Density functional theory (DFT) calculations of the infrared absorption spectra of acetaminophen complexes formed with ethanol and acetone species

We have investigated the infrared (IR) vibrational spectra of acetaminophen (N(4-hydroxyphenyl) acetamide or paracetamol) complexes formed with ethanol and acetone in relation to the nature of the specific intermolecular interactions involved in the stabilization of the complexes. The structures and binding energies of the complexes have been determined using Hartree-Fock (HF) and DFT-B3PW91 procedures and different Pople's basis sets as well. The main results are presented and discussed by considering the hydroxyl (OH), amino (NH), and carbonyl (CO) chemical groups of acetaminophen interacting with the acetone or ethanol molecules either separately or in conjunction in the complex formation. The frequency shifts and IR intensity variations associated with the internal modes of acetaminophen (namely nu(OH), nu(NH), and nu(CO)) as well as the most pertinent vibrational probes of ethanol (nu(OH)) and acetone (symmetric nu(CO) and nu(CCC) stretching modes) interacting with acetaminophen have been analyzed. The predicted spectral changes have been critically discussed in comparison with IR absorption measurements of acetaminophen dissolved as a solute in ethanol or acetone CO2 expanded solutions. It is argued that the exchange-correlation contribution taken into account in DFT calculations is likely significant in determining the main IR spectral features of acetaminophen complexes formed with acetone or involving hydrogen-bonded as with ethanol.     

alpha-(Phenylazo)-4-nitrobenzyl cyanide, a new acid-base indicator

A new acid-base indicator, alpha-(phenylazo)-4-nitrobenzyl cyanide, is proposed. The indicator changes colour from yellow to violet in the presence of alkali owing to the formation of a nitronic acid structure. This indicator is applicable for the titration of weak acids in acetone and ethanol media or in a mixture of these organic solvents and water, with 0.1M aqueous sodium hydroxide as titrant. The absorption spectra have been recorded for the indicator in 25%, 50% and 75% aqueous ethanol and acetone. By means of the spectra the dissociation constants in these media have been determined. The pK value of alpha-(phenylazo)-4-nitrobenzyl cyanide is 12.10 in water, and is decreased considerably in acetone but only slightly in ethanol. This behaviour is similar to that of positively charged weak acids and irregular for a weak acid carrying no charge or a negative charge.     

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.      

Peculiar properties of sodium lodide in alcohols,acetone, and alcohol-water mixtures at lower temperatures

The enthalpies of solution of sodium iodide in methanol, ethanol and acetone and in mixtures of methanol and ethanol with water were measured over wide ranges of electrolyte concentration and temperature. Standard enthalpies of solution, transfer enthalpies of NaI from alcohols to alcohol-water mixtures, and temperature coefficients of enthalpies of solution have been calculated. Thermodyanmic characteristics of solution and solvation of the Na⁺ and I^– ions in acetone and ethanol were determined at 243–298 K. It is noted that at lower temperatures the disruption of solvent structure by ions is a local effect. The presence of negative solvation of the Na⁺ and I^– ions in alcohol-water mixtures at lower temperatures is demonstrated.     

Viscosities of Binary and Ternary Mixtures of Water,Alcohol, Acetone,and Hexane

This articles studied and determined the viscosities of the binary mixtures of water–methanol, water–ethanol, water–propanol, water–acetone, acetone–ethanol, methanol–ethanol, and acetone–hexane and the ternary mixtures of water–methanol–ethanol and water–ethanol–acetone at 20°C. It is shown that the mixing of water with the alcohols and acetone resulted in a positive deviation of viscosity, which reached the maximum value at the water mole fraction x ₁ ～ 0.7 for water–methanol, x ₁ ～ 0.72 for water–ethanol, x ₁ ～ 0.74 for water–propanol, and x ₁ ～ 0.83 for water–acetone binary mixture. This viscosity deviation can be mainly attributed to the formation of micelles of alcohol or acetone molecules in water because of the hydrophobic attraction between the hydrocarbon chains. The micelle surfaces are surrounded by hydration layers, leading to the positive viscosity deviation in the liquid mixtures because the water in hydration layers has a much higher viscosity than bulk water. Also, the contrary observation was found in the binary mixtures of acetone–ethanol and acetone–hexane, having a negative viscosity deviation.     

脱模溶剂对制备聚苯乙烯表面大孔材料的影响

采用马来酸酐-醋酸乙烯共聚物乳液为模板,分别以水、乙醇和丙酮为脱模溶剂,合成了表面层(厚度为10μm)为大孔结构(孔径为250～400nm)的聚苯乙烯(PS)孔材料.用扫描电子显微镜(SEM)测定了材料表面的微观形貌,SEM照片显示出3种脱模溶剂均能制备PS大孔材料,其中水为脱模溶剂时对PS基材的不利影响最小.用傅立叶红外光谱仪(FTIR)表征了脱模后孔内被固定的特征基团,结果表明,不同的脱模溶剂分别对应不同的孔内基团,即水-羧基、乙醇-酯基及丙酮-酐基.测定了3种脱模溶剂的脱模速率,其顺序为丙酮>>乙醇>水.     

菠菜叶绿素的浸提和协同萃取反应

有机溶剂;菠菜叶绿素的浸提和协同萃取反应     

Experimental designs characterizing seasonal variations and solvent effects on the quantities of coumarin and related metabolites from Mikania laevigata

Statistical design mixtures of acetone, chloroform, dichloromethane and ethanol were used to study the effects of different solvents and their mixtures on the quantities of coumarin and related metabolites extracted from Mikania laevigata samples harvested in each of the four seasons. RP-HPLC-DAD and both positive and negative modes of UPLC-MS analyses were used to determine relative quantities of coumarin, o-coumaric acid and melilotic acids in each season for all the mixture design extracts. The existence and measurement of the relative abundances of melilotic acid in Mikania laevigata have not been reported previously. Highest coumarin concentrations were encountered in the summer whereas its o-coumaric acid precursor and melilotic acid were most abundant in the spring. O-coumaric and melilotic acids concentrations were strongly correlated during the year. Also solvent effects were seen to be significant. Ethanol and 1:1 binary mixtures of ethanol and acetone extracted the largest quantities of coumarin whereas ethanolic binary and ternary mixtures with chloroform and dichloromethane provided the best yields of o-coumaric and melilotic acids. Statistical mixture models indicated that synergic binary interactions, especially those involving ethanol with acetone or chloroform, are important in the Mikania extraction process.     

Solvent effects on structural properties of SiO2 gel using n-octylamine as a catalyst

We have investigated the effect of solvent(ethanol, acetone, isopropanol) on the sol–gel process of tetraethylorthosilicate (TEOS) in which case, n-octylamine is used as polycondensation catalyst. Two sets of materials were prepared in the laboratory by using ethanol, acetone and isopropanol as solvents respectively: (1) xerogels from TEOS/n-octylamine, and (2) composites from TEOS/polyhedral oligomeric silsesquioxanes /n-octylamine. The chemical structure of xerogels was studied by FTIR, TG–DSC, scanning electronic microscope and nitrogen adsorption–desorption isotherms techniques. The results have shown that the solvents directly influence the gel time. Gel time is longer for acetone than that of ethanol and isopropanol. In the case of TEOS xerogels, the materials are essentially mesoporous when n-octylamine is used as a catalyst. Silica, when ethanol is used as a solvent, exhibits a more narrow pore size showing textures with a microstructure uniformly distributed with different porosity levels. However, when the aged-isopropanol gel is used, silica shows textures with a microstructure nonuniformly distributed.     

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.     

Standard molar enthalpies and volumes of adamantane in methanol,ethanol, acetone,andn-dodecane. Interpretation using the scaled-particle theory

The volumes and enthalpies of solution of adamantane and of cyclohexane in methanol, ethanol, acetone, and n-dodecane have been measured as a function of concentration at 25°C. The standard molar volumes and enthalpies of adamantane have been resolved into cavity and interaction terms. The former have been calculated from the equations of the scaled-particle theory whereas the latter have been deduced from a model which assumes some proportionality between adamantane-solvent and cyclohexane-solvent interactions. The model, which had been previously verified with normal liquids, now also proves to be very satisfactory with solvents involving strong, nonadditive interactions.     

醋酸酯淀粉高取代度的测定

淀粉的乙酰化改性是扩大其应用的一个重要手段。测定醋酸酯淀粉取代度 (DegreeofSubstitution ,简称DS)的方法通常有酸碱滴定法、紫外法、核磁共振法及衰减全反射法[1 ] 等 ,后 3种方法需建立标准曲线 ,要求有一系列取代度的样品 ,实验操作较困难。所以实验室更多采用酸碱滴定法。实验室多采用乙醇为溶剂进行醋酸酯淀粉高取代度的测定[1～3] 。这种方法的缺点是皂化时间需 48～ 72h ,并且高取代度醋酸酯淀粉的溶解性不理想。本文对酸碱滴定法测定醋酸酯淀粉高取代度溶剂选择进行了探讨 ,以期建立一种快速、准确地测定醋酸酯淀粉高取代度的…     

Principal component and Tucker3 analyses of high performance liquid chromatography with diode-array detection fingerprints of crude extracts of Erythrina speciosa Andrews leaves

Mixtures of ethanol, dichloromethane, hexane and acetone obtained according to a statistical design have been used to extract substances from Erythrina speciosa Andrew leaves for chromatographic fingerprinting. The plant extracts from each mixture were analyzed by HPLC-DAD providing UV–vis spectra for each chromatographic peak. These chromatograms and spectra for the design mixtures were then treated with principal component (PCA), Tucker3 and PARAFAC analyses. PCA indicated the existence of five different chromatographic fingerprints for the leave extracts depending on the solvent mixture composition. Different chromatographic peak areas were strongly correlated with the mixture proportions of acetone, dichloromethane and ethanol. Tucker3 and PARAFAC analyses were very useful for identifying simultaneous correlations between chromatographic peak areas, spectral band absorbances and solvent proportions. The acetone proportion was highly correlated with the area of the 3.69 min retention time peak and the spectral absorbances between 250 and 260 nm, consistent with the presence of natural polyphenols. The dichloromethane mixture proportion was strongly correlated with the 12.19 min chromatographic peak area and a single spectral absorbance at 201 nm. This spectral absorption is characteristic of the electronic structures of terpenes and alkaloids.     

Sodium modification of zirconia catalysts for ethanol coupling to 1-butanol

The influences of adding sodium to zirconia on the acid-base properties of the surface and on the catalytic conversion of ethanol and acetone were investigated. The rates of ethanol dehydration, dehydrogenation and coupling were evaluated in a fixed-bed flow reactor operating at temperatures from 613 to 673 K. The rate of acetone condensation was evaluated in the same reactor operating at 473–573 K. Addition of 1.0 wt% Na to ZrO₂ decreased the rate of ethanol dehydration by more than an order of magnitude, which was consistent with a neutralization of acid sites evaluated by ammonia adsorption microcalorimetry. Addition of 1.0 wt% Na to ZrO₂ also increased the base site density quantified by carbon dioxide adsorption microcalorimetry and the rate of acetone condensation. Although the rate of ethanol coupling was not increased by the addition of Na, the overall selectivity of ethanol to butanol was improved over the 1.0 wt% Na/ZrO₂ sample because of the significant inhibition of ethanol dehydration.     

PHOTOCHEMICAL AND FREE RADICAL INITIATED REACTIONS OF 1,3-DIMETHYLTHYMINE WITH ETHANOL

The photochemically induced reaction of 1,3-dimethylthymine (DMT) with ethanol gives four major alcohol adducts. These have been identified as l,3-dimethyl-6-(1-hydroxy-1-ethyl)thymine ( 1 ), 1,3-dimethyl-5-(2-hydroxy-l-pyl)uracil ( 2 ), and the cis and trans isomers of 5,6-dihydro-l,3-di-methyl-6-(l-hydroxy-l-ethyl) thymine ( 3 and 4 ). The compounds 3 and 4 have been shown to be identical to the adducts produced in y-ray irradiated ethanolic aqueous solutions of DMT. Cyclobutane dimers of DMT are also found in the photochemical reaction mixture. Reaction of 1-hydroxyethyl radicals with DMT, initiated by decomposition of di-t-butyl peroxide, leads to formation of the same alcohol adducts, as well as to DMT adducts containing two molecules of ethanol. The acetone sensitized reaction of DMT with ethanol gives 1,3, and 4, along with a variety of adducts incorporating the acetone sensitizer.     

Investigation of polar organic solvents compatible with Corona Charged Aerosol Detection and their use for the determination of sugars by hydrophilic interaction liquid chromatography

A range of organic solvents (ethanol, isopropanol and acetone) has been investigated as alternatives to acetonitrile and methanol when used in conjunction with Corona Charged Aerosol Detection (Corona CAD). These solvents have been evaluated with regard to their effect on the response of the Corona CAD. Three dimensional response surfaces were constructed using raw data showing the relationship between detector response, analyte concentration and percentage of organic solvent in the mobile phase, using sucralose or quinine as the test analyte. The detector response was non-linear in terms of analyte concentration for all solvents tested. However, detector response varied in an approximately linear manner with percentage of organic solvent over the range 0–40% for ethanol or isopropanol and 0–80% for acetone and methanol. The chromatographic performance of the various solvents when used as aqueous–organic mobile phases was evaluated for isocratic and gradient separations of sugars and sugar alcohols by hydrophilic interaction liquid chromatography (HILIC) using an Asahipak NH2P-504E column coupled with Corona CAD detection. It was found that whilst acetonitrile provided the highest column efficiencies and lowest detection limits of the solvents studied, acetone also performed well and could be used to resolve the same number of analytes as was possible with acetonitrile. Typical efficiencies and detection limits of 5330 plates m⁻¹ and 1.25 μg mL⁻¹, respectively, were achieved when acetone was used as the organic modifier. Acetone was utilised successfully as an organic modifier in the HILIC separation of carbohydrates in a beer sample and also for a partially digested dextran sample.     

Photoelectron spectroscopic studies of the adsorption of organic molecules with lone pair orbitals on transition metal surfaces

Ultraviolet and x-ray photoelectron spectroscopy have been employed to investigate the adsorption of methanol, ethanol, diethylether, acetaldehyde, acetone, methyl acetate and methylamine on surfaces of Fe, Ni and Cu. All these molecules adsorb molecularly at low temperatures (≤100 K). Lone pair orbitals of these molecules are stabilized on these metal surfaces (by 0·4–1·0eV) due to molecular chemisorption. The molecules generally undergo transformations as the temperature is raised to 120 K or above. The new species produced seems to depend on the metal surface. Some of the product species identified are methoxy species, formaldehyde and carbon monoxide in the case of methanol and methyl acetate, ethoxy species in the case of ethanol and 2-propanol in the case of acetone. Contribution No. 166 from the Solid State and Structural Chemistry Unit.     

Comparative investigation of zein isolated from gluten by various methods

A comparative study has been made on zein preparations isolated from gluten by extraction with 70% ethanol and precipitation under various conditions; by dialysis, and by the addition of a 0.1 M solution of sodium sulfate or of acetone. An investigation of absorption spectra and of electrophoresis in polyacrylamide gel has shown the advantage of the method using acetone for precipitating the protein preparation.     

Studies on amine hydrothiocyanates. II. Solubilities and heats of solution in some organic solvents

The solubilities of piperidine hydrothiocyanate, piperazine monohydrothiocyanate, ethylenediamine dihydrothiocyanate, and propylenediamine dihydrothiocyanate in some or all of the solvents methanol, ethanol, and acetone have been determined. Linear regression analysis of the solubility data indicates a good fit in each case to the equation in S = (A/T) + B. Heats of solution have been calculated from the linear relationships.     

On the extraction of acids and neptunium from alcoholic and acetonic solutions

The extraction of nitric acid with tridodecylamine (TDA) was studied as a function of methanol, ethanol, isopropanol, and acetone concentration in the aqueous phase. Extraction increases in the order: methanol <ethanol <isoproppanol <acetone. The extraction of nitric acid by TDA is affected by these additives more than the extraction of hydrochloric acid.