Palladium-catalyzed regioselective arylation of imidazo[1,2-a]pyrimidine

Imidazo[1,2-a]pyrimidine can be arylated at the 3-position with aryl bromides in the presence of base and a catalytic amount of palladium. This provides an efficient one-step synthesis of 3-arylimidazo[1,2-a]pyrimidines from the unsubstituted heterocycle. [reaction: see text]     

Selective Acetylation of Alcohols and Amines with Ethyl Acetate in the Presence of H<Subscript>6</Subscript>[PMo<Subscript>9</Subscript>V<Subscript>3</Subscript>O<Subscript>40</Subscript>] as the Catalyst

Summary. Acetylation of various alcohols and benzyl amine was tested in the presence of H₆[PMo₉V₃O₄₀], a mixed addenda heteropolyacid, in ethyl acetate under reflux condition. Phenols and anilines are not affected under the reaction conditions. Selective transestrification of alcohols can be achieved in the presence of phenol and aniline derivatives using this method.     

Exergetic and economic optimization of a solar-based cogeneration system applicable for desalination and power production

Journal of Thermal Analysis and Calorimetry - The selective drug delivery system could be an excellent alternative to fight cancer and pathogens, due to its minimized negative consequences....     

Rheology of interfacial layers

The response of interfacial layers to deformations in size and shape depends on their composition. The corresponding main mechanical quantities are elasticity and viscosity of dilation and shear, respectively. Hence, the interfacial rheology represents a kind of two-dimensional equivalent to the traditional bulk rheology. Due to growing interest in the quantitative understanding of foams and emulsions, more works are dedicated to studies on interfacial rheology. This overview presents the theoretical basis for traditional and recently developed experimental tools and discusses their application to different interfacial systems. While dilational rheology provides information on the composition of mixed interfacial layers, the shear rheology gives answers essentially on structures formed at an interface. The most frequently used methods at present are the oscillating drop and bubble tensiometry methods for dilational deformations and oscillating ring/bicone rheometers for shear deformations.     

Measurement of nonlinear refractive index of Ag and Au nano-particles using moiré technique

In this paper we have measured second order nonlinear refractive index of Ag and Au nano-particles using the moiré deflectometry with a CW He-Ne laser at wavelength of 632.8 nm. The main advantages of this technique are its extreme experimental simplicity and low sensitivity to external distribution in comparison with other interfrometric methods that need very stable experimental set-up. Because of self-focusing (or self-defocusing) that is due to intensity dependent refractive index, presence of sample in the moiré deflectometry set-up lead to rotation of moiré fringes. By moving the sample in set-up we have measured these rotation angles in different displacements from focus point of lens used in this set-up and then we have calculated the nonlinear refractive index of Ag and Au nano-particles using their values. Also we have obtained the sign of n₂ regard to the direction of rotations. Consequently by using the Mathematica software we have exhibited the suitable fitness of theoretical curve with experimental results.     

Heat-resistant and soluble fluorinated poly(amide imide)s based on non-coplanar ortho-linked diimide-dicarboxylic acid

A series of novel fluorinated heat-resistant poly(amide imide)s (PAIS) based on non-coplanar diimide-diacid monomer (DIDA) were synthesized and characterized. The poly(amide imide)s were obtained in high yields and possessed inherent viscosities in the range of 0.47-0.91 dL g⁻¹. All of the polymers were amorphous in nature, showed outstanding solubility and could be readily soluble in common organic solvents such as N,N-dimethylacetamide, N-methyl-2-pyrrolidinoned, dimethyl sulfoxide, N,N-dimethylformamide, pyridine and tetrahydrofuran. Glass transition temperatures were in the range of 221-263 °C, as determined by differential scanning calorimetry. Degradation temperatures for 10% weight loss occurred all above 520 °C and char yields was more than 50% at 700 °C in nitrogen atmosphere. Moreover, these PAIs possessed low refractive indexes (n = 1.58-1.59), birefringence (Δn = 0.008-0.013), and dielectric constants (? ≈ 2.5) due to the trifluoromethyl pendent groups and ortho-catenated aromatic rings that interrupt chain packing and increase free volume.     

Characterization methods for liquid interfacial layers

Liquid interfaces are met everywhere in our daily life. The corresponding interfacial properties and their modification play an important role in many modern technologies. Most prominent examples are all processes involved in the formation of foams and emulsions, as they are based on a fast creation of new surfaces, often of an immense extension. During the formation of an emulsion, for example, all freshly created and already existing interfaces are permanently subject to all types of deformation. This clearly entails the need of a quantitative knowledge on relevant dynamic interfacial properties and their changes under conditions pertinent to the technological processes. We report on the state of the art of interfacial layer characterization, including the determination of thermodynamic quantities as base line for a further quantitative analysis of the more important dynamic interfacial characteristics. Main focus of the presented work is on the experimental possibilities available at present to gain dynamic interfacial parameters, such as interfacial tensions, adsorbed amounts, interfacial composition, visco-elastic parameters, at shortest available surface ages and fastest possible interfacial perturbations. The experimental opportunities are presented along with examples for selected systems and theoretical models for a best data analysis. We also report on simulation results and concepts of necessary refinements and developments in this important field of interfacial dynamics.     

Second law of thermodynamics analysis for nanofluid turbulent flow inside a solar heater with the ribbed absorber plate

Journal of Thermal Analysis and Calorimetry - Employing rough surfaces and nanofluids in solar heater ducts are recognized as effective techniques to improve thermal performances of these devices....     

Atmospheric chemistry of 3-pentanol: kinetics, mechanisms, and products of Cl atom and OH radical initiated oxidation in the presence and absence of NOX

Smog chamber/FTIR techniques were used to study the atmospheric chemistry of 3-pentanol and determine rate constants of k(Cl+3-pentanol) = (2.03 +/- 0.23) x 10 (-10) and k(OH+3-pentanol) = (1.32 +/- 0.15) x 10 (-11) cm (3) molecule (-1) s (-1) in 700 Torr of N 2/O 2 diluent at 296 +/- 2 K. The primary products of the Cl atom initiated oxidation of 3-pentanol in the absence of NO were (with molar yields) 3-pentanone (26 +/- 2%), propionaldehyde (12 +/- 2%), acetaldehyde (13 +/- 2%) and formaldehyde (2 +/- 1%). The primary products of the Cl atom initiated oxidation of 3-pentanol in the presence of NO were (with molar yields) 3-pentanone (51 +/- 4%), propionaldehyde (39 +/- 2%), acetaldehyde (44 +/- 4%) and formaldehyde (4 +/- 1%). The primary products of the OH radical initiated oxidation of 3-pentanol in the presence of NO were (with molar yields) 3-pentanone (58 +/- 3%), propionaldehyde (28 +/- 2%), and acetaldehyde (37 +/- 2%). In all cases the product yields were independent of oxygen concentration over the partial pressure range 10-700 Torr. The reactions of Cl atoms and OH radicals with 3-pentanol proceed 26 +/- 2 and 58 +/- 3%, respectively, via attack on the 3-position to give an alpha-hydroxyalkyl radical, which reacts with O 2 to give 3-pentanone. The results are discussed with respect to the literature data and atmospheric chemistry of 3-pentanol.