [Ni(1,4,7-triazacyclononane)(2)](2+) by [Fe(o-phenanthroline)(3)](3+) in aqueous acidic solution at elevated pressures: determination of the activation and reaction volumes for the Ni(iii)/(ii) couple

The reaction volume corresponding to the self-exchange process of the [Ni(tacn)(2)](3+/2+) couple was determined in aqueous acidic solution. Theoretical equations on the basis of the Mean Spherical Approximation were proposed for the estimation of reaction volumes for M(n+/(n- 1)+) couples in solution, and the calculated reaction volumes were compared with the experimentally estimated values. The activation volume for the [Ni(tacn)(2)](3+/2+) couple was determined in the acidic condition from the cross reaction of [Ni(tacn)(2)](2+) and [Fe(o-phen)(3)](3+) at elevated pressures. The agreement of the experimentally estimated activation volume for the [Ni(tacn)(2)](3+/2+) couple, -8.2 +/- 2.4 cm(3) mol(-1), with the theoretically calculated value, -7.5 cm(3) mol(-1), within the allowed uncertainty (+/-1 cm(3) mol(-1)) indicates that the electron self-exchange reaction of this redox couple obeys the Marcusian behavior in aqueous acidic solution.     

Reaction mechanisms and structural characterization of the reactive intermediates observed after the photolysis of 3-(hydroxymethyl)benzophenone in acetonitrile, 2-propanol, and neutral and acidic aqueous solutions

Nanosecond time-resolved resonance Raman (ns-TR(3)) spectroscopy was employed to investigate the photoinduced reactions of 3-(hydroxymethyl)benzophenone (1) in acetonitrile, 2-propanol, and neutral and acidic aqueous solutions. Density functional theory calculations were utilized to help the interpretation of the experimental spectra. In acetonitrile, the neutral triplet state 1 [denoted here as (m-BPOH)(3)] was observed on the nanosecond to microsecond time scale. In 2-propanol this triplet state appeared to abstract a hydrogen atom from the solvent molecules to produce the aryphenyl ketyl radical of 1 (denoted here as ArPK of 1), and then this species underwent a cross-coupling reaction with the dimethylketyl radical (also formed from the hydrogen abstraction reaction) to form a long-lived light absorbing transient species that was tentatively identified to be mainly 2-(4-(hydroxy(3-(hydroxymethyl)phenyl)methylene)cyclohexa-2,5-dienyl)propan-2-ol. In 1:1 H(2)O:CH(3)CN aqueous solution at neutral pH, (m-BPOH)(3) reacted with water to produce the ArPK of 1 and then underwent further reaction to produce a long-lived light absorbing transient species. Three photochemical reactions appeared to take place after 266 nm photolysis of 1 in acidic aqueous solutions, a photoreduction reaction, an overall photohydration reaction, and a novel photoredox reaction. TR(3) experiments in 1:1 H(2)O:CH(3)CN aqueous solution at pH 2 detected a new triplet biradical species, which is associated with an unusual photoredox reaction. This reaction is observed to be the predominant reaction at pH 2 and seems to face competition from the overall photohydration reaction at pH 0.     

活性艳红X-3B水溶液的光化学与光催化协同脱色反应

 对影响活性艳红X－3B水溶液光化学与光催化协同脱色反应的各种条件（如溶液的pH值,紫外光照强度,空气流量,催化剂用量及溶液的初始浓度等）进行了考察．结果表明,降解率随着紫外光照强度的增强而加快,随着X－3B初始浓度的增大而减慢;催化剂最佳用量为4g／L,空气最佳流量为4．3L／h．在X－3B水溶液的光催化脱色过程中,存在有光解反应,但它远不如光催化反应重要．因此,活性艳红X－3B水溶液的降解是光化学与光催化的协同脱色反应．     

Universal Reaction Mechanism of Boronic Acids with Diols in Aqueous Solution: Kinetics and the Basic Concept of a Conditional Formation Constant

To establish a detailed reaction mechanism for the condensation between a boronic acid, RB(OH)₂, and a diol, H₂L, in aqueous solution, the acid dissociation constants (${K{{{\rm BL}\hfill \atop {\rm a}\hfill}}}$ ) of boronic acid diol esters (HBLs) were determined based on the well‐established concept of conditional formation constants of metal complexes. The pK_a values of HBLs were 2.30, 2.77, and 2.00 for the reaction systems, 2,4‐difluorophenylboronic acid and chromotropic acid, 3‐nitrophenylboronic acid and alizarin red S, and phenylboronic acid and alizarin red S, respectively. A general and precise reaction mechanism of RB(OH)₂ with H₂L in aqueous solution, which can serve as a universal reaction mechanism for RB(OH)₂ and H₂L, was proposed on the basis of (a) the relative kinetic reactivities of the RB(OH)₂ and its conjugate base, that is, the boronate ion, toward H₂L, and (b) the determined pK_a values of HBLs. The use of the conditional formation constant, K′, based on the main reaction: RB(OH)₂+H₂L ${{\mathop \leftrightarrow \limits ^{K{_{1}}}_{}}}$ RB(L)(OH)^?+H₃O⁺ instead of the binding constant has been proposed for the general reaction of uncomplexed boronic acid species (B′) with uncomplexed diol species (L′) to form boronic acid diol complex species (esters, BL′) in aqueous solution at pH 5–11: B′+L′ ${{\mathop \leftrightarrow \limits ^{K{^\prime}}_{}}}$ BL′. The proposed reaction mechanism explains perfectly the formation of boronic acid diol ester in aqueous solution.     

Formation of tricuprotetraborate 3CuO · 2B2O3 · 6H2O in aqueous solutions

The reaction of copper sulfate, boric acid, and sodium hydroxide in an aqueous solution was studied in relation to the molar ratio and concentration of components, solution pH, temperature, and reaction duration. The conditions under which tricuprotetraborate hexahydrate 3CuO · 2B₂O₃ · 6H₂O is formed were determined.     

Bismuth triflate-chiral bipyridine complexes as water-compatible chiral Lewis acids

[reaction: see text] Catalytic asymmetric hydroxymethylation of silicon enolates with an aqueous formaldehyde solution has been developed using a chiral bismuth complex. This is the first example of highly enantioselective reactions using a chiral bismuth catalyst in aqueous media. In this paper, we have added Bi(OTf)(3)-1 complex as a "water-compatible Lewis acid". Bi(OTf)3 is unstable in the presence of water but is stabilized by the basic ligand.     

Dispersity and stability of foams obtained from poly(vinyl alcohol) solution and the properties of resulting foamed cryogels

Foams have been generated from aqueous poly(vinyl alcohol) solution by two different methods: dispersion (mechanical) method, i.e., by bubbling a gas through a porous medium into the aqueous poly(vinyl alcohol) solution, and the condensation (chemical) method, i.e., by performing a gas-generating reaction directly in the polymer solution. The effect of the formation method on foam stability and dispersity has been studied. The foam produced by the condensation method of foaming the aqueous poly(vinyl alcohol) solution with nitrogen is more stable and finely dispersed and has a higher expansion ratio than that obtained by bubbling the gas through the polymer solution. Foamed cryogels have been formed by freezing-thawing the foam resulting from the chemical reaction in the polymer solution. The values of the elasticity modulus, melting temperature, and thermal conductivity of the cryogels have been determined.