Electrooxidation of carbo/thiocarbohydrazide and their hydrazone derivatives at a glassy carbon electrode

Electrochemical oxidation of thio/carbohydrazide and their hydrazone derivatives Benzaldehyde thiocarbohydrazone [BTCH] diacetylene thiocarbohydrazone [DATCH] have been studied in Brit-ton Robinson buffer in aqueous and nonaqueous media at a glassy carbon electrode. The effects of pH, sweep rate, concentration, temperature and surfactants have been studied. The complex bis (carbo/thiocabohydrazide) Zn(II) chloride was also subjected to voltammetric analysis in order to understand the reactivity both in free and metal bound states. The reaction conditions were optimized for the determination of above compounds in micrograms quantities by differential pulse voltammetry, analytical utility of this investigation is also highlighted.     

Preparation and properties of novel polyhydrazides

A new class of polyhydrazides having aromatic as well as aliphatic units has been synthesized by low-temperature solution polycondensation from equimolar amounts of diacid chloride and dihydrazides in HMPT as solvent. These polyhydrazides have poor solubilities and their intrisnsic viscosities ranged from 0.2 to 0.6 dl/g. X-ray diffractograms of these polyhydrazides show that the polymers having terephthalic acid dihydrazide unit were more crystalline and all the polymers have densities in the range of 1.2-1.8 g/cm³. Thermogravimetric analysis of these polyhydrazides showed initial weight losses commencing at 220–300°C in both air and nitrogen.     

Synthesis and properties of novel poly(N-oxyimide)s

Novel poly(N-oxyimide)s (PNOI) were synthesized by the room temperature polycondensation of N,N′-dihydroxypyromellitimide (I) with dichloro compounds in N,N-dimethylformamide (DMF) in the presence of triethylamine both as base as well as catalyst. The dichloro compounds used were 1,4-bis(chloromethyl)-2,5-dimethylbenzene (II), 1,5-bis(chloromethyl)-2,4-dimethylbenzene (III), 1,4-bis(chloromethyl)-2,5-dimethoxybenzene (IV) and 1,4-dichlorobut-2-yne (V). Polymer synthesis, characterization, and properties such as density, viscosity, solubility, crystallinity, and thermal stability were described. Two model compounds, viz. (i) MNOI-1 from N-hydroxyphthalimide and a dichloro compound (III), (ii) MNOI-2 from I and benzyl chloride were also synthesized to confirm the formation of polymers. The polymers thus obtained had high intrinsic viscosities in the range 1.09–1.18 dl/g. The thermal decomposition of the polymers started around 260°C with 20–25% decomposition and about 50% weight loss was observed at 400°C.     

Measuring the work of adhesion between a soft confined film and a flexible plate

We present a theoretical and experimental study of a method for the determination of the adhesion strength between a thin elastomeric film bonded to a rigid substrate and a flexible plate in a geometry common in the peel test. In particular, we characterize the work of adhesion in terms of the length of an equilibrium crack, generated by a spacer of known thickness wedged between the flexible plate and adhesive film, and the elastic and geometric properties of the film and the plate. We treat both the limit of perfect bonding and that of perfect slippage at the interface of the adhesive film and the flexible plate. A series of experiments allow us to verify the theory quantitatively and thus validate our method, which ought to be of value in many technological situations.     

Molecular and absolute crystal structure of pindolol-1-(1H-indol-4-yloxy)-3-[(1-methylethyl)amino]-2-propanol: A specific beta-adrenoreceptor antagonist with partial agonist activity

The crystal and molecular structure of pindolol, 1-(1H indol-4-yloxy)-3-[(1-methylethyl)amino]-2-propanol, has been determined by direct methods. Crystals are tetragonal, ,a=b=15.809(4),c=11.246(2) Å,Z=8,D _c=1.174 mg m^–3. The finalR-factor for 2271 reflections withI>2(I) is 0.038. Refinement by full-matrix least-squares on F² also enabled the absolute configuration of the structure to be established. The molecule is essentially planar, including much of the side-chain which is stabilized by the existence of two intramolecular H-bonds, between the ethyl oxygen and OH group, and between the OH and side-chain amide groups, respectively. The crystal structure is formed by three intermolecular hydrogen bonds including two side-chain-side-chain interactions, between ethyl oxygen to amide and OH to amide, and an interaction between the side-chain OH to indole NH.     

Redox polymerization of 2-hydroxyethyl methacrylate (HEMA). I. Influence of surfactants on polymerization kinetics

Oxidation of ferrous orthophenanthroline (FeP) by peroxydiphosphate (PP) in aqueous medium at pH 1 was followed spectrophotometrically. Kinetic analysis has shown that oxidation occurs via the formation of an intermediate complex between FeP and PP. Equi-librium and rate constants were calculated. Influence of surfactants on the oxidation of FeP by PP was also Investigated. The equilibrium constant for complex formation was found to be higher in the presence of surfactants. The enhanced complex formation has been attributed to the ionic interactions between the charged surfactant and the ionic species in the reaction medium. Polymerization of HEMA initiated by the redox system,FeP/PP, was carried out in aqueous medium, under the conditions of excess reductant over oxidant and excess oxidant over reductant. The polymerization followed different mech-anisms under these conditions; with excess oxidant, the growing polymer radicals underwent oxidative termination, while with excess reductant, primary radical termination was pre-ferred. The effect of surfactants on the aqueous polymerization of HEMA using the redox system FeP/PP was also investigated. In addition to the decrease in rate, the polymerization followed a different mechanism in the presence of surfactants, the growing radicals ter-minated by mutual interaction. © 1995 John Wiley & Sons, Inc.     

STUDIES ON THE INTERACTION OF EPOXY POLYMERS WITH HOMOPOLYUREAS

INTRODUCTION Epoxy resins are reactive polymers which when cured with a variety of chemicals lead to a host of useful thermosets. Since the epoxide is a strained ring, it readily undergoes addition and homopolymerization. The homopolymerization is a process catalysed by acids, bases, Lewis acids, t-amines as well as by inorganic salts.     

Oxidation of secondary alcohols byN-methylmorpholine-N-oxide (NMO) catalyzed by atrans-dioxo ruthenium(VI) complex or perruthenate complex: A kinetic study

Thetrans-dioxo ruthenium (VI) complex, [P(C₆H₅)₃C₆H₅CH₂]⁺[Ru(O)₂OAcCl₂] or tetrapropylammonium perruthenate catalyzes the oxidation of secondary alcohols to ketones byN-methylmorpholine-N-oxide (NMO). Kinetic studies showed the formation of a complex between catalyst and substrate (alcohol) as the first step in the mechanism.     

Redox polymerization of acrylonitrile. Kinetics of the reaction initiated by systems based on cyanoacetic acid/Mn(III) complexes in dimethylsulphoxide

The kinetics of polymerization of acrylonitrile initiated by the redox systems cyanoacetic acid/Mn(OAc)₃ and cyanoacetic acid/tris(benzoylacetonato)manganese(III) in dimethylsulphoxide as solvent have been investigated over the range 20–35°. The kinetics of oxidation are consistent with the formation of intermediate complexes between the reactants, followed by electron transfer. Manganous ions inhibit the reaction by competitive complexation. The primary radicals are very efficient as initiators of polymerization which is terminated by mutual interaction of macroradicals. Mechanisms have been proposed to explain the kinetics; rate and equilibrium constants have been evaluated.