Separation of Multicomponent Mixture of Naphthalene Derivatives by Reversed-Phase High-Performance Liquid Chromatography

Separation of a mixture of naphthalene derivatives by reversed-phase high-performance liquid chromatography with UV detection was studied. Chromatographic characteristics were calculated for nine compounds, including naphthalene.     

Kinetics of thermolysis of sterically hindered phenols used as polymeric material stabilizers

The thermolysis kinetics of a series of sterically hindered phenols was studied.     

Convergent-Divergent Nozzle under Highly Overexpanded Conditions

Quantitative results for the thrust and flow-rate performance of axisymmetric nozzles in highly overexpanded regimes are presented. Estimates for the lateral component of the reactive force and its range of possible existence are obtained for axisymmetric nozzles differing in the divergent region geometry. Empirical formulas for the gas flow rate in the subcritical outflow regime and the pressure range on which this regime can take place are proposed.     

Estimation of thermal stability of phenol stabilizers by means of thermogravimetric analysis

A new method was developed for evaluation of the results of thermal analysis of phenol stabilizers used for the thermal stabilization of light-coloured polymers. The integral observed decomposition temperature obtained by using Doyle's method from the thermogravimetric curves was used as a basis of approach. For this purpose, the computational program TERMOGRAF for PC/AT is suggested. It is considered that the integral observed decomposition temperature is a more reliable and reproducible characteristic of thermal stability than the approach based on the temperature of beginning of decomposition.     

Supramolecular structure of 6-phenyl-2-chloropyrimidine-4-carboxamide and its complexes with dioxane and ethanol

A stable 2:1 complex of 6-phenyl-2-chloropyrimidine-4-carboxamide with dioxane has been synthesized. The structure of the complex was investigated by molecular spectroscopy (chloroform solution), thermoderivatography, and XRD (crystalline phase). A supramolecular structure is formed in the crystal of the complex, which involves centrosymmetric dimer associates of amide molecules, linked by dioxane molecules and intermolecular hydrogen bonds into infinite stepwise ribbons. These ribbons are stacked via π-stacking pair interactions “amidopyrimidine-amidopyrimidine.” The complex of the same 2:1 carboxamido derivative of pyrimidine with ethanol is unstable and has a different structure. The ethanol molecules lie in the vacant voids of the stacks formed by the “amidopyrimidine-amidopyrimidine” synthon.     

Thermal Decomposition of Spatially Hindered Phenols Using Chromatomass-spectrometric System

The present paper deals with thermal decomposition of some spatially hindered phenols, which are in the industry as stabilizers in synthetic materials used. The investigated stabilizers are separated to two groups in respect to mechanism of decomposition (group I and II). This assumption was confirmed by chromatomass-spectrometric investigations. It allows a stabilizer for forming a plastic with variety properties to choose. This revised version was published online in August 2006 with corrections to the Cover Date.     

Extraction-spectrophotometric determination of selenium in organoselenium compounds using aromatic o-diamines

Procedures for the extraction-spectrophotometric determination of selenium in organoselenium compounds using a new reagent, 1,2-diamino-3,4,5,6-tetrafluorobenzene (DAFB), and a known reagent, 2,3-diaminonaphthalene (DAN), are developed. Complexes of DAFB or DAN with selenium(IV) are extracted with toluene, and the absorbance of the extracts is measured. The optimal conditions for the determination were found, and the spectrophotometric characteristics were determined. The calibration curves are linear in the range of selenium concentrations of 1–10.6 mg/L (DAFB) and 1–9.1 mg/L (DAN). Nitrogen, chlorine, bromine, fluorine, and sulfur present in organoselenium compounds do not interfere with the determination of selenium. The relative error of determination does not exceed ±2%.     

The characteristics of the grazing interaction of fast electrons with dielectric surfaces

Experimental data on the mechanism of the grazing interaction of fast electron beams with planar dielectric surfaces of various materials are analyzed. New experimental results regarding the grazing interaction between electrons with an energy of 10 keV and metalized structured surfaces are reported. The difference between the processes of the interaction of fast electron beams with planar and structured surfaces is demonstrated.     

Compensation Effect in the Kinetics of Spatially Hindered Phenols

This paper reports a linear relationship between kinetic characteristics from the Arrhenius equation describing a decomposition process found when studying the kinetics of thermolysis of spatially hindered phenols. This relationship between the coefficients is known in the literature as a 'compensation effect'. The existence of the compensation effect permits some conclusions concerning the decomposition mechanism and thermal characteristics of the compounds under investigation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Elemental analysis of organic compounds with the use of automated CHNS analyzers

Results of many years’ worth of studies on the determination of carbon, hydrogen, and nitrogen on automated CHNS analyzers were summarized. Catalytic oxide compositions were selected that allow for the analysis of synthetic and natural organic compounds and materials of any elemental composition and structure: polycyclic, condensed aromatic, heterocyclic, carbonaceous (graphites and carbons), organometallic, organoelement, etc.