Studies on Energetic (Non) Compounds. Part 21: Preparation and thermal decomposition of ring substituted dimethyl anilinium bromides

Six isomeric dimethyl anilinium bromides (DMABr) have been prepared and characterized by elemental and spectroscopic studies. Thermal decomposition of these salts has been studied by TG and simultaneous TG-DTA techniques. Kinetic parameters have been evaluated from isothermal TG data using contracting area and contracting cube equations. The decomposition pathways have also been suggested which involves simultaneous sublimation (at lower temperature) and dissociative vaporization/decomposition (at higher temperature). This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of nonthermal ion distribution and dust temperature on nonlinear dust acoustic solitary waves

The effects of nonthermal ion distribution and finite dust temperature are incorporated in the investigation of nonlinear dust acoustic waves in an unmagnetized dusty plasma. Sagdeev pseudopotential method which takes into account the full nonlinearity of plasma equations, is used here to study solitary wave solutions. Possibility of co-existence of refractive and compressive solitons as a function of Mach number, dust temperature and concentration of nonthermal ions, is considered. For the fixed value of nonthermal ions, it is found that the effect of increase in dust temperature is to reduce the range of co-existence of compressive and refractive solitons. Particular concentration of nonthermal ions results in disappearance of refractive solitons while the decrease in dust temperature, at this concentration restores the lost refractive solitons.     

Thermal Studies on Some Biologically Active Organomercury(II) Complexes

Thermal behaviour of a number of organomercury(II) complexes of the type, p-XC₆H₄HgCl(L¹) (I), p-XC₆H₄HgCl₃(L²) (II), p-XC₆H₄HgL³ (III) and p-XC₆H₄HgL⁴ (IV) [L ¹=isoniazid, L ²=theobromine, L ³=phenyldithiocarbamate, L ⁴=p-nitrophenyldithiocarbamate; X=Me, MeO, NO₂] has been investigated. From TG curves, the order and activation energy of the thermal decomposition reaction have been elucidated. The variation of the activation energy has been correlated with the nature of the substituent on the phenyl ring. The heat of reaction has been elucidated from DSC or DTA studies. The fragmentation pattern has been analysed on the basis of mass spectra.This revised version was published online in November 2005 with corrections to the Cover Date.A part of this work was carried out at Intitute of Microbial Technology, Chandigarh, under the Visiting Associateship Scheme (1992–95) of the Council of Scientific and Industrial Research, New Delhi.     

Fourier transform infrared spectral study of N,N′-dimethylformamide-water-rhodamine 6G mixture

Infrared absorption spectra of N,N′-dimethyl formamide in the absence and presence of water, rhodamine 6G and water–rhodamine 6G mixture are reported. Assignment of observed bands has been made on the basis of density functional theory calculations and available assignments in the literature. Certain bands show changes in their positions and intensities when water is added to N,N′-dimethylformamide. This is due to hydrogen bonding interaction between these molecules. Similar changes are also observed for dimethylformamide and Rh6G mixture to a lesser extent. The presence of Rh6G in a dimethylformamide–water mixture reverses these spectral changes due to preferential solvation of Cl^? by water molecules. Solvation reduces or nullifies the hydrogen bonding between dimethylformamide and water in the mixture.     

Duality in inexact fractional programming with set-inclusive constraints

This paper extends the fractional programming problem with set-inclusive constraints studied earlier by replacing every coefficient vector in the objective function with a convex set. A dual is formulated, and well-known duality results are established. A numerical example illustrates the dual strategy to obtain the value of the initial problem.The research of the first author was conducted while he was on sabbatical at the Department of Operations Research, Stanford University, Stanford, California. The financial assistance of the International Council for Exchange of Scholars is gratefully acknowledged. The author is grateful to the Department of Operations Research at Stanford for the use of its research facilities.     

Forced Degradation Study on Gliclazide and Application of Validated Stability-Indicating HPLC-UV Method in Stability Testing of Gliclazide Tablets

Forced degradation study on gliclazide was conducted under the conditions of hydrolysis, oxidation, dry heat and photolysis and an isocratic stability-indicating HPLC-UV method was developed and validated. All the seven degradation products (I–VII) formed under different conditions were optimally resolved on a C₁₈ column with mobile phase composed of 40% acetonitrile and 60% ammonium acetate solution (0.025 M, pH 3.5) at a flow rate of 0.25 mL min^?1 using 235 nm as detection wavelength. The method was linear between 5–500 μg mL^?1 drug concentrations. The %RSD of intra- and inter-day precision studies was <1 and <2% respectively. Excellent recoveries (99.81–100.97%) proved the method sufficiently accurate. Each peak resolved always with a resolution of >1.90 indicating the method to be rugged enough. The method was used to study the drug degradation behaviour under the forced conditions. Four degradation products (I–IV) were formed in 0.1 N HCl and water whereas only I and III were formed in 3% H₂O₂. Two new products V and VI in addition to I, III and IV were formed in 0.1 N NaOH. The drug was stable to thermal and photolytic decomposition. The degradation behaviour in water and 0.1 N NaOH was similar under dark and light conditions but a new product VII was formed in 0.01 N HCl in light. In general, the rate of degradation was accelerated by the light. The method was applied successfully in stability testing of gliclazide tablets.     

Metal complexes of hybrid oxygen — arsenic ligands. Part I. Complexes ofo-dialkyl/arylarsinobenzoic acids with chromium(III)

Summary Reactions of hybrid oxygen-arsenic ligands:o-R₂As-C₆H₄CO₂H (R = Me, Et, C₆H₁₁, Ph andp-tolyl) with CrO₃ and of their sodium salts withtrans-[CrCl₂(H₂O)₄]Cl·2H₂O in a 31 molar ratio yield three types of oxo/hydroxo bridged complexes:a. CrO(o-R₂AsC₆H₄CO₂)nH₂O (R=Me, n=1.5 or 2.5; R=Et, n=1 or 1.5; R=C₆H₁₁, n=1 or 3; R=p-tolyl, n=4),b. Cr(o-Ph₂AsC₆H₄CO₂)₂(OH)2.5 H₂O andc. Cr(o-R₂AsC₆H₄CO₂)(OH)₂nH₂O (R=Ph, n=1; R=p-tolyl, n=0.5). Their i.r. data favour symmetrical chelation of the carboxylate ion, with the metal ion leaving the arsenic(III) uncoordinated. Suitable dimeric, trimeric and tetrameric structures have been assigned for (i) Typea (R=C₆H₁₁, n=1), (ii) Typea (R=p-tolyl, n=4) and (iii) typea. (R= Et, n=1), Typeb. and Typec. (R=p-tolyl, n=0.5) complexes respectively on the basis of solution spectra and experimental molecular weights and _eff values. Calculated ligand field parameters (10 Dq and B) for all the complexes indicate covalent interaction between the metal ion and the ligands.     

Anion receptor functions of lanthanide tris(beta-diketonate) complexes: naked eye detection and ion-selective electrode determination of Cl- anion

Lanthanide tris(fluorinated beta-diketonates) acted as effective receptors of Cl- anion in luminescence sensing and ion-selective electrode systems via highly coordinated complexation.     

1D and 2D NMR studies of N-vinylcarbazole/butyl methacrylate copolymers

Copolymers containing N-vinylcarbazole (V) and butyl methacrylate (B) units of different compositions were synthesized and their compositions were determined from quantitative ¹³C{¹H} NMR spectroscopy. The reactivity ratios of the comonomers were estimated using the Kelen-Tudos and non-linear error in variable methods. The complete spectral assignment in terms of compositional and configurational sequences of the overlapping ¹H and ¹³C{¹H} spectra of the copolymers were done with the help of distortionless enhancement by polarization transfer, 2D heteronuclear single quantum correlation and total correlated spectroscopy experiments.     

Mössbauer effect studies on sodium hexa/carboxylato/ ferrates/III/

Mössbauer spectra of a series of the complexes of the type Na₃[Fe/RCOO/₆]xH₂O /R=H, CH₃, C₂H₅, C₆H₅/ has been recorded at 298±2 K. All display a quadrupole doublet with isomer shift and quadrupole splitting values in agreement with high spin iron/III/ octahedral geometry. The quadrupole splitting show an increasing trend with increasing polarizability of the substituent anion /RCOO^–/. A linear correlation between quadrupole splitting values and the /Fe–O/ stretching frequencies has also been observed.