Direct synthesis of Zn(II) and Cu(II) coordination polymers based on 4,4′-bipyridine and 1,10-phenanthroline and evaluating their effects as catalyst on ammonium perchlorate thermal decomposition

Journal of Thermal Analysis and Calorimetry - Two coordination polymers (CPs) material, [Zn(μ-Cl)2(μ-bpy)]∞ (bpy?=?4,4′-bipyridine) and [Cu(bpy)(phen)(ClO4)2]n...     

Turbulent heat transfer in tubular heat exchangers with twisted tape

Journal of Thermal Analysis and Calorimetry - Enhancing heat transfer in heat exchangers has gained attention of researchers for many years because of reduction in costs of generating heat...     

Characterization,thermal degradation kinetics,and morphological properties of a graphene oxide/poly (vinyl alcohol)/starch nanocomposite

Journal of Thermal Analysis and Calorimetry - In this study, we synthesized a biodegradable nanocomposite containing starch, polyvinyl alcohol (PVA), and graphene oxide (GO). The non-isothermal...     

Multiple 1,2,3-thiadiazoles

A series of compounds 3a-d,i-n with two or three 1,2,3-thiadiazole rings, useful for photocrosslinking processes, was prepared from the di- or triketones 1a-d,i-n via the corresponding hydrazones 2a-d,i-n by applying the Hurd-Mori method. A special synthetic sequence, 1e, 2e, 3e, 3f/3g , was elaborated for the olefinic system 3h.     

Analysis of enkephalins, beta-endorphins and small peptides in their sequences by highly sensitive high-performance liquid chromatography with electrochemical detection: implications in opioid peptide metabolism

Sensitivity in the 10-100 pg range for enkephalins, beta-endorphin, tyrosine (T), 12 tyrosylglycine (T-G) and tyrosylglycylglycine (T-G-G) was attained by using a high-performance liquid chromatographic (HPLC) method with electrochemical detection which is at least 100 times more sensitive than HPLC with UV detection. The chromatographic conditions on a reversed-phase C18 silica column were 50 mM sodium phosphate buffer (pH 2.1) (A) in acetonitrile-methanol (1:1) (B), isocratic mixture, flow-rate 0.6-1 ml/min, UV detection at 205 nm, electrochemical oxidation potential + 1.25 V. The separation of T, T-G and T-G-G was obtained by using 10% B while the separation of the pentapeptide, enkephalins required 40% B. Separation of enkephalins from beta-endorphin was attained at a shorter retention times did not exceed 15 min. This method can be used to determine tissue levels and pharmacodynamics of enkephalins and beta-endorphin. A highly specific measurement of the different enzymes involved in the metabolism of enkephalin has been achieved.     

Metal-Assisted Oxidative Cyclization of Arylamidrazones I. Synthesis of 3-Acetyl-1,4-dihydro-1-phenyl-1,2,4-benzotriazine

Summary. In the presence of RuCl₃, N-phenylamidrazone underwent oxidative cyclization into 1,4-dihydro-1-phenyl-1,2,4-benzotriazine, the structure of which is established by spectral and X-ray diffraction data.     

Electrochemical Behavior and Determination of Hyoscine‐N‐Butylbromide from Pharmaceutical Preparations

The electrooxidation of hyoscine N‐butylbromide (HBB) was investigated by rotating disk electrode voltammetry, cyclic voltammetry and controlled potential coulometry in 0.1 M HNO₃ and in 0.1 M tetrabutylammonium perchlorate (TBAP) solutions of acetonitrile at a platinum (Pt) electrode. Based on the results obtained, it is suggested that a bromide ion of HBB was oxidized in one reversible step in aqueous solutions and in two reversible steps in acetonitrile. A differential pulse voltammetric (DPV) method at a Pt electrode was developed for the determination of HBB in the concentration range of 1.0 × 10^?6‐1.0 × 10^?3 M. The procedure was applied to the determination of HBB in its formulations as well as its recovery from blood serum and urine samples.     

Potassium peroxydisulfate as an efficient oxidizing agent for conversion of ethyl 3,4-dihydropyrimidin-2(1H)-one-5-carboxylates to their corresponding ethyl pyrimidin-2(1H)-one-5-carboxylates

Various ethyl 3,4-dihydropyrimidin-2(1H)-one-5-carboxylates were oxidized to their corresponding ethyl pyrimidin-2(1H)- one-5-carboxylates by potassium peroxydisulfate in refluxing aqueous acetonitrile. The products were obtained in good to excellent yields. The effect of the nature of 4-substituent and also the nature of solvent play an important role on the rate of oxidation.