Synthesis of Thermally Stable Energetic 1,2,3‐Triazole Derivatives

Various thermally stable energetic polynitro‐aryl‐1,2,3‐triazoles have been synthesized through Cu‐catalyzed [3+2] cycloaddition reactions between their corresponding azides and alkynes, followed by nitration. These compounds were characterized by analytical and spectroscopic methods and the solid‐state structures of most of these compounds have been determined by using X‐ray diffraction techniques. Most of the polynitro‐bearing triazole derivatives decomposed within the range 142–319 °C and their heats of formation and crystal densities were determined from computational studies. By using the Kamlet–Jacobs empirical relation, their detonation velocities and pressures were calculated from their heats of formation and crystal densities. Most of these newly synthesized compounds exhibited high positive heats of formation, good thermal stabilities, reasonable densities, and acceptable detonation properties that were comparable to those of TNT.     

Comparative Study of Catalytic Potential of TBAB,BTEAC, and CTAB in One-Pot Synthesis of 1,4-Dihydropyridines Under Aqueous Medium

Convenient and straightforward tetrabutylammonium bromide (TBAB), benzyltrienthylammonium chloride (BTEAC), and cetyltrimethylammonium bromide (CTAB) catalyzed synthesis of 1,4-dihydropyridines (1,4-DHPs) in water was established for the first time. The catalytic potential of phase-transfer catalysts (PTCs) in three different concentrations was envisioned. Aryl aldehydes and hetero aryl aldehydes afforded good yields of 1,4-DHPs in TBAB and BTEAC reactions. In particular, furfuraldehyde and thienyl-2-carbaldehyde produced excellent yields. Isolation of the products through nonchromatographic methods, good to excellent yields, and benign reaction conditions are the major advantages of this protocol.     

Stretching and collapse of neutral polymer layers under association with ionic surfactants

We provide experimental evidence for stretching and collapse of neutral polymer layers, already adsorbed at an oil-in-water interface, due to its interaction with surfactants. Upon stretching, the first interaction length (2L(0)) follows a power law dependence on surfactant concentration ( proportional, variant C(x)(s), where x approximately 0.5 for cationic surfactants) and collapses in the presence of salt, as a relatively weak power law (C(-y)(s), where y=0.17), in good agreement with brush length decay for polyelectrolyte brushes.     

Base catalyzed rearrangement of some bicyclic ketol acetates.

The ketol $\text{3a}$ and its acetate $\text{3b}$ when refluxed in methanolic potassium hydroxide (5%) were found to rearrange to 4-methyl-8-acetyl-5,6,7,8-tetrahydro-1-naphthol $\text{4}$. The epimeric acetate $\text{3c}$ also behaved likewise. A mechanism is suggested for the rearrangement.     

Cyclic voltammetric measurements of growth of Aspergillus terreus.

A detailed study using the cyclic voltammogram was done on the live cells of Aspergillus terreus. The peak current values were obtained for different days of growth and plotted against time. The response of cyclic voltammogram showed the phases of the growth of the fungus. The growth curve obtained matched well with the conventional methodology, which assesses the increase of dry weight of the organisms against time. The electrochemical method is more advantageous because it is easy to assess and consumes less time. Further the electrochemical method clearly shows the decline phase which is generally not very defined in the conventional method of assessment of the growth curve. It was confirmed by further experiments that the metabolites were responsible for the anodic peak and not the biomass. Further work is in progress in order to analyze the metabolite(s) that is/are responsible for the anodic peak.     

Modulated phases in the Falicov-Kimball model

The arrangement of localized f electrons in the ground state of the Falicov-Kimball model is studied as a function of the energy of the f-level. For the half-filled case in one dimension, perturbation theory in the d-electron bandwidth together with numerical results reveals a sequence of transitions between long-period modulated arrangements of the f electrons. Results suggest the existence of a multiphase point at zero d-band-width and f energy, and a complete devil's staircase for the variation of f occupation as the energy of the f-level is changed when the d-bandwidth is nonzero.     

An Efficient N‐Arylation of Heterocycles with Aryl‐, Heteroaryl‐, and Vinylboronic Acids Catalyzed by Copper Fluorapatite

N‐Arylation of N‐containing heterocycles, such as pyrazoles, imidazoles, and benzimidazoles with aryl‐, heteroaryl‐, and vinylboronic acids was efficiently carried out by copper fluorapatite (CuFAP) catalyst in MeOH at room temperature under base‐free conditions. The N‐arylated heterocycles were isolated in good‐to‐excellent yields.     

Effect of addition of a non-equidiffusional reactant to an equidiffusional diffusion flame

A Burke–Schumann (flame-sheet) formulation is developed for diffusion flames between a fuel and oxidiser with Lewis numbers of unity, subject to addition to the fuel and/or oxidiser stream of a different reactant for which the Lewis number differs from unity. This formulation is applied to laminar counterflow diffusion-flame experiments, reported here, in which hydrogen was added to either methane–nitrogen mixtures or oxygen–nitrogen mixtures at normal atmospheric pressure, with both feed streams at normal room temperature. Experimental conditions were adjusted to fix selected values of the stoichiometric mixture fraction and the adiabatic flame temperature, and the strain rate was increased gradually, maintaining the momentum balance of the two streams, until extinction occurred. At the selected sets of values, the strain rate at extinction was measured as a function of the hydrogen concentration in the fuel or oxidiser stream. The ratio of the fraction of the oxidiser flux that consumes hydrogen to the fraction that consumes fuel was calculated from the new Burke–Schumann formulation, and it was found that, within experimental uncertainty, the ratio of the extinction strain rate with hydrogen addition to that without was the same at any given value of this oxygen flux ratio, irrespective of whether the hydrogen was added on the fuel or oxidiser side. This experimental result was also in close agreement with computational predictions employing detailed chemistry. These results imply that differences in detailed hydrogen concentration profiles within the reaction zone have little or no influence on the chemical kinetics of extinction when the stoichiometric mixture fraction, the adiabatic flame temperature, and the proportion of oxygen that consumes the added fuel are fixed. This same correspondence may be expected to apply for other fuels and additives.     

Effect of isomeric butanols on the temperature corresponding to the adiabatic compressibility minimum of water

The effect of isomeric butanols on the temperature corresponding to the adiabatic compressibility minimum of water (T _β) was studied using a variablepath interferometer working at 3 MHz. The structural contribution to the shift inT _β, [ΔT _βstr]_exp, was found to be positive and to increase with concentration to a maximum atX ₂?0.0193, 0.0100, and 0.0090 fort-butanol, sec-butanol, and isobutanol, respectively. The results have been explained on the basis of stabilization of water structure at low concentrations of alcohol. The quantity [ΔT _βstr]_exp forn-butanol is practically zero at low concentrations, while at high concentrations it is negative, indicating rupture of the hydrogen-bonded structure of water by this solute. At any given concentration,t-butanol > sec-butanol > isobutanol >n-butanol is the order of increasing structural contribution to the shift inT _β. Theoretical values of the structural contribution to the shift inT _β are in good agreement with the experimental data.