Dilute Benzene Solutions Research Articles

Study of dielectric relaxation mechanism and thermodynamic parameters of binary mixtures of N-methylformamide and dimethylsulphoxide in dilute solution of benzene

Study of dielectric relaxation mechanism and thermodynamic parameters of binary mixtures of N-methylformamide and dimethylsulphoxide in dilute solution of benzene

Computational and experimental studies on dielectric relaxation and dipole moment of some anilines and phenol

In the present study, the dielectric relaxation behaviour of four polar molecules namely 2-Nitroaniline, 4-Bromoaniline, 4-Chloroaniline and 4-Chlorophenol were studied in dilute solutions of benzene using microwave bench at 9.59GHz frequency. The different parameters like, dielectric constant (ε′), dielectric loss (ε″), static dielectric constant (ε0) and optical permittivity (ε∞) have been determined. Further from these values, dipole moment (μ) and relaxation time (τ) were calculated for all the molecules following Gopalkrishna, microwave conductivity and the Higasi method. The dipole moment for all the molecules were also estimated theoretically from ab initio computations by using Density Functional Theory (DFT) calculations with the help of Gaussian 09W software. Dipole moments determined experimentally and through DFT computations are in good agreement with the dipole moments estimated by taking vector sum of group moments of Aniline, Nitrobenzene, Bromobenzene, Chlorobenzene and Phenol by neglecting interaction between pendant groups. The experimentally determined relaxation times were analyzed in terms of Stokes-Einstein-Debye (SED) theory and the results are compared with molecular radii estimated from DFT and Edward's atomic increment methods. Further, in order to understand the chemical stability and reactivity of all these molecules, highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) and HOMO-LUMO energy gap were also estimated from DFT computations. Our experimental findings suggest that, 2-Nitroaniline exhibits simple Debye type relaxation behaviour while the other three samples exhibit Higasi's distribution of relaxation times which may be due to both overall and intra-molecular rotation of the molecules. Further, the HOMO-LUMO studies revealed that, 2-Nitroaniline is more chemically reactive having least energy gap and 4-Chlorophenol is least chemically reactive having highest energy gap among the four samples.

Study of Dielectric Relaxation Time and Thermodynamic Parameters in Some Polar Molecules in dilute solution of Benzene

Study of Dielectric Relaxation Time and Thermodynamic Parameters in Some Polar Molecules in dilute solution of Benzene

Activation energy (ΔG*), enthalpy (ΔH*), and entropy (ΔS*) of poly(ethylene glycol) using Higasi method

The change in free energy of activation (\(\Delta G_{\tau }^{*}\)), enthalpy of activation (\(\Delta H_{\tau }^{*}\)), and entropy of activation (\(\Delta S_{\tau }^{*}\)) of poly(ethylene glycol) with average molecular mass 400 Dalton (PEG 400) in dilute solutions of benzene have estimated based on the theory of Eyring rate process. These thermodynamic parameters have been determined using most probable dielectric relaxation times (τ) at different temperatures using Higasi method. Based on the results, the behavior of the stated polymer in non-polar solvent is discussed. The obtained results are compared with those determined using Whiffen and Thompson model.

MOLECULAR INTERACTION ANALYSIS OF POLAR LIQUIDS ACETONITRILE, ACEOPHENONE, 2-PROPANOL IN NON-POLAR BENZENE SOLVENT TREATED WITH MICROWAVE FREQUENCY

The study of dielectric liquid behaviour under diff erent exposure is one of the most fascinating front iers in solid state physics. It has undoubtedly render considerable service to ever y physicist doing research in this field. The incr easing desire to understand the molecular interactions have led to conduct the present study, which deals with a certain group of polar compounds such as (i) Acetonitrile (AN), (ii) Acetophenone (AP) and (iii) 2-Propanol (2-P) with a non-polar compound benzene . The dielectric behaviour of individual compound, binary mixtures atheir ratios have been studied at microwave freq uency of 21.68GHz in non-polar solvent (benzene) at constant temperature 300K. Different dielectric parameters like dielect ric constant e’ and dielectric loss e” at microwave frequency, static dielectric constan t es at 1 KHz frequency, dielectric constant e∞ at optical frequency have been determined. Using these dielect ric data, dipole moment µ, various relaxation time viz (i) molecular relaxation time τ(1) (ii) overall relaxation time of a molecule τ(2) and (iii) average relaxation time τ(υ), distribution parameter (α) of individual compound, binary mixtures and their rati os in dilute solutions of benzene also have been de termined experimentally. Weight fraction method is used for changing the con centration of solute in solvent. The observed resu lts are discussed on the basis of various types if relaxation processes, whi ch change with the size, shape and type of interact ion.

Microwave Dielectric Relaxation of Alcohols in non polar solutions

The properties of the binary mixtures of 1-propanol and phenol have been studied at constant temperature 303K in dilute solutions of benzene using standard standing wave microwave X-band (9.4 GHz) Jband (7.4 GHz) technique. The values of different dielectric parameters e0, e', e'', e∞ have been determined for five different mole fractions of 1-propanol and phenol. The values of permittivity and dielectric loss are used to evaluate relaxation time for overall molecular rotation (τ1), relaxation time for intermolecular rotations (τ2), most probable relaxation time (τ0) and dipole moment (μ) at constant temperature 303K. The values of relaxation times and dipole moment are found to increases with the mole fraction of 1-propanol, phenol in all binary mixtures. The energy parameter (ΔFτ) for dielectric relaxation process of the mixtures is also calculated. It is found that the dielectric relaxation process can be treated as a rate process. The present investigation suggest that existence of both the intermolecular and intramolecular orientation takes place in both binary mixtures.

Synthesis and properties of axially BODIPY conjugated subphthalocyanine dyads

The treatment of boron(III) subphthalocyanine chloride with borondipyrromethene derivatives containing either one or two [4-(N,N-dimethylamino)phenyl]ethenyl groups in toluene gave the corresponding axially substituted boron(III) subphthalocyanine dyes. The novel borondipyrromethene–subphthalocyanine dyes were fully characterized by mass spectrometry, UV–Vis, 1H and 13C NMR spectroscopy as well as elemental analysis. The photophysical properties of title compounds were investigated by means of absorption and fluorescence spectroscopy in dilute benzene solutions. The new dyads exhibited a highly efficient energy transfer process from the excited subphthalocyanine unit to the borondipyrromethene unit. The singlet oxygen generation ability of these dyads was also investigated in dimethylsulfoxide for determination of possibility of these compounds for photodynamic therapy of cancer.

Electro-optical Properties, Polarity and Chain Rigidity of Poly(dialkoxyphosphazene)s with Variable Side-Chain Length

Molecular properties of poly(dialkoxyphosphazene) (PDAOP) series with the aliphatic side-chains contained 3, 4, 6, and 7 carbon atoms were investigated in dilute benzene solutions by techniques of electro-optical Kerr effect and dynamo-optical Maxwell effect, and by dielectric spectroscopy. The sign inversion of Kerr effect and Maxwell effect in PDAOP solutions from positive to negative was detected at the side-chain length range of 5–6 carbon atoms. These phenomena were explained by the strong dependence of anisotropy of optical polarizability of PDAOP monomeric unit on chemical structure and change of its sign at the indicated side-chain lengths. It was demonstrated that PDAOPs possess a critical side-chain-length interval at which their physical properties, depending on the intramolecular ordering, display a singularity. It was also shown that the studied PDAOP samples are not flexible-chain polymers. They are characterized by Kuhn segment 47–65 A, the value of which increases with the elongation of aliphatic side-chain. Dielectric properties of PDAOP were correlated to the properties of the macromolecules with manifestation of kinetic rigidity under a treatment of electric field.

The mechanism of oxidative addition of iodine to a dimethylplatinum(II) complex

The oxidative addition of iodine to [PtMe2(bipy)], 1, occurs easily with trans stereochemistry to give trans-[PtI2Me2(bipy)], 2a, which then equilibrates slowly with cis-[PtI2Me2(bipy)], 2b. The structures of 2a and 2b were determined in a crystal containing both isomers and an additional iodine molecule. Low temperature NMR studies show that an intermediate charge transfer complex [PtMe2(I2)(bipy)], 3, or solvated iodine complex [PtMe2(I2)(S)(bipy)], S = solvent, may be formed in dichloromethane or acetone solution before formation of 2a. In dilute benzene solution, as monitored by UV–visible spectroscopy, the rearrangement of the intermediate complex to 2a followed first order kinetics, and exhibited a large negative entropy of activation, as expected if cleavage of the I–I bond to give an ionic intermediate [PtIMe2(bipy)]+I−, is rate determining. The overall reaction is slower in more polar solvents because, although the I–I bond is more easily cleaved to give [PtIMe2(bipy)(S)]+I−, the subsequent displacement of solvent, S, by iodide to give 2a is slow.

Thermodynamic parameters of poly(ethylene glycol) from dielectric relaxation studies

AbstractThermodynamic parameters, like change in free energy of activation (ΔG), enthalpy of activation (ΔH), and entropy of activation (ΔS) of poly(ethylene glycol) with average molecular mass 400 Delton (PEG 400) in dilute solution of benzene were computed on the basis of theory of Eyring rate process. To estimate these, the dielectric relaxation time (τ), determined at various temperatures adopting Whiffen and Thompson model have been used. X‐band microwave bench working at 9.59 GHz was employed to find temperature dependent real part ε′ of the complex dielectric permittivity ε* and dielectric loss ε″. The values of these ε′ and ε″ are used to find τ values. Based on the results reported, the relaxation behavior of the stated polymer in nonpolar solvent is discussed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Temperature Dependence Studies on Dielectric Relaxation and Electric Dipole Moment of Poly (Ethylene Glycol)

Temperature dependant studies of dielectric relaxation time τ and electric dipole moment μ of poly (ethylene glycol) (PEG) with molecular weight 400 in dilute solution in benzene was carried out at 9.59 GHz at different temperatures using an X-band microwave bench. GopalaKrishna's single frequency and concentration variation method were adopted to determine τ and μ. Results are reported and discussed. On the basis of these parameters, the dielectric behavior of PEG-400 in a nonpolar solvent is discussed.

Dipole moment studies of complexes of alcohols with ethyl bromide

The experimental values of the dipolar increment of the complexes of ethyl bromide with p-cresol, cyclohexyl alcohol, butyl alcohol, and propyl alcohol in dilute solutions of benzene have been measured at a temperature of 308 K. Dipolar incremental values of the systems were calculated using Huyskens method based on Onsager′s theory. Some problems related to the dipole moment enhancement (Δ μ) caused by hydrogen bond formation between donor and acceptor molecules are discussed.

Unusual Luminescence Enhancement of Metallogels of Alkynylplatinum(II) 2,6-Bis(N-alkylbenzimidazol-2′-yl)pyridine Complexes upon a Gel-to-Sol Phase Transition at Elevated Temperatures

A series of alkynylplatinum(II) complexes of 2,6-bis(N-alkylbenzimidazol-2'-yl)pyridine has been synthesized and characterized by (1)H NMR, IR, FAB mass spectrometry, and elemental analysis; the photophysical properties have also been investigated. All the complexes have been shown to exhibit interesting gelation properties. Scanning electron microscopy (SEM) of the xerogels showed a network of fibrous structures, typical of morphologies of organogels/metallogels. Interestingly, two of the complexes were found to show strong luminescence enhancement upon a gel-to-sol phase transition upon increasing the temperature. This unusual behavior is rarely encountered, as it represents a sharp contrast to that exhibited by other typical thermotropic organogels and metallogels reported so far. Variable-temperature UV-vis and luminescence spectroscopies were performed to probe the gel-to-sol phase transition. Concentration-dependent, variable-temperature, and time-resolved emission studies in dilute benzene solution have also been made to provide further insights into the spectroscopic origin in the sol forms. A quantitative treatment of the system based on the Birks scheme has been performed.

Solution behavior of ethylcellulose in organic solvents

Ethylcellulose has been investigated by osmotic pressure, sedimentation-diffusion, and light scattering measurements in dilute solutions of acetone, ethylacetate, 2-butanol, n-butylchloride, and benzene. Combining the results of different measuring techniques allowed the recognition and elimination of the influence of microgels present in the solution. The observed second virial coefficients are high as compared with those of the vinyl polymers and do not show a pronounced dependence on the type of solvent. On the other hand, the radius of gyration is nearly proportional to the root of the molecular weight. This behavior is discussed in connection with results on other cellulose ethers reported in the literature.

Hydrodynamic, electrooptical, and conformational properties of fullerene-containing poly(2-vinylpyridines) in solutions

For C60 fullerene-containing poly(2-vinylpyridines) synthesized by anionic polymerization, the molecular mass and hydrodynamic size of macromolecules in solutions have been determined by molecular hydrodynamics (translational diffusion and viscometry) and electrooptics in dilute benzene and THF solutions. Under the same conditions in the molecular mass range (9.8–123) × 103, the hydrodynamic behavior of linear poly(2-vinylpyridines) and their molecular-mass dependences have been examined and the conformational characteristics of macromolecules have been established. The branching of macromolecules has been characterized by comparing the properties of star-shaped fullerene-containing and linear poly(2-vinylpyridines). With consideration of the hydrodynamic data interpreted within the framework of regular star model, it is inferred that on average three to four linear polymer chains with a molecular mass of (8 ± 3) × 103 for each chain are attached to a fullerene core of C60 in molecules of fullerene-containing poly(2-vinylpyridines). The specific Kerr constant of fullerene-containing poly(2-vinylpyridines) in dilute benzene solution is −(14 ± 1) × 10−12 cm5/[g (300 V)2]. As evidenced by the electrooptical data, the incorporation of fullerene into the polymer weakens self-association of macromolecules in solution.

Water-methanol-benzene ternary system. Thermochemical experiment and computer simulation

Solution heats have been measured for benzene dissolved in mixtures of water with methanol at 25°C. The resulting values are compared with data for water-methanol-aniline, water-acetonitrile-benzene, and water-acetonitrile-aniline systems. Computer simulations have been performed for binary mixtures of water with methanol and dilute solutions of benzene in these mixtures. Thermodynamic and structural characteristics of solutions were obtained by calculations. The enthalpy of benzene transfer from water into a mixed solvent correlates with the relative deviation of the local composition from the mean composition of the mixture.

Dielectric relaxation study of 1-propanol, benzonitrile and their mixtures at microwave frequency

The dielectric absorption of 1-propanol, benzonitrile and their mixtures over a wide range of concentrations has been studied at microwave frequency in dilute solutions of benzene. Dielectric constant ∈′ and dielectric loss ∈ʺ at microwave frequency 9.1 GHz, static dielectric constant ∈ 0 at 455 kHz frequency and dielectric constant ∈ ∞ at optical frequency have been determined for dilute solutions of the polar solutes in benzene. The dielectric data in dilute solutions were used to evaluate relaxation time τ 0 and distribution parameter α of the components and their binary mixtures using Higasi's single frequency method.

Effects of Fluorine-Containing Graft and Block Copolymer Additives on Removal Characteristics of Dilute Benzene in Water by Microphase-Separated Membranes Modified with These Additives

This paper focuses on the effects of the addition of fluorine-containing graft or block copolymer additives composed of 1H,1H,2H,2H-heptadecafluorodecyl acylate (perfluoroalkyl acylate, PFA) and poly(dimethylsiloxane) macromonomer (PDMS) or PDMS macro-azo-initiator to a microphase-separated membrane consisting of PDMS and poly(methyl methacrylate) (PMMA) on the benzene/water selectivity for an aqueous dilute benzene solution during pervaporation and the surface characteristics and structures of the surface-modified PMMA/PDMS membranes. The addition of the fluorine-containing copolymer additives, PFA-g-PDMS and PFA-b-PDMS, to a PMMA-g-PDMS membrane yielded hydrophobic surfaces at the air side of surface-modified membranes due to the localization of their additives on the air-side surface of these membranes. The addition of a small amount of the PFA-g-PDMS and PFA-b-PDMS enhanced both the benzene/water selectivity and the permeability for an aqueous dilute benzene solution during pervaporation because of the formation of their hydrophobic surfaces and the existence of the microphase-separated structures with a continuous PDMS phase in the inner of these membranes. When larger amounts of the PFA-g-PDMS and PFA-b-PDMS were added to a PMMA/PDMS, the latter additive could keep the microphase-separated structures with a continuous PDMS phase, but the former did not. The relationship between the permeation and separation characteristics for the removal of benzene from an aqueous benzene solution and the structures the PMMA-g-PDMS membranes surface-modified with PFA-g-PDMS and PFA-b-PDMS as fluorine-containing polymer additives is discussed in detail.

A comparative study of non-polar solvents effect on dielectric relaxation and dipole moment of binary mixtures of mono alkyl ethers of ethylene glycol and of diethylene glycol with ethyl alcohol

Dielectric relaxation and dipole moment of binary mixtures of homologous series of mono alkyl ethers of ethylene glycol and of diethylene glycol, i.e., mono methyl, mono ethyl and mono butyl ethers of ethylene glycol (ROCH 2CH 2OH) and mono methyl, mono ethyl and mono butyl ethers of diethylene glycol (ROCH 2CH 2OCH 2CH 2OH) with ethyl alcohol (C 2H 5OH) of different concentrations were studied in dilute solutions of benzene, dioxane and carbon tetrachloride at 35 °C. Permittivity ( ε′) and loss ( ε″) at 10.1 GHz, static dielectric constant ε o at 1 MHz and high frequency limiting dielectric constant ε ∞ = n D 2 at optical frequency of these molecules and their binary mixtures at different concentration were measured in dilute solutions of non-polar solvents. The average relaxation time τ o, relaxation times corresponding to overall molecular reorientation τ 1 and group rotations τ 2 were determined using Higasi's single frequency measurement equations for dilute solutions. The evaluated values of relaxation times and free energy of activation Δ F were used to explore the solvent effect on molecular dynamics of these polar binary systems in non-polar solvents. The excess inverse relaxation time and excess free energy of activation were determined to confirm the existence of hydrogen-bonded heterogeneous cooperative domains of the ethers and alcohol molecules at different concentration their binary mixtures in non-polar solvents. The dipole moment of the binary mixtures was evaluated using Higasi's and Guggenheim's equation for dilute solutions. The evaluated values of dipole moments and computed dipole moment values using a simple mixing equation of the polar molecules binary mixture were used to explore the effect of non-polar solvent environment on heterogeneous molecular interactions between ethers and alcohol molecules. The effect of number of carbon atoms in the molecular structure of these homologous series molecules was also considered for the interpretation of various evaluated dielectric parameters.

Fluid structure and molecular interaction of acetophenone derivatives

Dielectric constants of the binary mixtures of acetophenone,p-chloroaceto-phenone,p-methylacetophenone ando-hydroxyacetophenone in dilute solutions of benzene and 1,4-dioxane were measured at 303 K and at frequency 100 kHz. The low frequency molecular dynamics of acetophenone and its derivatives have been studied by evaluating the Kirkwood correlation factorg, molar polarizationP 2, excess correlation factor δg and excess free energy ΔG. The dipolar contribution to excess free energy of mixing arising from long-range electrostatic interaction and short-range interaction between identical molecules has been assessed separately. The presence of α- and β-multimers in the above systems was identified. The results have been used to interpret the fluid structure in such mixtures.