Search Results

You are looking at 11 - 20 of 67 items for :

  • All content x
Clear All

Abstract  

1,2,4-triazole-3-one (TO) and guanidine nitrate (GN) have the potential to be used as alternative gas-generating agents. To obtain a better understanding of thermal decomposition properties of TO/GN mixtures, sealed cell differential scanning calorimetry, thermogravimetry–differential thermal analysis–infrared spectroscopy (TG–DTA–IR), and thermogravimetry–differential thermal analysis–mass spectrometry (TG–DTA–MS) were carried out. The endothermic peak and onset temperatures of TO/GN mixtures were lower than those of individual TO and GN. TG–DTA–IR and TG–DTA–MS showed that the mass of TO/GN mixtures decreased with heat generation and N2 evolved as the major gas during thermal decomposition. The interaction between TO and nitric acid from the dissociation of GN is proposed for the thermal decomposition of TO/GN mixtures.

Restricted access

Abstract  

Thermoanalytical study of the pesticide 3-amino-1,2,4-triazole (ATA) has been carried out, using simultaneous DTA-TG in nitrogen flow, in order to know its thermal behaviour and stability. These techniques have been further complemented using evolved gas analysis and mass spectroscopy (EGA-MS). Two different stages of ATA decomposition were observed: after the first decomposition step, a mixture of compounds is obtained, according to MS data, being the principal component a compound of molecular weight 126. It is formed by a first order reaction mechanism, according to the kinetic study, withE a=124±8 kJ·mol−1. The second decomposition step takes place about 735°C, with evolution of HCN and NH3, being the final weight loss 96%.

Restricted access

Lipophilicities of 21 newly synthesized 1,2,4-triazoles, compounds of potential importance as fungicides, have been determined by micellar and reversed-phase planar chromatography. Different stationary and mobile phases were used in the measurements. Chromatographic lipophilicities (log k m and R M0) were correlated with partition coefficients log P (Alog Ps, AClog P, Alog P, Mlog P, KowWin, xlog P2 and xlog P3) calculated from molecular structures. Principal component analysis allowed a more objective comparison of different lipophilicity descriptors determined from various chromatographic systems and calculated theoretically as log P parameters.

Restricted access

Summary

Some new derivatives of thiosemicarbazide and the 1,2,4-triazole of sulphanylacetic acid have been chromatographed on RP-18 HPTLC plates with mobile phases containing water and an organic modifier (methanol, dioxane, acetone, 2-propanol, or tetrahydrofuran). Relationships between solute retention and modifier concentration were described by Snyder's linear equation. The equation was used to determine R M 0 values, by extrapolation, and the S values denoting the slopes of the relationship between linear retention and mobile phase concentration; both values characterize the lipophilicity of the substances. Calculated values of R M 0 were correlated with log P values for the drugs investigated by use of the software HyperChem. Correlations between intercept (R M 0) and slope (S) from the linear equations were also calculated. The effects of different mobile phase modifiers on experimentally obtained lipophilicity were also analysed and compared.

Restricted access

Abstract  

The investigations concerning the thermal behaviour of a series of Ni(II) and Cu(II) complexes of type [NiLCl2mH2O ((1) L:L1, m=6; (3) L:L2, m=4) or [CuLCl]nCln·mnH2O ((2) L:L1, m=6; (4) L:L2, m=4) are presented. The ligands L(1) and L(2) have been synthesised by template condensation of 3,6-diazaoctane-1,8-diamine or 1,2-diaminoethane with formaldehyde and 2-amino-4H-1,2,4-triazole. The bonding and stereochemistry of the complexes have been characterised by IR, electronic and magnetic studies at room temperature. The in vitro qualitative and quantitative antimicrobial activity assays showed that the complexes exhibited variable antimicrobial activity against planktonic as well as biofilm embedded Gram-negative, Gram-positive and fungal strains. The thermal behaviour provided confirmation of the complexes composition as well as the number and nature of water molecules and the intervals of thermal stability.

Restricted access

Field experiments were conducted over 3 years to assess the effects of fungicides (F) containing strobilurins (alone and in mixture with morpholine, triazoles) and triazoles (epoxiconazole or propiconazole) on winter wheat ‘Zentos’ grain quality, incidence of Fusarium head blight (FHB) in the field, grain contamination with fungi and mycotoxins. The effect of strobilurins and triazoles on the parameters tested was more dependent on the weather conditions of the growing season than on the F applied. The incidence of FHB was low in 2002 and 2003, but high in 2004. Averaged data suggest that strobilurin treatments decreased the level of FHB. In 2002, grain contamination with fungi was lower than in 2003 and 2004. The data on the impact of fungicides on post-harvest grain infection with Fusarium spp. and contamination with mycotoxins deoxynivalenol (DON), zearalenone (ZEN) and T-2 were controversial. The fungicides only insignificantly affected protein and gluten concentration in grain, as well as sedimentation and falling number. All grain quality components were especially dependent on the year (significant at P<0.01). However, fungicide application significantly, at P<0.01, increased grain protein and gluten yields: they were higher for the strobilurin-treated plots (with a small exception) than for the untreated and those treated with propiconazole.

Restricted access

The purpose of this paper was to assess the suitability of thin-layer chromatography (TLC) as a pilot method for high-performance liquid chromatography (HPLC). The new 1,2,4-triazole and thiosemicarbazide derivatives were analyzed by use of reversed-phase (RP)-TLC and RP-HPLC techniques, applying octadecyl silica adsorbents and aqueous-organic mobile phases. Organic modifiers: methanol and acetonitrile were used at appropriate concentrations providing optimal retention factors. For both techniques, retention coefficient k in column chromatography and the retardation factor R F expressing retention in TLC were determined. The experimentally measured parameters were presented in a logarithmic scale as log k and R M, respectively. The constructed relationships between log k and R M allowed determining the possibility of TLC for anticipating HPLC retention behavior.

Restricted access

As it was shown in earlier experiments, magnetic field can influence various processes taking part in nature. One of them might be the permeation of chemical compounds across biological membranes. An excellent tool for investigations on that subject is chromatography. Basing on retention measurements performed using reversed-phase thin-layer chromatography (RP-TLC) and micellar liquid chromatography—thin-layer chromatography (MLC—TLC), descriptors of lipophilicity were calculated for the group of 1,2,4-triazole derivatives. The experiments were performed in moderate (≈0.4 T) magnetic field and simultaneously outside it. The analysis of the obtained data showed that the presence of an external static magnetic field can alternate the obtained descriptor values which allows to assume that the ability of passive permeation of the investigated substances across cellular membrane also changes. The intensity of changes depends on the structure of the chromatographed substance and the lipophilicity measurement method.

Restricted access

Abstract  

A novel complex [Ni(H2O)4(TO)2](NO3)2·2H2O (TO = 1,2,4-triazole-5-one) was synthesized and structurally characterized by X-ray crystal diffraction analysis. The decomposition reaction kinetic of the complex was studied using TG-DTG. A multiple heating rate method was utilized to determine the apparent activation energy (E a) and pre-exponential constant (A) of the former two decomposition stages, and the values are 109.2 kJ mol−1, 1013.80 s−1; 108.0 kJ mol−1, 1023.23 s−1, respectively. The critical temperature of thermal explosion, the entropy of activation (ΔS ), enthalpy of activation (ΔH ) and the free energy of activation (ΔG ) of the initial two decomposition stages of the complex were also calculated. The standard enthalpy of formation of the new complex was determined as being −1464.55 ± 1.70 kJ mol−1 by a rotating-bomb calorimeter.

Restricted access

The reversed-phase thin layer chromatographic retention behavior of some new derivatives of 1,2,4-triazole and thiosemicarbazide has been determined. Linear relationships were established between the retention ( R M ) of each solute and the volume fraction of organic modifier (methanol or acetonitrile) in organic-aqueous mobile phases. This enabled determination of chromatographic lipophilicity data — R MW values by extrapolation, ϕ 0 by interpolation for each organic modifier, and S denoting the slope of the linear dependences. Moderate correlation was established between chromatographic lipophilicity and log P G calculated by use of Chem Plus software. Experimental lipophilicity log P TLC was also determined for each solute by the use of a special calibration plot prepared by use of selected sulfonamide standards for the two mobile phase systems used in this study. The effect of different mobile-phase modifiers on experimentally obtained lipophilicity was studied and compared.

Restricted access