Abstract  The UV/visible spectra of 3,4-diphenyl thiophene were obtained in various solvents (both polar and non polar). The wave number of transition energies, corresponding molar absorptivities and oscillation frequency were determined. Three bands were obtained in solvents such as cyclohexane, propan-2-ol, methanol and ether. Two bands are obtained in n-hexane and 1,2-dichloroethane, while 1,4-dioxane give a single band. Transitions are assigned to these bands according to their shift due to the effect of solvents.

Abstract  NOABSTRACT - no abstract found

Abstract  This paper reviews recent experimental results concerning the use of modern excilamps (excimer lamps) in photoscience and photoemical technology. The special characteristics of these sources of incoherent vacuum-UV (VUV)/UV radiation are presented and their applications in water and air remediation are discussed. Special attention is paid to the VUV (172 nm)-initiated oxidation and mineralization of organic water and air contaminants. For example, the VUV-initiated production of carbon dioxide and carbon monoxide during 172 nm irradiation of several saturated volatile organic substrates in the gas phase (e. g. methanol, ethanol, 2-propanol, 1,4-dioxane, cyclohexane, and n-hexane) was quantitatively verified by gas chromatography. Depending on the nature of the gaseous substrate and on the flow rate through the excimer-flow-through photoreactor different CO sub(2)/CO ratios were obtained.Original Abstract: Cet article revoit les recents resultats experimentaux sur l'utilisation d'excilampes (lampes excimeres) modernes dans la technologie de la science photoelectrique et photochimique. Les caracteristiques speciales de ces sources de rayonnement incoherent sous vide UV (VUV)/UV sont presentees et leur utilisation pour la rehabilitation de l'eau et de l'air est abordee. Une attention speciale est apportee a l'oxydation et a la mineralisation initiees par VUV (172 nm) des contaminants organiques dans l'eau et l'air. Par exemple, la production de dioxyde de carbone et de monoxyde de carbone initiee par VUV au cours d'une radioexposition a 172 nm dans plusieurs substrats organiques volatils satures dans la phase gazeuse (p. ex. methanol, ethanol, propan-2-ol, 1,4-dioxane, cyclohexane et n-hexane) a ete verifiee quantitativement par chromatographie en phase gazeuse. Differents rapports CO sub(2)/CO ont ete obtenus selon la nature du substrat gazeux et selon le debit a travers le photoreacteur excimere a ecoulement continu. Mots-cles : lampes excimeres, excilampes, radioexposition a 172 nm, oxydation aux ultraviolets du vide, photomineralisation, desinfection aux UV, photoreacteur excilampe a circulation d'echantillon, photoreacteur a ecoulement piston, photo-oxydation en phase gazeuse.[Traduit par la redaction]

Abstract  The influence of a resident stereocenter on the formation of hydroperoxy acetals from carbonyl oxides is investigated. Addition of either methanol or 2-propanol to 8-phenylpropanal O-oxide proceeds with modest stereoselectivity; addition of a tertiary alcohol proceeds with higher selectivity. Product stereochemistry, which is confirmed by conversion of a functionalized hydroperoxy acetal to a 1,2-dioxane, is found to derive from nucleophilic attack through a Felkin-Anh type transition state. Trapping of a carbonyl oxide containing a neighboring hydrogen bond donor proceeds with modest selectivity for both syn- and anti-carbonyl oxide isomers. Ozonolysis of a 3-(trialkylstannyl)-1-enol ether proceeds with loss of the stannyl-bearing carbon through the possible intermediacy of a vinyl peroxide.<

Abstract  A new dual fluorescent N,N-dimethylaniline derivative, sodium 4-(N,N-dimethylamino)benzenesulfonate (SDMAS), is reported. In SDMAS, the electron acceptor is linked to the phenyl ring via a sulfur atom at the para-position of the electron donor. It was found that SDMAS emits dual fluorescence only in highly polar solvent water but not in organic solvents such as formamide, methanol and acetonitrile. In organic solvents only a single-band emission at ca.360 nm was observed in the short wavelength region. The dual fluorescence of SDMAS in water was found at 365 and 475 nm, respectively. Introduction of organic solvent such as ethanol, acetonitrile, and 1,4-dioxane into aqueous solution of SDMAS leads to blue-shift and quenching of the long-wavelength emission. Measurements of steady-state and picosecond time-resolved fluorescence indicate that the long wavelength fluorescence is emitted from a charge transfer (CT) state that is populated from the locally excited (LE) state, with the latter giving off the short wavelength fluorescence. The fact that a highly polar solvent is required to bring out the dual fluorescence suggests that the CT process of SDMAS has a high activation energy (E-a). In supporting this assumption the time-resolved fluorescence measurements give an E-a of 15.35 kJ . mol(-1). It was assumed that the participation of the sulfur atom d-orbital in the conjugation of sulfonate group with phenyl ring and the strong twisting and inverting of the dimethylamino plane relative to the phenyl ring could be the reasons for the high activation energy. A molecular configuration change upon charge transfer in water was suggested for SDMAS based on the thermodynamic data. SDMAS reported here represents the example of the dual fluorescent amine substituted aromatic sulfonate.<

Abstract  Methyl 3,5-dioxohexanoate (1) reacts with hydrazines (2) in methanol or acetic acid to give a mixture of the isomeric pyrazolylacetates (3) and (4), whose molar ratio depends on the solvent and hydrazine. 2,2-Dimethyl-5-(1-hydroxy-3-oxobutylidene)-1,3-dioxane-4,6-dione (5) reacts chemoselectively with hydrazines to give the 5-pyrazolylacetates (3) as the only reaction products.<

Abstract  NOABSTRACT - no abstract found

Abstract  Oxygenated compounds like methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetaldehyde, crotonaldehyde, ethylene oxide, tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, and 2-chloromethyl-1,3-dioxolane are commonly encountered in industrial manufacturing processes. Despite the availability of a variety of column stationary phases for chromatographic separation, it is difficult to separate these solutes from their respective matrices using single dimension gas chromatography. Implemented with a planar microfluidic device, conventional two-dimensional gas chromatography and the employment of chromatographic columns using dissimilar separation mechanisms like that of a selective wall-coated open tubular column and an ionic sorbent column have been successfully applied to resolve twelve industrially significant volatile oxygenated compounds in both gas and aqueous matrices. A Large Volume Gas Injection System (LVGIS) was also employed for sample introduction to enhance system automation and precision. By successfully integrating these concepts, in addition to having the capability to separate all twelve components in one single analysis, features associated with multi-dimensional gas chromatography like dual retention time capability, and the ability to quarantine undesired chromatographic contaminants or matrix components in the first dimension column to enhance overall system cleanliness were realized. With this technique, a complete separation for all the compounds mentioned can be carried out in less than 15min. The compounds cited can be analyzed over a range of 250ppm (v/v) to 100ppm (v/v) with a relative standard deviation of less than 5% (n=20) with high degree of reliability.

Abstract  Acoustical and volumetric properties have been measured for substituted heterocyclic compounds digoxin and thiabendazole in 1, 4 dioxane at 303 K. The ultrasonic velocity measurement have been performed to evaluate acoustical parameter such as adiabatic compressibility (beta s), partial molal volume (phi(v)), intermolecular free length (L(f)), apparent molal compressibility (phi(kappa)), specific acoustic impedance (Z), relative association (R(A)), salvation number (Sn), limiting apparent molal compressibility (phi(0)(kappa)), limiting apparent molal volume(phi(0)(v)) and their constant (S(k),S(v)). The viscosity coefficient (A, B) was evaluated by using john-dole equation. These parameters throw the light on the solute-solvent interaction and solute-solute interaction.

Abstract  Vicinal (1)H--(1)H coupling constants were used to determine the conformational preferences of 2,3-dihydroxypropanoic acid (1) (DL-glyceric acid) in various solvents and its different carboxyl ionization states. The stereospecific assignments of J(12) and J(13) were confirmed through the point-group substitution of the C-3 hydrogen with deuterium, yielding rac-(2SR,3RS)-[3-(2)H]-1, and the observation of only J(13) in the (1)H NMR spectra. While hydrogen bonding and steric strain may be expected to drive the conformational equilibrium, their role is overshadowed by a profound gauche effect between the vicinal hydroxyl groups that mimics other substituted ethanes, such as 1,2-ethanediol and 1,2-difluoroethane. At low pH, the conformational equilibrium is heavily weighted toward the gauche-hydroxyl rotamers with a range of 81% in DMSO-d(6) to 92% in tert-butyl alcohol-d(10). At high pH, the equilibrium exhibits a larger dependence upon the polarity and solvating capability of the medium, although the gauche effect still dominates in D(2)O, 1,4-dioxane-d(8), methanol-d(4), and ethanol-d(6) (96, 89, 85, and 83% gauche-hydroxyls respectively). The observed preference for the gauche-hydroxyl rotamers is believed to stem primarily from hyperconjugative sigma(C--H) --> sigma*(C--OH) interactions.

Abstract  The mechanism of membrane interaction by beta-sheet peptides is important to understand fundamental principles of folding of beta-barrel proteins and various beta-amyloid proteins. Here, we examined the conformational characteristics of a porin-like channel forming (xSxG)(6) peptide in solution and membrane-mimicking environments (CD and ATR-IR) to understand the structural changes of the peptide during membrane association and channel formation. A comparison of the peptide conformations in different microenvironments showed that beta-sheet formation is enhanced in membrane-mimicking liposomes and SDS-micelles. The lipid-induced beta-sheet formation was confirmed by the formation of a characteristic beta-sheet structure on mixing a methanolic solution of the peptide (partially folded) with preformed liposomes. The amphipathicity of the peptide; increased hydrogen bonding, hydrophilicity, and reduction in dimensionality of the membrane surface; membrane-peptide interaction-forces; and presence of flexible glycines might facilitate beta-sheet formation in membranes. Though the CD spectra of both the peptide-bound and peptide-incorporated lipids are reminiscent of a beta-sheet structure, a significant variation in the peak positions of the two beta-sheet structures was noticed. The channel characteristics of (xSxG)(6) in the presence of low ionic strength solutions of NEt(3)BzCl and glucosammonium chloride are comparable to those reported under high ionic strength solutions. Altogether the data suggest that the channel formation by (xSxG)(6) proceeds via beta-sheet aggregate formation at the membrane surface, beta-sheet insertion, and rearrangement into a beta-barrel-like structure. The beta-barrel-like channel formation most likely arises from a sequence similarity to beta-barrel porins whereas the lipid-induced beta-sheet formation is governed by the above-mentioned factors.

Abstract  The ultrasonic velocity (U), density (rho) and viscosity (eta) at 303 K have been measured in the binary system of phenol in dioxane, methanol and acetonitrile. The acoustical parameters such as adiabatic compressibility (beta), free length (L(f)), free volume (V(f)), internal pressure (pi(i)), Wada's constant (W), Rao's constant (R) and acoustical impedance (Z) are calculated. The results are interpreted in terms of molecular interaction between the components of the mixtures.

Abstract  N-14 chemical shifts of neat quinoline and 90% quinoline in different solvents have been measured. DMSO-d(6) was used as an internal locking agent NH4NO3 wits used as an external standard. The N-14 chemical shift of neat quinoline with respect to NO3. ion is -71.75 ppm previously reported N-14 chemical shifts by this group in pure quinoline was -72 +/- 2 ppm in external lock mode. The internal lock result are more accurate. The chemical shifts of 90% quinoline in carbon tetrachloride, chloroform and dioxane are nearly the same i.e -71.57, -73.61 and -70.14 ppm respectively.The N-14- chemical shifts of 90% quinoline in water and methanol are relatively low i.e. -135.87 and -109.96 ppm respectively. This is due to hydrogen-bonding of nitrogen with water and methanol. In DMSO and acetone the N-14 chemical shifts are - 63.41 and -62.78 ppm respectively. This may be due to complex formation of these compounds with quinoline. In all such cases N-14 studies has been done at a frequency of 6.43 MHz using JEOL FX 90Q FT NMR. To avoid the base line rolling due to low frequency and acoustic ringing a delay time of 400 mus has been used.<

Abstract  (no abstract)

Abstract  Steady-state and time-resolved fluorometry, quasielastic light scattering, and viscometry were used to study solution behavior of fluorescently tagged poly(methyl methacrylate) (PMMA) in binary mixtures of 1,4-dioxane with either 2,2,3,3-tetrafluoropropanol (TFP) or methanol. In 1,4-dioxane/TFP mixtures, which are good solvents for PMMA, an intermolecular association occurs. It was shown by time-resolved fluorometric measurements that the unusual behavior of PMMA in good solvent mixtures is due to association of nonpolar fluorophores in a polar medium. Association processes were not detected in systems containing a virtually identical, but nontagged PMMA sample in the same solvent mixtures. In mixed solvents of 1,4-dioxane/methanol, association of the tagged (as well as nontagged) sample does not take place.

Abstract  In order to observe more directly the structural organization of water molecules around an apolar molecule in an aqueous solution, supercooling phenomena and enthalpies of mixing with various solvents have been examined using aqueous solutions of tetrabutylammonium (or isopentylammonium) chloride subjected to different thermal treatments. Solution I was kept at a temperature only one degree higher than its dissolution temperature, at which a hydrate crystal phase was completely dissolved. The temperature of solution II was raised to 80 degrees C. The supercooling temperatures of solution I were found to be rather higher than those of solution II: 10-15 degrees C for (n-C4H9)(4)NCl and about 20 degrees C for (i-C5H11)(4)NCl, regardless of the concentrations of these salts. The differences of the enthalpies of mixing between solution I and solution II in the same solvent Delta H-I - Delta H-II were determined. It was found that, (1) for solvents such as acetone, tetrahydrofuran, and 1, 4-dioxane, Delta H-I - Delta H-II values were about 10 kJ per mole of (n-C4H9)(4)NCl which contained 49 moles of water (i.e. the mole fraction of a sample solution was 0.02), and (2) when the solvents were alcohols (methanol and ethanol), the Delta H-I - Delta H-II value became rather small and in the case of water the Delta H-I - Delta H-II value became even smaller (1.1 kJ mol(-1)). It is concluded that the difference in the stability of water networks between solutions I and II is 0.204 kJ per mole of water, which corresponds to about 3.4% of the enthalpy of fusion of ice I.<

Abstract  Khasare's equation of state has been applied to the binary liquid mixture system of acrolein in methanol, cyclohexane and p-dioxane. It is observed that there is a close agreement with experimental one. The thermodynamic picture built up in this formulation could be considered as a good representation of molecular clusters.<

Abstract  Electronic absorption and fluorescence excitation and emission spectra of four acridines (acridine, Acridine Yellow, 9-aminoacridine and proflavine) and three phenazines (phenazine, neutral Red and safranine) are determined at room temperature (298 K) in several solvents of various polarities (dioxane, chloroform, ethyl ether, ethyl acetate, 1-butanol, 2-propanol, ethanol, methanol, dimethylformamide, acetonitrile and dimethyl sulfoxide). The effect of the solvent upon the spectral characteristics of the above compounds, is studied. In combination with the ground-state dipole moments of these compounds, the spectral data are used to evaluate their first excited singlet-state dipole moments by means of the solvatochromic shift method (Bakhshiev's and Kawski-Chamma-Viallet's correlations). The theoretical ground and excited singlet-stare dipole moments for acridines and phenazines are also calculated as a vector sum of the pi-component (obtained by the PPP method) and the sigma-component (obtained from sigma-bond moments). For most acridines and phenazines under study, the experimental excited singlet-state dipole moments are found to be higher than their ground state counterpart. The application of the Kamlet-Abboud-Taft solvatochromic parameters to the solvent effect on spectral properties of acridine and phenazine derivatives is discussed.<

Abstract  A spectrophotometric method for the determination of palladium, tellurium and iridium from nitric acid media after extraction of their 2-mercapto-4-methyl-5-phenylazopyrimidine complexes into molten naphthalene has been develop and possible synergistic effects have been investigated. Dioxane, methanol, ethanol, l-propanol, acetone and acetonitrile are used as the organic component of the mixed (polar) phase; the maximum enhancement is obtained with acetonitrile. Solid naphthalene containing the metal complex is separated by filtration and dissolved in chloroform; trace amounts of these metals are determined spectrophotometricaly. Beer's law is obeyed in the following concentration ranges: Pd, 7.0-84.0 mu g; Te, 10.0-125.0 mu g and Ir, 6.0-90.0 mu g/ 10 ml of the final solution. The molar absorptivities (dm(3) mol(-1) cm(-1)) and Sandell's sensitivities (mu g cm(-2)) were calculated: Pd(II)=2.05X10(4) and 0.0052, Te(IV)=1.84X10(4) and 0.0069 and Ir(III)=0.95X10(4) and 0.020, respectively. Ten replicate analyses containing 12.5 mu g of Pd(II), 21.0 mu g of Te(IV) and 85.0 mu g of Ir(III) gave mean absorbances of 0.241, 0.302 and 0.420 with relative standard deviations of 0.53, 0.36 and 0.85%, respectively. The interference of various ions was studied, and conditions were developed for the determination of these metals in certain alloys and synthetic mixtures.<

Abstract  On the basis of the concept of local composition, a new model is proposed for correlating the Raman frequency shifts of a C-H stretching band over the whole concentration with only one energy parameter. Mixtures investigated include water + acetone, water + 2-propanol, water + N,N-dimethylformamide (DMF), water + methanol, water + ethanol, water + 1,4-dioxane, water + dimethyl sulfoxide (DMSO), and water + acetonitrile systems. The vapor-liquid equilibrium data were predicted by the parameter obtained from the spectra and one activity coefficient at infinite dilution. In this way, the spectroscopic information can be,related to thermodynamic properties.

Abstract  Convenient and preparative synthetic procedures of 2,4,6-tris(chlorosulfonyl)- and 2,4,6-tris(fluorosulfonyl)phenol, -chlorobenzene and -aniline have been elaborated. Chlorine exchange for fluorine by KF interaction on 2,4,6-tris(chlorosulfonyl)aniline and especially 2,4,6-tris(chlorosulfonyl)phenol proceeds easily and selectively under anhydrous conditions in dioxane. Unlike, 2,4,6-tris(chlorosulfonyl)chlorobenzene transformation requires the presence of water. On the basis of 2,4,6-tris(fluorosulfonyl)phenol and some of its salts, XRD measurements demonstrated the structural similarity to picric acid and its derivatives in the solid state.

Abstract  A novel cation exchange fiber supported solid membrane was developed for transport of cobalt, manganese and nickel metal ions. Fiber supported solid membrane was prepared by chemically modifying the cellulose fibers with citric acid. In the fiber supported solid membrane, the diffusion by capillary action by keeping the liquid phase in the porous solid fiber and ion exchange mechanism were used for the effective transport of metal ions. The experimental variables examined were concentration of metal ions (10(-2) to 10(-4) mol L-1) in the source solution, mixed solvent composition (phi = 20 % TBP, acetone or tetrahydrofuran or 1,4-dioxane or methanol or ethanol or 2-propanol 10 to 60 % and HCl (1 to 2 mol L-1) in the receiving phase and stirring speed (40-120 rpm) of the bulk source and receiving phase. The enrichment of concentration of cobalt, manganese and nickel metal ions was observed from the dilute solutions.

Abstract  A monohydrate, and three solvates of a metabolite of an antibacterial agent, sulfamerazine, N-4-acetylsulfamerazine (NSMZ), were identified and characterized by nuclear magnetic resonance spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and single crystal X-ray diffraction. The solvates were obtained with the solvents: acetic acid, methanol, and 1,4-dioxane. All the crystal structures belong to the triclinic. P (1) over bar space group. Analysis of hydrogen bonding in the crystal structures revealed that the NSMZ molecules form a dimer via a pair of intermolecular N-H center dot center dot center dot N hydrogen bonds. These dimers are interconnected to each other via the solvent molecules forming extended hydrogen bonded networks. The conformations of the NSMZ in the hydrate/solvates are found to be significantly different. Thermal analysis established the stability and confirmed molar ratios of the reported hydrate/solvates, whereas crystal lattice energies and competitive crystallization experiments confirmed the stability of methanol solvate over the hydrate and other solvates. (C) 2011 Elsevier B.V. All rights reserved.

Abstract  Abstract: We report the effects of polar-protic and polar-aprotic SOLVENT*s on absorption spectra and particle size of surfactant stabilized silver nanoparticles. Cysteine and cetylteimethylammonium bromide, CTAB were used as the reducing and stabilizing agents, respectively. The prepared orange color silver sols possess an unusually narrow Plasmon absorption shoulder at 450nm. The absorbance and shape of this shoulder are affected by protic (methanol, ethanol) and aprotic (acetonitrile, DMF, DMSO and 1,4-dioxane) SOLVENT*s. The observed results are interpreted in terms of the dielectric constant, boiling point, hydrogen bonding, solubilization and donation of electron density from the silver particles to the SOLVENT*s. Absorbance increases with increasing the dielectric constants of reaction mixture. The particle size decreases with decreasing the hydrophobic character of protic SOLVENT*s: particle size=70, 58 and 39nm in presence and absence of SOLVENT*s (ethanol and methanol), respectively. ds: Internet resource her supplied data e field[29]: 1,4-Dioxane

Abstract  An ultraviolet spectrometer was used to measure the absorption kinetics of a laser dye, 1,4-bis(5-phenyloxazoyl-2-yl) benzene, at its maximum wavelength in solutions of styrene-acrylonitrile copolymer dissolved in 1,4-dioxane. From the time-dependent absorbance data, the dye diffusion coefficient was calculated by a combination of Fick's law of diffusion with the Beer-Lambert law of absorption. (C) 2005 Wiley Periodicals, Inc.