Acidic Aqueous Ethanol Research Articles

Pd-Catalyzed Oxidative Homocoupling of Arylboronic Acids in Aqueous Ethanol at Room Temperature

The authors demonstrate for the first time that the Pd(OAc)2/N,O-ligands act as catalysts toward homocoupling of arylboronic acid in aqueous ethanol (95%) under mild conditions: at room temperature and under aerobic condition. Under the optimal reaction conditions, all reactions gave the homocoupling products in good to excellent yields.

Cyclohexanone selenosemicarbazone: A convenient starting material for the preparation of functionalised selenosemicarbazones and their Pt and Pd complexes

The reaction of hydrazine hydrate with KSeCN in acidic aqueous ethanol in the presence of cyclohexanone affords cyclohexanone selenosemicarbazone in good yields. Cyclohexanone selenosemicarbazone was converted into various functionalised selenosemicarbazones by treatment with aldehydes. Salicylaldehyde selenosemicarbazone and its 1,2-naphthyl-derivative were prepared and reacted with some Pd(II) and Pt(II) phosphine complexes to give compounds of the type [M(L Se )(P)] where M = Pt and Pd, L Se is the doubly deprotonated selenosemicarbazone and P a monodentate phosphine. In these complexes the ligands act as tridentate, dianionic [Se–N–O] 2- ligands, which was confirmed by single-crystal X-ray diffraction of the Pd derivative.

Synthesis of immobilized nanopalladium on polymer-supported Schiff base, and study of its catalytic activity in the Suzuki–Miyaura reaction

Nanopalladium particles immobilized on a matrix of poly(vinyl chloride) (PVC)-supported Schiff base were prepared from PVC with sequential attachment of ethylenediamine and salicylaldehyde, followed by treatment with an ethanolic solution of palladium chloride. The as-prepared catalyst was found to be air and moisture-stable and to have significant catalytic activity in Suzuki–Miyaura reactions under mild operating conditions. Various phenyl halides were coupled with phenylboronic acid in aqueous ethanol, under air, to afford the corresponding cross-coupled products in good yields. Furthermore, the catalyst can be easily recovered by simple filtration and reused for up to five cycles without losing its activity.

Expanded Heterogeneous Suzuki–Miyaura Coupling Reactions of Aryl and Heteroaryl Chlorides under Mild Conditions

AbstractA mesoporous LTA zeolite (MP‐LTA)‐supported palladium catalyst was developed for the highly efficient Suzuki–Miyaura reaction of aryl and heteroaryl chlorides. The couplings of various aryl chlorides with arylboronic acids in aqueous ethanol were efficiently achieved in the presence of 1.0 mol% of the catalyst. Furthermore, the scope of this catalyst was extended to the coupling of heteroaryl chlorides. Regardless of the substituents, all of the coupling reactions were very clean and highly efficient under mild heating. It shows that our catalyst is one of the most powerful heterogeneous catalysts for the coupling of a wide range of aryl and heteroaryl chlorides. The catalyst could be repetitively used at least 10 times without a significant loss of its catalytic activity. Compared to mesoporous SBA‐15 and MCM‐41 materials, the MP‐LTA support proved to be very stable and robust to prevent degradation upon reuse.

One-pot synthesis of pyrano[2,3-d]pyrimidinone derivatives catalyzed by L-proline in aqueous media

An efficient protocol has been developed for the synthesis of various pyrano[2,3-d]pyrimidinones from condensation of aromatic aldehydes, malononitrile and barbituric-or thiobarbituric acid in aqueous ethanol using L-proline as a neutral bifunctional catalyst.

Chemical Oxidative Polymerization of Aminodiphenylamines

The course of oxidation of 4-aminodiphenylamine with ammonium peroxydisulfate in an acidic aqueous ethanol solution as well as the properties of the oxidation products were compared with those of 2-aminodiphenylamine. Semiconducting oligomers of 4-aminodiphenylamine and nonconducting oligomers of 2-aminodiphenylamine of weight-average molecular weights 3700 and 1900, respectively, were prepared by using an oxidant to monomer molar ratio of 1.25. When this ratio was changed from 0.5 to 2.5, the highest conductivity of oxidation products of 4-aminodiphenylamine, 2.5 x 10 (-4) S cm (-1), was reached at the molar ratio [oxidant]/[monomer] = 1.5. The mechanism of the oxidative polymerization of aminodiphenylamines has been theoretically studied by the AM1 and MNDO-PM3 semiempirical quantum chemical methods combined with the MM2 molecular mechanics force-field method and conductor-like screening model of solvation. Molecular orbital calculations revealed the prevalence of N prim-C10 coupling reaction of 4-aminodiphenylamine, while N prim-C5 is the main coupling mode between 2-aminodiphenylamine units. FTIR and Raman spectroscopic studies confirm the prevalent formation of linear N prim-C10 coupled oligomers of 4-aminodiphenylamine and suggest branching and formation of phenazine structural units in the oligomers of 2-aminodiphenylamine. The results are discussed with respect to the oxidation of aniline with ammonium peroxydisulfate, leading to polyaniline, in which 4-aminodiphenylamine is the major dimer and 2-aminodiphenylamine is the most important dimeric intermediate byproduct.

Diammonium hydrogen phosphate as a versatile and efficient catalyst for the one-pot synthesis of pyrano[2,3-d]pyrimidinone derivatives in aqueous media

Diammonium hydrogen phosphate, (NH4)2HPO4, was used as a catalyst for one-pot, three-component condensation reactions consisting of aromatic aldehydes, malononitrile and barbituric/thiobarbituric acid in aqueous ethanol at room temperature. This method has the advantages of a simple operation, mild reaction conditions, high yields, by using a less toxic and low cost chemical as a catalyst.

Heterocycles [h]Fused on 4-Oxoquinoline-3-carboxylic Acid, II. A Facile Synthesis of Some 2,7-Dioxo[1,4]thiazin[2,3-h]quinoline-8-carboxylic Acids

Model tetrahydro[1,4]thiazino[2,3-h]quinoline-8-carboxylic acids (7a-c) are synthesized via reductive lactamisation, using sodium dithionite, of the respective 7-[(carboxyalkyl)thio]-8-nitro-1,4-dihydroquinolines (5a-c). The latter compounds are made accessible via the reaction of 7-chloro-1-cyclopropyl-6-flouro-8-nitro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (4) with each of α-mercaptoacetic, α-mercaptopropionic and α-mercaptosuccinic acids in aqueous ethanol and triethylamine. The suggested structures of 5a-c and 7a-c are supported by microanalytical and spectral (IR, MS, NMR) data.

Preparation of Silica‐Coated Polystyrene Hybrid Spherical Colloids

AbstractSummary: A novel preparation method for stable PS/SiO2 core‐shell hybrid colloid was proposed. In this process, a positively charged PS colloid was first synthesized via surfactant‐free emulsion polymerization of styrene by using a cationic initiator, and the hydrolysis and condensation of tetraethoxysilane (TEOS) was then carried out in acidic aqueous ethanol medium in the presence of PS colloids. Silica layer was deposited onto the surface of PS particle via electrostatic interaction between positively charged PS colloids and negatively charged silica. No surface treatment and centrifugation/redispersion cycle process were needed. TEM, SEM, and zeta potential measurements indicated that silica layer was successfully coated onto the surfaces of PS colloids.PS/SiO2 hybrid core‐shell colloids with PS as core and silica layer as shell.imagePS/SiO2 hybrid core‐shell colloids with PS as core and silica layer as shell.

High Yields of Symmetrical Biaryls from Palladium Catalysed Homocoupling of Arylboronic Acids under Mild Conditions

Symmetrical biaryls can be obtained under very mild conditions in good yield by palladium catalysed coupling of arylboronic acids in aqueous ethanol (95%) containing sodium carbonate at ambient temperature and in the presence of oxygen.

Influence of Alkyl Substitution on the Gas-Phase Stability of 1-Adamantyl Cation and on the Solvent Effects in the Solvolysis of 1-Bromoadamantane

1-Adamantyl cations having three methyl groups or one, two, or three isopropyl groups on the 3-, 5-, and 7-positions were found by FT ICR to be more stable than the 1-adamantyl cation and that the stability increases with the number of isopropyl group. The relative stabilities calculated by PM3 were in good agreement with the experimental results. In contrast, the sequence of the rates for the solvolysis in nonaqueous solvents are 3,5,7-(Me)(3)-1-AdBr < 1-bromoadamantane (1-AdBr) < 3,5,7-(n-Pr)(3)-1-AdBr < 3,5,7-(i-Pr)(3)-1-AdBr. The rates of solvolysis of 3,5,7-(i-Pr)(3)-1-AdBr and 3,5,7-(n-Pr)(3)-1-AdBr relative to 1-AdBr at 25 degrees C are 15 and 3.8 in EtOH, respectively, but markedly decreases with the increase in the amount of added water, reaching 0.84 and 0.15, respectively, in 60% EtOH. Reflecting these effects of water, the Grunwald-Winstein (GW) relationship for 3,5,7-(i-Pr)(3)-1-AdBr and 3,5,7-(n-Pr)(3)-1-AdBr against Y(Br) is linear for nonaqueous alcohols (EtOH, MeOH, TFE-EtOH, TFE, 97% HFIP), but marked downward deviations are observed for aqueous organic solvents, in particular, aqueous ethanol and aqueous acetone. The effect of the alkyl substituents to diminish relative solvolytic reactivity in EtOH-H(2)O mixtures may be ascribed to a blend of steric hindrance to Betarphinsted base-type hydration to the beta-hydrogens and hydrophobic interaction of the alkyl groups with ethanol to make the primary solvation shell less ionizing. The introduction of one nonyl group to the 3-position showed much smaller deviations in the GW relationship than the case of 3,5,7-(n-Pr)(3)-1-AdBr. The markedly decelerated solvolysis of alkylated 1-bromoadamantanes in aqueous organic solvents is a kinetic version of anomalously diminished dissociation of alkylbenzoic acids in aqueous ethanol and aqueous tert-butyl alcohol that was demonstrated by Wepster and co-workers a decade ago and ascribed to hydrophobic effects.

Synthesis, Characterisation and Reactivity of Phenylmercury(II) Compounds Containing Hg-S Bonds

Phenylmercury(II) compounds containing Hg-S bonds of the general formulae [PhHgS[S)POGO] G = -CH2C(H)-CH3, -CH2(CH2)3CH2-and -C(CH3)2(CH3)2C- have been prepared by the reaction of PhHgOCOCH3 and the corresponding NH4 salt of O,O'-alkylene dithiophosphoric acids in aqueous ethanol. Their bimetallic derivatives with Hg(II), Cd(II) and Ag(I) salts have also been prepared. The products have been characterized using analytical and spectroscopic (IR and 1H NMR) data. Bimetallic derivatives are formed through the coordination of the sulfur atom of phenylmercury O.O'-alkylene dithiophosphate to the soft metal acceptors.

Phase behavior of α-amino acids in multicomponent aqueous alkanol solutions

A model describing the partitioning behavior of α-amino acids in systems containing water and partially miscible alkanols is presented. It incorporates a relationship expressing the solubilities of amino acids in miscible aqueous alkanol solutions and makes use of the phase behavior of the solute-free solvent system and the solubilities of amino acids in the pure solvent components. The solubilities of several amino acids in aqueous ethanol and isomeric propanol solutions and their partition coefficients in the 1-butanol + water system were taken from the literature and could succescfully be described with a single, amino acid specific, ternary interaction parameter. It is demonstrated that this parameter is related to well-established hydrophobicity scales for amino acid side-chain moieties. Without additional parameters the partition coefficients of amino acids in 1-octanol/water were predicted from the model and compare well with literature values. The extension of the model to multicomponent solvent systems is straight-forward and was demonstrated for the case of the ternary solvent system water + ethanol + 1-butanol.

Surface properties of PtCdS and mechanism of photocatalytic dehydrogenation of aqueous alcohol

Abstract The various factors influencing the photocatalytic dehydrogenation of acidic aqueous ethanol on treated PtCdS were systematically studied using X-ray photoelectron spectroscopy (XPS), spin trapping, X-ray diffraction (XRD), transmission electron microscopy (TEM), IR spectroscopy, photoacoustic spectroscopy (PAS), etc. The following conclusions can be drawn. (I) The photocatalytic dehydrogenation of aliphatic alcohols is mediated by the OH radical - the photo-oxidation product of H 2 O (2) From the energetics and reaction mechanism, a CdSCdOCd(OH) 2 layer must be formed on the surface of the PtCdS photocatalyst. (3) In acidic medium, the photoreduction product of PtCl 6 2− on CdS is PtS which can be converted to Pt 0 via high-temperature air treatment. Pt 0 traps electrons and catalyses the reduction of H + to H 2. . (4) The ·OH radical reacts quickly with the α-hydrogen atom of the alcohol producing inactive hydroxyalkyl radical, thus eliminating the corrosion of the CdS surface by ·OH. (5) Due to differences in the dipole moments, rupture energies of the α-CH bonds and steric factors of various alcohol molecules, their γ H2 values are different; the sequence is as follows: EtOH > MeOH ≈ n -PrOH ≈ n - BuOH > i-BuOH > t -BuOH ( = 0).

Studies on Viscosity and Density Behaviour of Concentrated Solutions of Chloroacetic Acids in Aqueous Ethanol

Studies on Viscosity and Density Behaviour of Concentrated Solutions of Chloroacetic Acids in Aqueous Ethanol

An Expedient Synthesis of Vicinal Diamines from Alkenes and Cycloalkenes

A new procedure for the facile preparation of various vicinal diamines is developed that utilizes diethyl N-(β-bromoalkyl)phosphoramidates 2 easily accessible by ionic addition of diethyl N,N-dibromophosphoramidate (DBPA) to alkenes and cycloalkenes 1. Crude phosphoramidates 2 are readily transformed into the corresponding ammonium ditosylates 5 by sequential azidation, Staudinger reaction with triethyl phosphite, and deprotection by refluxing with p-toluenesulfonic acid in aqueous ethanol. Diamination of cyclohexene and indene proceeds stereospecifically affording cis-1,2-diaminocyclohexane and cis-1,2-diaminoindane, respectively. Open-chain olefins do not react stereospecifically under conventional conditions yielding mixtures of diastereoisomers. Full stereochemical control of azidation can be, however, achieved when β-bromoamine hydrochlorides instead of diethyl N-(β-bromoalkyl)phosphoramidates are used as starting materials for this reaction.

Synthesis and tautomerism of ethyl 2‐(2‐benzothiazolyl)‐2‐(6‐purinyl)acetate and related compounds

AbstractReaction of 6‐chloro‐9H‐(2‐tetrahydropyranyl)purine (2d) with the sodium salt of ethyl benzothiazole‐2‐ace‐tate (1) in dimethylformamide effects condensation of the two compounds (with loss of sodium chloride) to give the corresponding ethyl diarylacetate 4 (35%), present largely as an enol chelate tautomer. Isolated as a by‐product is 6‐(2‐aminophenyl‐1‐thio)‐9H‐(2‐tetrahydropyranyl)‐purine (4%), formed via opening of the thiazole ring. Removal of the tetrahydropyranyl protective group from 4 occurs by treatment with p‐toluenesulfonic acid in aqueous ethanol to produce ethyl benzothiazole‐2‐(6‐purinyl)acetate (80%), existent largely as two enol chelate isomers. Spectral data for the various products are presented. An attempt to use 6‐chloro‐9‐acetyl‐9H‐purine in place of 2d in the first reaction gives acetylation of 1 instead of condensation.

Ultrasonic velocity and adiabatic compressibility of monochloroacetic acid in aqueous ethanol at various temperatures

Ultrasonic velocity and adiabatic compressibility of monochloroacetic acid in aqueous ethanol at various temperatures

Occurrence of a water soluble toxin in a parrotfish (Ypsiscarus ovifrons) which is probably responsible for parrotfish liver poisoning

The liver of the parrotfish Ypsiscarus ovifrons sometimes causes severe muscle pain, paralysis and dyspnea when ingested by humans. Individual livers, ovaries and digestive tracts and their contents were examined for lethal potency in mice. They were all toxic, except for livers obtained from April to June. Lethal potency ranged from 0.25 to 5.0 MU/g tissue. Livers were extracted with acidic aqueous ethanol and the extracts purified by charcoal treatment, gel filtration and partition and reversed phase column chromatography. Both the crude and partially purified toxin showed chemical and/or pharmacological properties different from those of tetrodotoxin or paralytic shellfish poisons.

ChemInform Abstract: THE MOLECULAR STRUCTURE OF 6‐(BROMOMETHYL)‐1,2,4‐TRICHLORO‐3‐ETHOXY‐3,7,7‐TRIMETHOXYBICYCLO(2.2.1)HEPTANE; AN X‐RAY STUDY

AbstractDie Addition von Ethanol an das Norbornen (I) bei der Hydrolyse von (I) in wäßrigem Ethanol erfolgt nach einem endotrans‐Mechanismus.