Binodal curve of two liquid phases and solid-liquid equilibrium for water + fatty acid + ethanol systems and water + fatty acid + acetone systems

To determine the liquid-liquid-solid three-phase equilibrium (LLSE), binodal data of the liquid-liquid equilibrium (LLE) and the solid-liquid equilibrium (SLE) have been measured for the ternary water + acetone or ethanol + lauric acid, myristic acid or palmitic acid systems. The binodal region for two liquid phases increases successively in the following order of the third component: lauric acid < myristic acid < palmitic acid. The binodal regions of the ternary systems with acetone as the second component are larger than those for ethanol. These binodal curves are not highly sensitive to temperature. The isothermal solubility of these fatty acids is considerably reduced when the water content in the aqueous phase increases. The solubility of fatty acids is successively reduced in the following order: lauric acid > myristic acid > palmitic acid. The solubility of fatty acids in aqueous solutions containing acetone is smaller than in those containing ethanol. Predictions of both the binodal curve for LLE and the SLE curve by the UNIFAC method and the NRTL equation do not represent the experimental data. However, data of the binodal curve and solubility are well correlated by the NRTL equation, and also the LLSE relationship could be represented.     

On the extraction of mineral acids and uranium from alcoholic and acetonic solutions with tri-N-butyl phosphate

The extraction of hydrochloric, nitric, and sulphuric acids with TBP was studied as a function of methanol, ethanol, isopropanol, and acetone concentration in the aqueous phase. Extraction increases in the order: methanol相似文献   

The acidity constants of some pyrimidine bases in various water-organic solvent media

The acid ionization constants of some pyrimidine bases of nucleic acids were determined pH-metrically at 25 degrees C and at the constant ionic strength I = 0.10 mol l(-1) (KNO3) in pure water as well as in aqueous media containing variable mole percentages (5-30%) of organic solvents. The organic solvents used were methanol, ethanol, N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), acetonitrile, acetone and dioxane. The results obtained indicated that the acidity constants are generally decreased as the content of an organic solvent in the medium is increased. It was deduced that the hydrogen bonding interactions and the solvent basicity in addition to the electrostatic effect are the major effects influencing significantly the acid ionization process of pyrimidine bases in the different water-organic solvent media. Some thermodynamic parameters (deltaH, deltaG degrees, deltaS degrees) of the ionization process over the temperature range 5-45 degrees C in pure water were also determined and discussed.     

Variations of fluorescence efficiencies of 9-(10H)-acridone and its 4-methoxy derivative with ph. excited-state proton transfer in very weak acids and

Acridone and its 4-methoxy derivative behave as very weak acids in their lowest excited singlet states. This behavior is shown to account for the pH dependences of their fluorescence spectra in alkaline solutions. 4-Methoxyacridone is also a very weak base in its lowest excited singlet state, which results in a pH dependence of its fluorescence spectrum in dilute acidic media. Acridone, although functioning as a very weak base in its lowest excited singlet state, in acidic ethanolic water, does not demonstrate excited-state proton exchange in acidic “pure” water. This suggests selective solvation by ethanol in the mixed solvent.     

有机溶剂中微量水分的测定

绕丹宁与水在有机溶剂中发生诱导荷移反应,产生吸收光谱移动且吸收峰增大。基于此,优化了实验条件,建立了一种快速、简便、灵敏的测定有机溶剂中微量水分的新方法。甲醇、醋酸溶剂中的水分含量分别在3％-10％（φ）、0～4％（φ）范围及乙醇、1-丙醇、丙酮、乙酸乙酯溶剂中水分含量在0～5％（φ）范围内与吸光度（A）呈线性关系。其相关系数分别是0．9992、0．9996、0．9992、0．9982、0．9990和0．9995。使用本方法测定了灯用酒精中水分含量,结果令人满意。     

Antioxidant, antimicrobial properties and phenolics of different solvent extracts from bark, leaves and seeds of Pongamia pinnata (L.) Pierre

This study appraises the antioxidant and antimicrobial attributes of various solvent extracts (absolute methanol, aqueous methanol, absolute ethanol, aqueous ethanol, absolute acetone, aqueous acetone, and deionized water) from bark, leaves and seeds of Pongamia pinnata (L.) Pierre. Maximum extraction yield of antioxidant components from bark (16.31%), leaves (11.42%) and seeds (21.51%) of P. pinnata was obtained using aqueous methanol (20:80). Of the extracts tested, the bark extract, obtained with aqueous methanol, exhibited greater levels of total phenolics [6.94 g GAE/100 g dry weight (DW)], total flavonoids (3.44 g CE/100 g DW), inhibition of linoleic acid peroxidation (69.23%) and DPPH radical scavenging activity (IC(50) value, 3.21 μg/mL), followed by leaves and seeds extracts. Bark extract tested against a set of bacterial and fungal strains also revealed the strongest antimicrobial activity with the largest inhibition zone and lowest minimum inhibitory concentration (MIC). HPLC analysis of aqueous methanol extracts from bark, leaves and seeds indicated the presence of protocatechuic, ellagic, ferulic, gallic, gentisic, 4-hydroxybenzoic and 4-hydroxycinnamic acids in bark (1.50-6.70 mg/100 g DW); sorbic, ferulic, gallic, salicylic and p-coumaric acids in leaves (1.18-4.71 mg/100 g DW); vanillic, gallic and tannic acids in seeds (0.52-0.65 mg/100 g DW) as the main phenolic acids. The present investigation concludes that the tested parts of P. pinnata, in particular the bark, have strong potential for the isolation of antioxidant and antimicrobial agents for functional food and pharmaceutical uses.     

An aggregation-induced emissive chromophore as a ratiometric fluorescent sensor for cyanide in aqueous media

A para-terphenyl derivative containing a lateral diphenylamino group and two terminal dicyanovinyl groups has been designed and synthesized. This compound displays aggregation-induced emission characteristics and thus shows intense intramolecular charge transfer fluorescence even in the condensed state, including in the aggregates formed in an aqueous solvent system consisting of greater than 99% water and in the solid state. The addition of cyanide to its aggregates in aqueous media induces a large blue shift in fluorescence, enabling ratiometric fluorescence sensing of cyanide anions. In addition, its prompt fluorescence responses to cyanide anions were also observed even in the solid state.     

Verteilung von Säure,Wasser, Methanol, Äthanol und Aceton Zwischen Gemischt Wässrig-Organischen Salpetersäurelösungen und Lösungen von Trilaurylammoniumnitrat in Cyclohexan

The distribution of acid, water, methanol, ethanol and acetone between mixed aqueous-organic nitric acid solutions and solutions of trilaurylammoniumnitrate in cyclohexane has been investigated. The distribution of acid rises with increasing concentrations of nitric acid, methanol, ethanol and acetone in the mixed aqueous-organic phase. The effect of the organic additives in increasing the distribution of the acid is methanol<ethanol<acetone. The concentration of nitric acid in the organic phase can be calculated by a formula similar to that describing the extraction from pure aqueous solutions. The distribution curves of water, methanol and ethanol resemble each other, all of them showing a minimum, when the distribution ration is plotted versus the nitric acid concentration in the mixed aqueous-organic phase. The acetone distribution decreases steadily with increasing nitric acid concentration. The shape of the curves is briefly discussed.      

Developments in indicators

The use of metal ion-metallochromic indicator complexes as narrow-range pH indicators is shown to be advantageous for the titration of weak acids in aqueous media. The Cu-DBAH and the Mg-Azo Violet complexes with apparent pK values of 7.7 and 11.5 have been used for the titrations of benzoic acid and of glycine and phenol, respectively, with good precision.     

Synthesis and characterization of photo‐responsive magnetic molecularly imprinted microspheres for the detection of sulfonamides in aqueous solution

A dual responsive molecularly imprinted polymer sensitive to both photonic and magnetic stimuli was successfully prepared for the detection of four sulfonamides in aqueous media. The photoresponsive magnetic molecularly imprinted polymer was prepared by surface imprinting polymerization using superparamagnetic Fe₃O₄ nanoparticles functionalized with a silica layer as a support, water‐soluble 4‐[(4‐methacryloyloxy)phenylazo]benzenesulfonic acid as the functional monomer, and sulfadiazine as the template. The magnetic molecularly imprinted polymers showed specific affinity to sulfadiazine and its structural analogs in aqueous media. Upon alternate irradiation at 365 and 440 nm, the quantitative bind and release of the four sulfonamides by magnetic molecularly imprinted polymers occurred. Furthermore, the prepared magnetic molecularly imprinted polymers were used as solid‐phase extraction material selectively extracted the four sulfonamides from water samples with good recoveries. Thus, a simple, convenient, and reliable detection method for sulfonamides in the environment based on responsive magnetic molecularly imprinted polymers was successfully established.     

Uptake of small oxygenated organic molecules onto ammonium nitrate under upper tropospheric conditions

The uptake of formic (C1), propanoic (C3), butanoic (C4), and pentanoic (C5) acids onto ammonium nitrate (AN) has been investigated as a function of temperature and relative humidity using a Knudsen cell flow reactor coupled with FTIR-reflection absorption spectroscopy (FTIR-RAS). The uptake of acetone and methanol onto AN was also briefly studied. Initial uptake coefficients (gamma) were determined over the temperature range 200-240 K. Formic, propanoic, and butanoic acids exhibited efficient but temperature-dependent uptake on AN, with larger uptake coefficients observed at lower temperatures. Pentanoic acid was not taken up by AN under any of the conditions studied. Uptake of acetone and methanol onto AN was observed, but in insignificant amounts under atmospherically relevant conditions. Infrared spectra revealed that propanoic and butanoic acids ionized on the surface, despite the fact that the AN films were effloresced. Formic acid reacted with the AN film to produce ammonium formate and ionized nitric acid. Adding small amounts of water vapor (4% RH) to the chamber resulted in dramatically increased gamma values for all of the acids. Furthermore, the IR spectra showed the formation of a liquid layer when propanoic and butanoic acids adsorbed on the surface at RH = 20% and greater. Liquid water features were not observed at a similar relative humidity in the absence of the acids. These results show that small organic acids can be efficiently scavenged by AN and lead to enhanced water uptake under upper tropospheric conditions.     

Complexation of a Macrocycle Containing Thiopyrimidine and Uracil Moieties with Dicarboxylic and Amino Acids in Various Organic and Aqueous Organic Solutions

The complexation of a macrocycle containing thiopyrimidine and uracil moieties (M) with amino acids and some dicarboxylic acids was studied by pH-metric, UV-VIS, ¹H NMR spectroscopy methods in chloroform, methanol, aqueous 1,4-dioxane, and biphasic water–chloroform media. The complexation of M with acids is too weak to solubilize them from the solid state into chloroform solutions containing M. The ¹H NMR spectra and pH-metric data of aqueous 1,4-dioxane (80 vol.%) reveal the pH-dependent 1:1 binding between M and the acids studied. The protonation of M is not a prerequisite for binding of fumaric, succinic, o-phtalic acids and the series of amino acids, whereas binding of maleic acid requires the protonation of both thiopyrimidine moieties of M. Therefore,M·(H⁺)₂ exhibits strong selectivity towards maleic acid in aqueous 1,4-dioxane and in biphasic water–chloroform media.     

Cation-exchange behaviour of several elements in hydrofluoric acid-organic solvent media

The cation-exchange characteristics of 15 elements with the strongly acidic cation-exchange resin Dowex 50 x 8 were investigated in media containing varying concentrations of organic solvents and aqueous hydrofluoric acid. The determination of the distribution coefficients was carried out in 0.15-1.2 M hydrofluoric acid solutions containing 0-90% of the organic solvents methanol, ethanol, n-propanol, isopropanol, methyl glycol, acetone, tetrahydrofuran, and acetic acid. Based on these distribution data the possibilities of separations of the various elements are indicated and discussed.     

PEC films prepared from Chitosan-Alginate coacervates

Chitosan-alginate polyelectrolyte complex (PEC) have been prepared in situ in beads and microspheres. This study examines the preparation of suitable chitosan-alginate coacervates for casting into homogeneous PEC films for potential applications in packaging, controlled release systems and wound dressings. Coacervation between chitosan and alginate was rapid, but the rate may be controlled with the addition of water miscible organic solvents. Compared with ethanol and PEG200, acetone was the more promising solvent moderator. Suspensions of fine, uniformly dispersed coacervates were produced by a dropwise addition of 0.25% w/v chitosan solution (solvent: 1: 1 v/v of 2% acetic acid and acetone) into 0.25% w/v sodium alginate solution in water under rapid agitation. The PEC films were transparent and flexible. They exhibited high permeability to water vapor, but resisted complete dissolution in 0.1 M HCI, distilled water and pH 7.4 phosphate buffer solution. Microscopic heterogeneity in the films could be reduced by immersion in aqueous media, but this was accompanied by modifications in the thickness, permeability and mechanical property of the films.     

Study of the reaction between styrene and electrogenerated superoxide ion in dimethylformamide

The oxidation of some hydroxamic acids (RCONHOH, R=CH₃, C₆H₅, C₆H₅CH₂) has been investigated on platinum electrodes in aqueous solution buffered at different pH values. The voltammetric data showed that in acid media the dissociation of the acids in the chemical reaction preceding the quasi-reversible charge transfer step, while in alkaline media a weak adsorption of the reagent is operative. The reaction mechanism proposed in alkaline medium involves the formation of transient radical-anions, evidentiated by cyclic voltammetry, which dimerize and, by intramolecular rearrangement, quantitatively give (N,O-diaceyl)hydroxylamines. In acid media a two-electron oxidation process leads to carboxylic acids as final products.     

四-β-(氨甲基)酞菁锌盐酸盐的合成及光物理光化学性质研究

四-β-(邻苯二甲酰亚胺甲基)酞菁锌(ZnPcP4)与85%水合肼反应得到四-β-(氨甲基)酞菁锌(ZnPcN4,分子式C36H28N12Zn),其盐酸盐为ZnPcN4.HCl。测试合成得到的标题化合物紫外-可见电子吸收光谱,荧光光谱和单线态氧生成速率。标题化合物在水中聚集,在90%1,2-丙二醇/水中主要以单体形式存在。目标酞菁锌配合物在90%DMF/水的中性溶液存在聚集体,在弱酸性条件下,随酸度增大,675 nm处Q带单体吸收峰升高,在DMF/water(10%,V/V)/HCl(1.2 mmol·L-1)溶液中10-5 mol·L-1的酞菁配合物基本上没有聚集;在强酸性条件下,随酸度增大,675 nm处Q带单体吸收峰下降的同时,在713 nm处酞菁单质子化吸收峰强度有所增加。ZnPcN4.HCl在DMF体系中聚集,荧光量子产率和单线态氧量子产率变小,但其在DMF/water(10%,V/V)/HCl(1.2mmol·L-1)体系中主要以单体形式存在,荧光量子产率为0.19,单线态氧量子产率0.58,光敏活性与标准无取代酞菁锌相近。     

Cyclic imides III. A study of the hydroxy- and methoxyphthalimidoacetic acids and the methyl methoxyphthalimidoacetates

The hydroxy- and methoxyphthalimidoacetic acids and the methyl methoxyphthalimidoacetates have been synthesized. The ultraviolet absorption spectra of these compounds in 95% ethanol, aqueous acid, and aqueous base are discussed. Structures are suggested for the hydroxy- and methoxyphthalamate ions which are formed in basic solution. The Gabriel-Colman rearrangements of methyl 3- and 4 - methoxyphthalimidoacetate give, respectively, 8-methoxy-4-hydroxy-3 - carbomethoxy-1(2H)-isoquinolone (VII) and 6-methoxy-4-hydroxy-3-carbomethoxy-1(2H)-isoquinolone (VIII).     

Cation-exchange behaviour of several elements in nitric acid-organic solvent media

The cation-exchange behaviour of 19 elements towards the strongly acidic cation-exchange resin Dowex 50-X8 in media containing varying concentrations of organic solvents and aqueous nitric acid is reported. Based on the determination of the distribution coefficients of these elements in the organic solvents methanol, ethanol, n-propanol, isopropanol, methyl glycol, acetone, tetrahydrofuran and acetic acid, the conditions most suitable for their quantitative separation are indicated and discussed.     

Allosteric Indicator Displacement Enzyme Assay for a Cyanogenic Glycoside

Indicator displacement assays (IDAs) represent an elegant approach in supramolecular analytical chemistry. Herein, we report a chemical biosensor for the selective detection of the cyanogenic glycoside amygdalin in aqueous solution. The hybrid sensor consists of the enzyme β‐glucosidase and a boronic acid appended viologen together with a fluorescent reporter dye. β‐Glucosidase degrades the cyanogenic glycoside amygdalin into hydrogen cyanide, glucose, and benzaldehyde. Only the released cyanide binds at the allosteric site of the receptor (boronic acid) thereby inducing changes in the affinity of a formerly bound fluorescent indicator dye at the other side of the receptor. Thus, the sensing probe performs as allosteric indicator displacement assay (AIDA) for cyanide in water. Interference studies with inorganic anions and glucose revealed that cyanide is solely responsible for the change in the fluorescent signal. DFT calculations on a model compound revealed a 1:1 binding ratio of the boronic acid and cyanide ion. The fluorescent enzyme assay for β‐glucosidase uses amygdalin as natural substrate and allows measuring Michaelis–Menten kinetics in microtiter plates. The allosteric indicator displacement assay (AIDA) probe can also be used to detect cyanide traces in commercial amygdalin samples.     

Acid-base properties of 2-phenethyldithiocarbamoylacetic acid, an antitumor agent

The acid-base properties of the 2-phenethyldithiocarbamoylacetic acid (PET) substance belonging to the class of isothiocyanates and capable of inhibiting the development of tumors on many experimental models were studied. The acidity and hydrolysis constants of the PET substance in ethanol, acetone, aqueous ethanol, and aqueous acetone solutions were determined from the data of potentiometric (pH-metric) titration of ethanol and acetone solutions of PET with aqueous solidum hydroxide at room temperature.