Chemical aspects of the hypergolic preignition reactions of some hybrid hypergols

A new class of solid compounds, viz., bisthiocarbonohydrazones and thiosemicarbazones, have been found to be hypergolic with fuming nitric acid. The observed ignition delays of these hypergols have been compared with those of the monothiocarbonohydrazones-nitric acid systems and explained in terms of the chemical reactions-neutralization, oxidation, and nitration-occurring in the preignition stage. p-Nitrobenzoic acid, benzoic acid, benzaldehyde, sulfur trioxide, nitrogen dioxide, and nitrogen have been isolated as preignition reaction intermediates in the mono- and bisbenzaldehydethiocarbonohydrazone-nitric acid systems. A scheme of reactions occurring in the preignition stage is proposed based on the formation of these products.

Kinetics Of The Aminolysis Reactions Of Chlorocyclotriphosphazenes-Changeover From A Sn2(P) To A Sn1(P) Mechanism

A change-over from SN2(P) to SN1(P) mechanism is established for the chlorine replacement reactions of halogenocyclophosphazenes; this mechanistic change-over helps in rationalising the diverse findings reported for this class of reactions.

Fractional power dependence of rate on activation energy for reactions with very low internal barriers

The dynamics of reactions with low internal barriers are studied both analytically and numerically for two different models. Exact expressions for the average rate,kI, are obtained by solving the associated first passage time problems. Both the average rate constant, kI, and the numerically calculated long-time rate constant, kL, show a fractional power law dependence on the barrier height for very low barriers. The crossover of the reaction dynamics from low to high barrier is investigated.

A comparative study of the photochemical hydrogen-abstraction reactions of a ketone and a thione

A perturbation treatment was developed for the comparative study of the abstraction of hydrogen from methane by formaldehyde and thioformaldehyde in their nπ* and ππ* states. Both in-plane and perpendicularplane reactions are considered. Results are qualitative but reveal clearly the prominent distinguishing features of these two photochemical processes in agreement with the experimental observations.

Quest for new materials: Inorganic chemistry plays a crucial role

There is an endless quest for new materials to meet the demands of advancing technology. Thus, we need new magnetic and metallic/semiconducting materials for spintronics, new low-loss dielectrics for telecommunication, new multi-ferroic materials that combine both ferroelectricity and ferromagnetism for memory devices, new piezoelectrics that do not contain lead, new lithium containing solids for application as cathode/anode/electrolyte in lithium batteries, hydrogen storage materials for mobile/transport applications and catalyst materials that can convert, for example, methane to higher hydrocarbons, and the list is endless! Fortunately for us, chemistry - inorganic chemistry in particular - plays a crucial role in this quest. Most of the functional materials mentioned above are inorganic non-molecular solids, while much of the conventional inorganic chemistry deals with isolated molecules or molecular solids. Even so, the basic concepts that we learn in inorganic chemistry, for example, acidity/basicity, oxidation/reduction (potentials), crystal field theory, low spin-high spin/inner sphere-outer sphere complexes, role of d-electrons in transition metal chemistry, electron-transfer reactions, coordination geometries around metal atoms, Jahn-Teller distortion, metal-metal bonds, cation-anion (metal-nonmetal) redox competition in the stabilization of oxidation states - all find crucial application in the design and synthesis of inorganic solids possessing technologically important properties. An attempt has been made here to illustrate the role of inorganic chemistry in this endeavour, drawing examples from the literature its well as from the research work of my group.

Studies of phosphazenes. 28. Reactions of pentachloro- and pentafluoro(triphenylphosphazenyl)cyclotriphosphazenes with sodium methoxide. Mechanistic aspects and their implications for nucleophilic displacement at a tetrahedral phosphorus(V) center

Abstract is not available.

Comments on "Room temperature interfacial reactions in electrodeposited Au/Sn couples"

Recently, Tang et al. (Acta Mater. 56 (2008) 5818) published a paper explaining room temperature growth of the phases in the Au/Sn system. In their analysis, they considered Au as the only mobile species for all the product phases, and Sn as virtually immobile. It is shown here that this analysis is not correct, since Sn has a higher diffusion rate through the AuSn4 phase. On the other hand, the mobilities of species in the AuSn2 phase are as yet unknown.

Metallomicelles as potent catalysts for the ester hydrolysis reactions in water

Synthetic amphiphiles have been employed for the investigation of diverse topics, e.g. membrane mimetics, drug delivery, ion sensing and even in certain separation processes. Metal-complexing amphiphiles comprise an interesting class of compounds possessing multiple utilities. Upon solubilization in water they form metallomicelles. For achieving specific catalysis of a variety of reactions, metallomicelles were utilized by applying the principles of coordination chemistry and self-organizing systems. Because of their certain similarities with the natural enzymes, metallomicelles were synthesized as catalysts for many reactions. In particular the metallomicelles play a catalytic role in reactions involving the hydrolysis of activated carboxylate esters, phosphate esters and amides at ambient conditions near neutral pH. Apart from the hydrolysis reactions, these were exploited to play pertinent role as Lewis acid catalysts in cycloaddition reactions, and in other reactions such as phenolic oxidation in presence of hydrogen peroxide. In this review we emphasize with the help of assorted examples, the design, synthesis of metal-complexing amphiphiles and their aggregation behavior leading to catalytic hydrolysis reactions in aqueous media.

Effectiveness factor for zeroth-order catalytic reactions with volume change and nonuniform catalyst activity profiles

Analytical solutions are presented for the effectiveness factor of a zeroth-order reaction with volume change and nonuniform catalyst activity profile in slab, cylinder and spherical pellets. The possibility of shape normalization is considered for a variety of activity profiles and pellet shapes. When the catalyst activity at the external surface of the pellet is non-zero, shape normalization is obtained, which makes the asymptotic behavior of the effectiveness factor identical for small and large values of Thiele modulus, however, the normalization can lead to significant errors, particularly for the case of activity profiles decreasing towards the outer surface of the catalyst.

Preparative solid state chemistry. Recent developments

A survey of recent developments in preparative solid state chemistry shows that, with a knowledge of structural chemistry and reactivity patterns of solids, it is possible to synthesize a variety of new solids possessing novel structures. A distinction is made between synthesis ofnew solids and synthesis of solids bynew methods. Three new routes to solid state synthesis are recognized: the precursor method, and topochemical methods involving redox and ion-exchange reactions. The low-temperature topochemical methods enable synthesis of metastable phases that are inaccessible by the high temperature route. Several illustrative examples of solid state synthesis from the recent literature are presented.

Adriamycin affects plasma membrane redox functions

Adriamycin (Doxorubicin) stimulates NADH oxidase activity in liver plasma membrane, but does not cause NADH oxidase activity to appear where it is not initially present, as in erythrocyte membrane. NADH dehydrogenase from rat liver and erythrocyte plasma membranes shows similar adriamycin effects with other electron acceptors. Both NADH ferricyanide reductase and vanadate-stimulated NADH oxidation are inhibited by adriamycin, as is a cyanide insensitive ascorbate oxidase activity, whereas NADH cytochrome c reductase is not affected. The effects may contribute to the growth inhibitory (control) and/or deleterious effects of adriamycin. It is clear that adriamycin effects on the plasma membrane dehydrogenase involve more than a simple catalysis of superoxide formation.

Michael Reactions of the Anions generated by the Metal-Ammonia Reduction of Benzoic Acids.

A novel method for the construction of carboncarbon bonds is described in which anions obtained by the metal-ammonia reduction of benzoic acid and its derivatives undergo ready Michael reaction with methyl crotonate to give the addition products.

Kinetic studies of the reactions of hexachlorocyclotriphosphazene and octachlorocyclotetraphosphazene with t-butylamine

The rates of the reactions of hexachlorocyclotriphosphazene (N3P3Cl6) and octachlorocyclotetraphosphazene (N4P4Cl8) with t-butylamine in methyl cyanide were determined at three temperatures in the range 273–308 K. The reaction of N3P3Cl6 was also studied in tetrahydrofuran. Rigorous purification of the chlorophosphazenes and the solvents was essential to obtain reproducible results. An SN2(P) mechanism involving the formation of a five-co-ordinate phosphorus intermediate is in accord with the kinetic data. The greater reactivity of N4P4Cl8 compared to that of N3P3Cl6 arises entirely from the lowering of the enthalpy of activation. The effects of ring size and the solvent on the rates are discussed in terms of the activation parameters.