Nano-TiO_2:An eco-friendly alternative for the synthesis of quinoxalines

Nano-TiO₂ as an eco-friendly and efficient nanocatalyst was applied for quinoxaline preparation with improved yield.In this protocol,diketones and 1,2-diamines were condensed in the presence of catalyst at room temperature.     

Determination of the effective atomic and mass numbers for mixture and compound materials in high energy photon interactions

In consideration the radiological properties of materials and studying the scattering processes in atomic and nuclear physics, the effective atomic and mass numbers is widely employed. These numbers have been calculated for any mixed or composite materials in interaction with high energy photons (Linac in radiation therapy). A pair equation in terms of these numbers is obtained. The first equation has been derived from the conservation of mass energy law and the second by minimizing the binding energy from the semiempirical mass formula (Myers and Swiatecki formula) that gives a relation between atomic and mass numbers for stable nuclei approximately. By these equations one can obtain the effective atomic and mass numbers for any compound or mixed materials uniquely. These numbers are calculated for some materials and compared with the other studies.     

A convenient synthesis of bis(indolyl)alkanes under ultra sonic irradiation using silica-supported Preyssler nano particles

Bis(indolyl)alkanes have been synthesised in excellent yields in the presence of catalytic amount of silica-supported Preyssler nano particles as green, reusable and efficient catalyst under ultra sonic irradiation.     

An enaminone-directed benzannulation/macrocyclization approach to cyclophane ring systems

A straightforward and modular preparative approach to 1,3,5-triaroylbenzene-based functionalized cyclophane ring systems has been developed. The key cyclophane-forming macrocyclization reaction was accomplished during the course of a regioselective cross-benzannulation between bis(aryl ethynyl) ketone and enaminone reactants. Macrocyclic products with ring sizes ranging from 18- to 22-membered were successfully constructed. The composition of the tether connecting the two aryl ethynyl ketone fragments can be easily varied; consequently, this method is suitable for construction of a diverse range of structurally distinct cyclophane products. To illustrate this feature, cyclophanes possessing xylyl, alkyl, di(ethylene triamine), and di(ethylene oxy) bridging units were synthesized in isolated yields of 11-46%. Three new cyclophanes (calixarene-like macrocyles 8 and 9, as well as crownophane 18) were structurally characterized by X-ray diffractometry.     

Viscoelastic characterization of compacted pharmaceutical excipient materials by analysis of frequency-dependent mechanical relaxation processes

A newly developed method for determining the frequency-dependent complex Young's modulus was employed to analyze the mechanical response of compacted microcrystalline cellulose, sorbitol, ethyl cellulose and starch for frequencies up to 20 kHz. A Debye-like relaxation was observed in all the studied pharmaceutical excipient materials and a comparison with corresponding dielectric spectroscopy data was made. The location in frequency of the relaxation peak was shown to correlate to the measured tensile strength of the tablets, and the relaxation was interpreted as the vibrational response of the interparticle hydrogen and van der Waals bindings in the tablets. Further, the measured relaxation strength, holding information about the energy loss involved in the relaxation processes, showed that the weakest material in terms of tensile strength, starch, is the material among the four tested ones that is able to absorb the most energy within its structure when exposed to external perturbations inducing vibrations in the studied frequency range. The results indicate that mechanical relaxation analysis performed over relatively broad frequency ranges should be useful for predicting material properties of importance for the functionality of a material in applications such as, e.g., drug delivery, drug storage and handling, and also for clarifying the origin of hitherto unexplained molecular processes.     

The selective aerobic oxidation of methylaromatics to benzaldehydes using a unique combination of two heterogeneous catalysts

A unique combination of a supported cobalt complex and the first example of supported NHPI in acetic acid gives a surprisingly stable heterogeneous catalytic system for the selective aerobic oxidation of methylaromatics to benzaldehydes at atmospheric pressure.     

Sensitive Kinetic-Spectrophotometric Determination of Trace Amounts of Periodate Ion

A simple, precise, sensitive and accurate method was developed for rapid determination of trace quantities of periodate. The method is based on the accelerating effect of periodate on the reaction of bromate and hydrochloric acid in the presence of hydrazine. The decolorization of methyl orange with the reaction products was used to monitor the reaction spectrophotometrically at 525 nm. Periodate could be determined in the concentration ranges of 0.02–1.5 g/mL. The relative standard deviation for ten replicate determinations of 0.3 g/mL of periodate was 1.12%. The method was applied to the determination of periodate in water samples and indirect determination of ethylene glycol in gasoline and glycerol in vegetable oil via Malaprade reaction with satisfactory results.     

A PVC-based 1,8-diaminonaphthalen electrode for selective determination of vanadyl ion

A PVC membrane vanadyl (VO²⁺) ion-selective electrode was constructed using 1,8-diaminonaphthalen (DAN) as a neutral carrier. The electrode shows good Nernstian response for VO²⁺ ions over a wide concentration range (1.0×10⁻¹-1.0×10⁻⁵ M). The optimum composition of the membrane was 55 wt.% poly(vinylchloride), 35 wt.% 2-nitrophenyl octyl ether (NPOE), 5 wt.% ionophore, and 5 wt.% potassium tetrakis(p-chlorophenyl)borate (KTpClPB). It has relatively fast response time and can be used at least for 5 weeks without any considerable divergence in potentials. The proposed electrode revealed relatively good selectivity for VO²⁺ over wide variety of other metal ions. The electrode was used for the potentiometric titration of VO²⁺ ions with EDTA.