Mechanism of oxidation of diazepam by 1-chlorobenzotriazole in acidic medium. A kinetic approach

The kinetics of oxidation of diazepam (DZ) by 1-chlorobenzotriazole (CBT) has been studied in HClO₄ medium in the temperature range of 293–323 K. The reactions followed a first order dependence on [CBT], fractional order each in [H⁺] and [DZ]. Activation parameters were evaluated. A negative entropy of activation indicated the involvement of a rigid complex in the activated state. Variation of reaction rate with dielectric constant and the ionic strength are consistent with a mechanism involving the decomposition of a dipole in the rate-determining step. Rate equation is derived to account for the observed kinetic data and the proposed reaction mechanism.     

Hydromagnetic flow in a rotating channel

The steady flow in a parallel plate channel rotating with an angular velocity Ω and subjected to a constant transverse magnetic field is analysed. An exact solution of the governing equations is obtained. The solution in the dimensionless form contains two parameters: the Hartmann number, M ², and K ² which is the reciprocal of the Ekman number. The effects of these parameters on the velocity and magnetic field distributions are studied. For large values of the parameters, there arise thin boundary layers on the walls of the channel.     

A 1D Cu(II) coordination polymer exhibiting ferromagnetic interactions and a mononuclear Cu(II) complex of substituted pyrazole carboxylic acids: Synthesis, characterization and crystal structure

Reaction of 2 equiv. amount of copper(II) nitrate hexahydrate with 1 equiv. of 5-methyl-1-pyridin-2-yl-1H-pyrazole-3-carboxylic acid (PyPzCA) in presence of triethyl amine base afforded a 1D coordination polymeric compound [Cu₂(PyPzCA)₂(H₂O)₃(NO₃)]NO₃·H₂O (1). Whereas, the same reaction when repeated with 1-(4,6-dimethyl-pyrimidin-2-yl)-5-methyl-1H-pyrazole-3-carboxylic acid (PymPzCA) instead of PyPzCA, a mononuclear compound [Cu(PymPzCA)]·2H₂O·NEt₃ (2) is formed. Both the complexes are crystallographically characterized. In 1, both the copper atoms (Cu1 and Cu2) have distorted square pyramidal geometry with N₂O₃ chromophore while, in 2, the central copper atom has a distorted trigonal bipyramidal geometry with N₄O chromophore. Complex 1, is a 1D coordination polymer where the metal centers being far apart and are involved in a weak ferromagnetic interaction which is quite unexpected.     

High Energy Density Supercapacitors: An Overview of Efficient Electrode Materials,Electrolytes, Design,and Fabrication

Supercapacitors (SCs) are potentially trustworthy energy storage devices, therefore getting huge attention from researchers. However, due to limited capacitance and low energy density, there is still scope for improvement. The race to develop novel methods for enhancing their electrochemical characteristics is still going strong, where the goal of improving their energy density to match that of batteries by increasing their specific capacitance and raising their working voltage while maintaining high power capability and cutting the cost of production. In this light, this paper offers a succinct summary of current developments and fresh insights into the construction of SCs with high energy density which might help new researchers in the field of supercapacitor research. From electrolytes, electrodes, and device modification perspectives, novel applicable methodologies were emphasized and explored. When compared to conventional SCs, the special combination of electrode material/composites and electrolytes along with their fabrication design considerably enhances the electrochemical performance and energy density of the SCs. Emphasis is placed on the dynamic and mechanical variables connected to SCs′ energy storage process. To point the way toward a positive future for the design of high-energy SCs, the potential and difficulties are finally highlighted. Further, we explore a few important topics for enhancing the energy densities of supercapacitors, as well as some links between major impacting factors. The review also covers the obstacles and prospects in this fascinating subject. This gives a fundamental understanding of supercapacitors as well as a crucial design principle for the next generation of improved supercapacitors being developed for commercial and consumer use.     

A study of the crystallization kinetics of PVF2 by DSC and dilatometry

Poly(vinylidene fluoride) was crystallized isothermally from the melt at several temperatures. Crystallization rates have been measured using dilatometry and differential scanning calorimetry. The results were analysed in terms of the Avrami equation. The different methods yielded similar values for the kinetic parameters. The surface free energy of the lamellar crystallites has been determined.     

Higher surface energy of free nanoparticles

We present an accurate online method for the study of size-dependent evaporation of free nanoparticles allowing us to detect a size change of 0.1 nm. This method is applied to Ag nanoparticles. The linear relation between the onset temperature of evaporation and the inverse of the particle size verifies the Kelvin effect and predicts a surface energy of 7.2 J/m(2) for free Ag nanoparticles. The surface energy of nanoparticles is significantly higher as compared to that of the bulk and is essential for processes such as melting, coalescence, evaporation, growth, etc., of nanoparticles.     

Reactions of coordinated ligands,Part III(1). Kinetics of lodination of malonate and pyruvate in malonato(pentaammine)-cobalt(III), malonato-bis-(ethylenediamine)cobalt(III) and pyruvato(pentaammine)cobalt(III) ions

Summary The kinetics of iodination of malonate and pyruvate in the title complexes are reported at 35.0 °C and I=0.3 M. The reaction is first order in substrate and zeroth order in [I₂]. This result is commensurate with rate determining enolisation of the active methylene and methyl groups of the malonate and pyruvate respectively. The reaction is catalysed by H₂O, OH^– and by the buffer anions used. The rate data suggest that the malonate methylene group in the [Co(en)₂-O₂CCH₂CO₂]²⁺ chelate is considerably more active towards electrophilic substitution than is the case in [Co(NH₃)₅O₂CCH₂CO₂]²⁺.