Preparation and spectroscopic properties of 2'''',5''''-dideoxynucleosidylcobalamins

Two new coenzyme B12 analogues, 2',5'-dideoxycytidylcobalamin (2a) and 2',5'-dide-oxyuridinylcobalamin (2b), and two others, 2',5'-dideoxyadenosylcobalamin (2c), and 5'-deoxy-thymidylcobalamin (2d) were prepared by an improved method. All the four analogues were investigated by UV-vis and 2D 1H NMR spectroscopy. The comparisons and discussion about their spectroscopic properties were done.     

Study of some volumetric and refractive properties of {PEG 300 (1) + ethanol (2)} mixtures at several temperatures

Molar volumes and excess molar volumes were investigated from measured density values for {PEG 300 (1) + ethanol (2)} binary mixtures at temperatures from 278.15 to 313.15 K. Both systems exhibit negative excess volumes probably due to increased interactions like hydrogen bonding and/or large differences in molar volumes of the components. Volume thermal expansion coefficients were also calculated for both binary mixtures and pure solvents. Refractive indices were also determined for all these non-aqueous mixtures and neat solvents at all temperatures. Furthermore, the Jouyban–Acree model was used for density, molar volume and refractive index correlations of the studied mixtures at different temperatures. The mean relative deviations between experimental and back-calculated density, molar volume and refractive index data were 0.07%, 0.99% and 0.01%, respectively.     

Physico-chemical,acoustic and excess properties of glycylglycine–MnCl2 in aqueous ethanol mixtures at different temperatures

Volumetric, acoustic, refractometric, excess and deviation properties of glycylglycine–MnCl₂ in aqueous ethanol mixtures have been reported at T = (288.15 to 318.15) K. Redlich–Kister equation was used to fit the derivate properties. The experimental data of the constituent binaries were analyzed to discuss the nature and strengths of intermolecular interactions. The interdependence of L_f and u has been evolved from Eyring and Kincaid model. The variations in specific acoustic impedance revealed that hydrogen bonding was predominant in the studied binary mixtures. Solvation number indicated structure-breaking tendency of the solute and weakening of local solvent structure.     

Electrical conductivity properties of some O-substituted arylazo — Barbiturate complexes at different temperatures

Electrical conductivity properties of someo-substituted arylazo-barbiturate complexes at different temperatures are studied. The _o, E andE _g values are determined. The copper complexes derived from –H, –CH₃ and –OCH₃ substituted organic compounds are with semiconducting properties at low temperatures and insulator at high temperatures. All the carboxy and the cobalt and the the nitro complexes, and nickel-methyl complexes are of semiconducting behaviour. The data are explained in the light of extrensic and lattice vibrations and the width of the forbidden energy gap properties.

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Zusammenfassung Bei verschiedenen Temperaturen wurden die elektrischen Leitfähigkeitseigenschaften einiger o-substituierter Arylazobarbiturat-Komplexe untersucht und Werte für _o,E undE _g ermittelt. Die durch H-, CH₃- und OCH₃-Substitution der organischen Verbindungen erhaltenen Kupferkomplexe zeigen bei niedrigen Temperaturen Halbleiter- und bei hohen Temperaturen Isolatoreigenschaften. Alle Carboxy- und Nitrokomplexe sowie die Kobalt- und die Nickel-Methyl-Komplexe zeigen Halbleiterverhalten. Die Ergebnisse werden angesichts von Störstellen- und Gitterschwingungen und der Breite der verbotenen Energiezone erklärt.

     

Synthesis, spectroscopic properties, and tautomerism of mono-meso-substituted octamethylporphyrins

The synthesis spectroscopic properties and tautomerism of four novel mono-meso substituted(R)-octamethylporphyrins (R=o-hydroxybenzyl, p-aminobenzyl, 4-pyridinyl, and ferro-cenyl) were investigated. It was found that the porphyrins 2, 3 could be directly prepared in good yields via the coupling reaction of salicylaldehyde and p-aminobenzyl aldehyde with octamethyl-l',8'-dideoxy-ac-biladiene dihydrobromide, respectively. The free energy of activation (G) of the tautomerism of the porphyrins was calculated and interpreted in terms of electronic and steric nature. In contrast with 2-substituted-5,10,15,20-tetraphenylporphyrins, the substituents in meso position do not change the relative amount of two tautomers a and 6.     

Effect of supercritical carbon dioxide treatment on structure and mechanical properties of β-nucleated polypropylene processed at different temperatures

Polypropylene (PP) was compounded with β-nucleating agent and injection-molded at 180 °C or 220 °C. The samples were subsequently treated by supercritical carbon dioxide (scCO₂) at different temperatures. Results show that processing temperature and scCO₂ treatment could strongly influence the tensile and impact properties of β-nucleated PP. In particular, the sample processed at 220 °C and treated at 120 °C exhibit much enhanced impact strength (4.8 times that of its untreated counterpart). FTIR, WAXD, SEM and DMA were performed to explore the effects of processing temperature and scCO₂ treatment on structure of the samples. Deformation-induced plastic flow and micro-voids were also evaluated to construct structure-property relations. It was found that the influence of processing temperature on mechanical properties is mainly associated with the β-form content and β-crystalline morphology, while the structural changes in the crystalline lamellar scale may be responsible for the toughening effect of scCO₂ treatment.     

Solubility of minoxidil in binary mixture of ethanol + water at various temperatures

ABSTRACT

The solubility of minoxidil in the aqueous binary mixtures of ethanol at different temperature are investigated and the obtained solubility data are fitted by using some cosolvency models including van’t Hoff equation, Yalkowsky model, Jouyban–Acree model and Jouyban–Acree–van’t Hoff model. The mean relative deviations (MRD%) are used to illustrate the models performance. Moreover, the apparent entropy, enthalpy, and Gibbs free energy of minoxidil dissolution process in the investigated solvent mixtures are computed using van’t Hoff and Gibbs equations. Finally, by means of the inverse Kirkwood–Buff integrals preferential solvation of minoxidil by water is observed in water-rich and ethanol-rich mixtures.     

Role of cationic moiety in phosphate fertilizers’ molecules on their solution behavior in terms of volumetric and acoustic parameters at different temperatures and atmospheric pressure

Ultrasonic parameters are very useful tools used to study the physic-chemical behavior and molecular interactions of various liquid mixtures. More than 50% problems of irrigated areas are associated with cultivated land and they frequently occur due to salinity. Application of fertilizers into agricultural land could be a remedy for soil salinity by providing essential nutrients to plants. In this research paper, ultrasonic and volumetric properties of phosphate based fertilizers of different molecular compositions at different temperatures have been studied. This is experimental based work; this knowledge can be employed in formulation of fertilizers according to the nature of their application which could enhance fertilizer’s activity either in terms of nutrients development or to control the salinity of soil. Results obtained from calculated ultrasonic and volumetric parameters indicated presence of strong interactions in aqueous fertilizer solutions which depends upon nature of molecules. Among presently studied phosphate fertilizers i.e. triple superphosphate, nitrophosphate and diammonium phosphate, maximum molecular interactions were observed in aqueous triple super phosphate solutions due to the presence of highly charged cationic specie i.e. calcium ions, which can also be used to control the salinity of soil using electrostatic interactions among saline salts and charged cationic species.     

Thermodynamic properties of N,N-dimethylformamide + water

The excess viscosities, η^E, and excess energy of activation (ΔΕ_η)^Ε of dynamic viscosity have been investigated by using dynamic viscosity measurements for N,N-dimethylformamide + water (DMFW) mixtures over the entire range of mole fractions at five different temperatures. The results were also fitted with the Redlich–Kister equation. This system exhibited very large positive values of η^E and (ΔΕ_η)^Ε due to the increased dipole–dipole interactions and correlation length between unlike molecules. The activation parameters ΔΗ_σ and ΔS_σ have been also calculated, and they show that the critical region has an important effect on the dynamic viscosity properties. The results obtained are discussed from the viewpoint of the existence of interactions between the components.     

Conformational and spectroscopic properties of π-extended, bipyrrole-fused rubyrin and sapphyrin derivatives

Two new expanded porphyrins, naphthorubyrin and naphthosapphyrin, were synthesized. The π-extended rubyrin was isolated and structurally characterized in its monoprotonated form. The sapphyrin congener undergoes pyrrole inversion as a function of the protonation state. These conformational effects are reflected in the spectroscopic features, including the excited singlet state lifetimes.     

The reduced Redlich–Kister equations for correlating volumetric and viscometric properties of N,N-dimethylacetamide + dimethylformamide binary mixtures at temperatures from 298.15 to 318.15 K

Excess molar volumes and viscosity deviations in N,N-dimethylacetamide?+?dimethylformamide binary mixtures at 298.15, 308.15 and 318.15?K were calculated from experimental density and viscosity data presented in the previous work. Here these experimental values were used to test the applicability of the correlative reduced Redlich–Kister equation and the recently proposed Herráez equation. Their correlation ability at different temperatures, and the use of different number of parameters, is discussed for the case of limited experimental data. These relative functions are important to reduce the effect of temperature and, consequently, to reveal the effects of different types of interactions. Limiting excess partial molar volumes at infinite dilution were deduced from different methods, parameters of molar Gibbs energy of activation of viscous flow against compositions were investigated. The results of these observations have been interpreted in terms of structural effects of the solvents. ¹H-NMR studies of these mixtures are also reported.     

Viscosity Arrhenius activation energy and derived partial molar properties in of N,N-dimethylacetamide + 2-ethoxyethanol binary mixtures at temperatures from 298.15 K to 318.15 K.

Calculation of excess properties in N,N-dimethylacetamide + 2-ethoxyethanol binary mixtures at (298.15, 308.15 and 318.15) K from experimental density, viscosity and sound velocity values were presented in previous work. Applications of these experimental values to test different correlation equations as well as their corresponding relative functions were also reported. Considering the quasi-equality between the Arrhenius activation energy Ea and the enthalpy of activation of viscous flow ?H*, here we can define partial molar activation energy Ea1 and Ea2 for N,N-dimethylacetamide and 2-ethoxyethanol, respectively, along with their individual contribution separately. Correlation between the two Arrhenius parameters of viscosity in all the domains of composition shows the existence of two main distinct behaviours separated by a stabilised structure in a short range of mole fraction in N,N-dimethylacetamide from 0.14 to 0.45. We add that correlation reveals interesting Arrhenius temperature, which is closely related to the vaporisation temperature in the liquid vapour equilibrium.     

Migration of perfluorinated compounds from paperbag to Tenax® and lyophilised milk at different temperatures

ABSTRACT

Migration tests of perfluoroalkyl substances (PFASs) from a grease-proof paperbag used for packaging of pet food have been carried out. No migration of perfluorocaboxylic acids (PFCAs), from PFBA to PFTeDA, to the simulant Tenax® was found after 10 days at 40°C. However, the increase of temperature in the range 80–160°C gave rise to the migration of the PFCAs. Finally, the migration to real foods such as lyophilised whole and low-fat milk samples at 80 and 120°C was studied. The results indicate that the migration percentages of the PFCASs into food samples are much higher than those obtained into Tenax®.