P-xylene Solution Research Articles

Dielectric relaxation in o-chlorobenzaldehyde and o-methoxybenzaldehyde at microwave frequencies

Dielectric dispersion studies of o-chloro- and o-methoxy-benzaldehyde in dilute solutions of benzene and p-xylene have been carried out at spot frequencies in the x- and k-band microwave frequency region at 35 °C. The dispersion curves for these molecules in both the solvents have been resolved into two distinct Debye-type curves. The relaxation time and weight factor corresponding to overall rotation of the molecule and group rotation have been determined by extrapolation of the curves. The molecular dipole moment, the dipole moment corresponding to overall rotation of the molecule and of the group rotations have also been evaluated using the Higasi equation. The ratio of weight factors for the two relaxation processes obtained from dispersion loci is in good agreement with that obtained from dipole moment data for these molecules.

The dielectric relaxation mechanism and internal rotation in biphenyl derivatives

The dielectric relaxation mechanism of 2,2'- and 3,3'-dibromodiphenyl has been examined from measurements at different frequencies and temperatures. All dielectric measurement have been done on diluted solutions in p-xylene. A simple dielectric absorption band was observed in both cases. It was found that the Goulon-Rivail model provides a good description of the dielectric relaxation mechanism.

Morphology and mechanical properties of polyethylene gel films prepared from decalin and p-xylene solutions.

Films of ultrahigh molecular weight (3×106) polyethylene were prepared by gelation/crystallization from decalin and/or ρ-xylene solutions according to the method of Smith and Lemstra. The Young's moduli of the gel films prepared from decalin solution were higher than those prepared from xylene solution. This phenomenon was studied in terms of the relationship between the reduced viscosity of the solutions and the morphology of the resultant films. The morphology was estimated by wide angle X-ray diffraction, small angle X-ray scattering, and birefringence. It turned out that the Young's modulus is affected by the crystallinity and the crystallinity is also sensitive to the size or extension in space of polyethylene chains in the solution.

Kinetics of cobalt(III) reduction. 2. Reaction in p-xylene solution of p-toluic acid

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetics of cobalt(III) reduction. 2. Reaction in p-xylene solution of p-toluic acidJaroslav Novotny, Milan Hronec, and Jan IlavskyCite this: Ind. Eng. Chem. Res. 1989, 28, 10, 1471–1473Publication Date (Print):October 1, 1989Publication History Published online1 May 2002Published inissue 1 October 1989https://doi.org/10.1021/ie00094a006RIGHTS & PERMISSIONSArticle Views82Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (348 KB) Get e-Alerts Get e-Alerts

Synthesis and molecular structure of closo-3-(.eta.6-CH3C6H5)-3,1,2-FeC2B9H11 and closo-3-[.eta.6-1,4-(CH3)2C6H4]-3,1,2-FeC2B9H11

Abstract : The reaction of K(nido-7,8-C2B9H12) with ferric chloride and triethylamine in ether toluene or p-xylene solution afforded neutral mixed sandwich (arene) ferracarborane complexes closo-3-(n6-CH3C6H5)-3,1,2-FeC2B9H11 (1) or closo-3-(n6-1,4-(CH3)2C6H4)-3, 1,2-FeC2B9H11 (2), respectively. The molecular structures of the complexes have been determined fro single-crystal X-ray diffraction data. Both ferracarboranes adopt a closo geometry for the d6 MC2B9 icosahedra. The arene rings occupying the other coordination sites of Fe are planar and nearly parallel to the C2B3 plane of the carborane ligand. Complex 1 crystallized in the monoclinic space group P2/=1/c with a = 7.74552(&), b = 8.8974(9), c = 19.6596(20) A,B = 90.195(3), V = 1355 A and Z = 4. Complex 2 crystallized in the orthorhobic space group Pna21 with a = 12.862(3), b = 7.491(2), c = 15.002(3) A,V = 1445 A3 and Z = 4. Keywords: Arene, Metallacarborane, Complex, Ferracarborane, Arene Complex, Carboranes.

Longitudinal growth of polymer crystals from flowing solutions. X. Conditions for continuous growth on the rotor surface

AbstractUltrahigh strength polyethylene fibers can be generated by stress‐induced crystallization from a supercooled solution subjected to Couette flow, usually referred to as the “surface‐growth” process. Under appropriate conditions, continuous fiber production can be realized for a period as long as 19 days, whereas under other circumstances a rapid interruption of the growth process is met. The present investigation deals with the origin of fiber fracture during “surface growth.” The limiting values of process variables required to maintain continuous growth have been established. Interruption of the continuous growth can occur in three different ways: (1) formation of a closed fiberloop around the rotor; (2) limited crystal growth rate; (3) rapid crystallization, leading to depletion of the gel on the rotor surface. The gel layer is being formed by adsorption of long molecules on to the rotor surface and subsequent “reptation,” resulting in a dense entanglement network of these molecules. These factors determine the boundaries of the triangularly shaped domain for continuous growth in a graph of the two main variables, namely the takeup speed and the rotor speed. Furthermore, it was noticed that the introduction of a wedge‐shaped groove in the surface of the Couette rotor leads to a substantial reduction of failure. Continuous growth could be established in the temperature range from 103–125°C when p‐xylene was used as a solvent. For p‐xylene solutions at a crystallization temperature of 110°C and using a teflon rotor of 115 mm diameter, a maximum takeup speed and rotor speed were 16 and 180 mm/s, respectively. Basically the restrictions of the process appeared to be due to the limited rate of crystallization and rate of adsorption of polyethylene molecules on the surface of the rotor.

Chemiluminescence of organic peroxides. Thermal generation of an o-xylylene peroxide

Abstract : Thermolysis of 1,4-diphenyl-1,4-dioxa-2,3-benzopyrone (endoperoxide 1) in p-xylene solution generates chemiluminescence. Two intermediate products are formed from thermolysis of 1. The major product, trapped in 70% yield by added maleic anhydride, is 1,4-diphenyl-2,3-benzodioxin (o-xylylene peroxide 7). This peroxide becomes eventually o-dibenzoylbenzene 3 which is isolated from the reaction in 85% yield. The second intermediate is unidentified. It is formed in ca. 3% yield and apparently becomes eventually the other isolated product of the reaction phenyl-(o-benzoyl) benzoate (4). The chemiluminescence results from interaction of 7 with an added fluorescent activator or with the minor intermediate according to the chemically initiated electron-exchange luminescence (CIEEL) mechanism. (Author)

Target factor analysis of infrared spectra of multicomponent mixtures

The target factor analysis (t.f.a.) error criteria discussed earlier are applied to Fourier-transform infrared spectra in order to determine, without any prior knowledge of the experimental error, the number and identities of components in a series of related multicomponent mixtures. The t.f.a. method is also used for quantitative analysis and is compared to regression analysis, which force-fits the data and does not compensate for an impurity of small but measurable quantity. In addition, it is shown how an impurity in a single mixture can be detected, identified, and quantified. An actual experimental example is presented, using solutions of o-xylene, m-xylene, p-xylene, and ethylbenzene in cyclohexane, with chloroform as an impurity.

Isotropic and anisotropic scattering from polyethylene during crystallization

A light-scattering method for determining the optical anisotropy of large molecules is considered in detail. An application of the method is demonstrated to linear polyethylene while isothermally crystallizing in p-xylene solution. The polyethylene crystals formed are characterized as anisotropic thin discs having an optical anisotropy of 0.4–0.6.

Laser flash photolysis studies on excited singlet states of benzene, toluene, p-xylene, polystyrene, and poly-α-methylstyrene

Optical absorption spectra obtained in cyclohexane solutions of benzene, toluene, and p-xylene contain bands at 620 to 640 nm, assigned to S n← S 1 monomer transitions. With concentrated solutions, excimer absorption spectra nave been found. With the two polymers, absorption of (intramolecular) excimers has been detected only.

Angular correlations in linear copolymers from the compositional dependence of their dipole moments. V. Solvent–polymer interactions

Mean square effective dipole moments μ2e per structural unit have been determined at 298 K from a set of poly(4-chlorostyrene, 4-methylstyrene) copolymers, P (4CS,4MS), in p-xylene solutions containing 10 mole % copolymer. Coefficients which are related to local chain conformations have been evaluated from an expansion of the dipole moment ratio R (x) =μ2e(x)/μ2e(1) into a series of linearly independent functions of the mole fraction x of 4 CS units in the copolymer. The coefficient of the quadratic term, F2=1.01±0.06, obtained from these solutions is compared with the value 1.36±0.09, reported previously for the same set of copolymers in the undiluted state at 428 K. Extrapolations based on smoothed temperature coefficients which were derived from measurements in the range 360 to 440 K, yield a value F2=1.15±0.04 for the undiluted copolymers at 298 K. Uncertainties are standard deviations. It is argued that the copolymer method is relatively immune to the usual difficulties of determining dipole moments of molecules in condensed matter because it is framed in terms of ratios of experimental values of effective dipole moments. It is therefore suggested that the observed difference in values of F2 at 298 K reflects a difference in the local chain conformations resulting from the difference in the ’’solvent’’–polymer interactions in the two cases. Approximate values of the Kirkwood correlation factor g=μ2e/μ21 of P4CS, where μ1 is the moment of an equivalent freely orienting 4CS unit, are calculated from our results and compared with values obtained by others. This comparison supports the finding of Burshtein and Stepanova that g of P4CS increases toward unity as the thermodynamic quality of the solvents increase. We suggest that the copolymer method may provide a reliable means of separating a local component from the long range (excluded volume) dimensional changes that occur with changes of solvents.

Dielectric relaxation in 2-acetylnaphthalene and related compounds

The dielectric absorption of 2-acetylnaphthalene and 2- and 3-acetylphenanthrene has been studied in p-xylene solution at several microwave frequencies and in a polystyrene matrix at low frequencies. Acetyl group relaxation has been established from both sets of data. A clear separation of the dielectric absorption of the molecule and the group has been achieved for both 2- and 3-acetylphenanthrene in the matrix. The Eyring activation parameters have been established for acetyl relaxation in these molecules in the matrix. The free energy of activation values for group relaxation increase in the sequence acetophenone < 2-acetylphenanthrene < 3-acetylphenanthrene < 2-acetylnaphthalene. For the p-xylene solution data the weight factor for group relaxation, C2, is appreciably lower than the theoretical value, so that C2 < C1, bearing out the findings of Fong and Smyth for 2-acetylnaphthalene. In polystyrene matrices, the data for 2- and 3-acetylphenanthrene also indicated that C2 < C1. The enthalpy of activation for acetyl relaxation in 2- and 3-acetylphenanthrene is similar to that for acetophenone and 1,4-diacetylbenzene whereas that for 2-acetylnaphthalene would seem somewhat larger.

Lattice Defects in Normal Alcohol Crystals

Single crystals of normal octadecanol were grown by slow evaporation of p-xylene solution at room temperature. The crystals were of the γ-form structure (monoclinic) whose typical shape was a lozenge with major surfaces parallel to (001) surrounded by four {110} planes. X-ray diffraction topographic observation revealed that grown-in dislocations had <100>, <010>, <110> and <11̄0> Burgers vectors and lay on the (001) plane. Stress induced dislocations had the shortest Burgers vector <010>. The easiest glide plane was (001) plane. From inclusions, dislocation bands parallel to <010> were generated. They are considered to be arrays of prismatic dislocation loops induced by the prismatic punching mechanism.

Temperature and deuteration effects on the fluorescence of benzenoid solutions

Deuterium isotope substitution and temperature effects on the fluorescence of toluene and p-xylene solutions have been investigated. Values of fluorescence quantum yields were measured between −80° to 70°C for p-xylene, p-xylene d 10, toluene and toluene- d 8 and also fluorescence decay times at room temperature. The influence of several experimental factors on the fluorescence intensity at various temperatures was investigated and corrections were applied to obtain correct quantum yields. The results are compatible with an absence of a normal deuteration effect, and are independent of temperature, for both molecules, and show the existence of a non-radiative transition from the first excited single state to the ground state.

Longitudinal growth of polymer crystals from flowing solutions III. Polyethylene crystals in Couette flow

A detailed description is presented of several phenomena observed during the longitudinal growth of fibrillar polyethylene crystals from xylene solutions subjected to Couette flow. The rate at which the extended chain seed crystals grow longitudinally in this flow field could be established by measuring the increment in length of the macrofiber in a given period of time and also by finding the take-up speed under steady-state conditions which is equal to the growth rate. Continuous macrofibers of polyethylene with lengths of several hundred meters could be produced by this technique. The growth rate of the seed crystals anchored at a distance of approximately i mm from the surface of the rotating inner cylinder was found to increase linearly with the rotor speed, and these growth rate data agreed remarkably well with those values obtained in Poiseuille flow at corresponding local velocity gradients. Scanning electron micrographs reveal that these macrofibers, having diameter in the micron range, are composed of bundles of elementary fibrils of the Shish-Kebab type. It is believed that these Shish-Kebab backbones grow simultaneously by the action of the local flow field. The diameters of the macrofibers increase with the rotor speed as a result of branching of the backbone tips. The growth of seed crystals pushed against the rotor surface is considerably faster than the growth of seeds, around which the polymer solution flows freely. This fast growth is promoted by the roughness of the rotor surface and by the presence of methyl groups on the glass rotor surface introduced by silanization. These experimental observations suggest that the active element in this fast “surface-growth” is a layer of adsorbed polyethylene molecules on the rotor surface. By this surface-growth technique, continuous fibrillar crystallization appeared to be possible at a temperature of even 120.5 °C, which is well above the thermodynamic equilibrium temperature in a dilute p-xylene solution, and the longitudinal growth rate of the polyethylene macrofiber at this high temperature was still 6 cm/min.

Dielektrische Relaxation und Elektronenspinrelaxation von Eisen(III)acetylacetonat in verdünnter Lösung/ Dielectric Relaxation and Electron Spin Relaxation of Ferric Acetylacetonate in Dilute Solutions

Abstract The dielectric loss and electron spin resonance linewidth of ferric acetylacetonate have been measured in dilute solutions of benzene, m-and p-xylene, mesitylene and carbon tetrachloride. Permittivity measurements were made at 10 frequencies in the microwave region (1.2 m to 1 mm wave-length), ESR measurement at 2 frequencies (X and Q band). The permittivity results show a broad non-Debye pattern, yielding a mean correlation time of about 4 ps. The ESR results yield a mean correlation time of about 3 ps. The parallelism between the results obtained by both methods is discussed in view of a common relaxation process, which is the transient deformation of the chelate system resulting from stochastic induction by neighbouring solvent molecules.

Dipole moment studies of lactams

The electric moments of a series of substituted N-phenyl-β-lactams were measured in p-xylene solution. This study gives evidence that the dihedral angle between the N-phenyl ring and the β-lactam ring of the ortho-bromo and orthofluoro derivatives is 52° and 42° with the halogen lying on the side farthest from the keto group. Ultraviolet data appear to substantiate this conclusion. Dipole data indicate that the N-phenyl-3-azido-4- p-nitrophenyl-β-lactam compound has a cis configuration with respect to the azido and p-nitrophenyl groups. The moments and conformations of some γ-lactams and δ-lactams are also discussed.

Dielectric Studies. Part XXXV. Relaxation Studies of Benzaldehyde and Fourpara-Substituted Aideliydes

The dielectric absorption has been determined for benzaldehyde, p-fluoro-, p-chloro-, p-bromo-, and p-nitro-benzaldehyde in p-xylene solution at mainly five or six frequencies in the 6.70 to 70.1 GHz region. For all three p-halo-substituents the mean relaxation time values indicate that some mechanism faster than molecular relaxation occurs whereas none was apparent in benzaldehyde itself. A detailed study has been made of p-chlorobenzaldehyde in p-xylene solution at five temperatures, and the data have been analyzed into contributions from a molecular relaxation process and a shorter relaxation time τ2. In the p-xylene solutions of benzaldehyde the relaxation data indicate weak intermolecular hydrogen bonding between the solute and the solvent which is probably of the type [Formula: see text]

Dipole moments of silver perchlorate in benzene, p-xylene and mesitylene

The dielectric constants and refractions of solutions of benzene, p-xylene and mesitylene containing silver perchlorate have been measured. For very low concentrations in benzene, a dipole moment of 10.7 D was confirmed but in more concentrated solutions a value of 4.7 D was obtained. For p-xylene and mesitylene only one value was obtained: 2.7 D in the case of p-xylene solutions and 4.3 D for mesitylene solutions. This behaviour is discussed in terms of ion pair association and donor-acceptor interactions taking place in such systems between the aromatic species and the silver ion.

Thermodynamic and Conformational Properties of Styrene–Methyl Methacrylate Block Copolymers in Dilute Solution. V. Light-Scattering Analysis of Conformational Anomalies in p-Xylene Solution

Thermodynamic and Conformational Properties of Styrene–Methyl Methacrylate Block Copolymers in Dilute Solution. V. Light-Scattering Analysis of Conformational Anomalies in p -Xylene Solution