A new one-pot three-component condensation reaction for the synthesis of 5-deaza-5,8-dihydropterins

The one-pot cyclocondensation of 2,6-diaminopyrimidin-4-one, an aromatic or aliphatic aldehyde and a beta-ketoester in acetic acid, or dimethyl sulfoxide in the presence of zinc(II) bromide, under thermal conditions provided dihydropyrido[2,3-d]pyrimidin-4(3H)-ones in good yield and with total regiocontrol.     

FT-IR and Raman spectroscopic study of hydrated rubidium (cesium) borates and alkali double borates

FT-IR and Raman spectra of five hydrated alkali borates and five hydrated alkali double borates have been recorded at room temperature in the range 400 to 4000 cm⁻¹, and analyzed. Fundamental vibrational modes have been identified and assignments tentatively made in comparison with the work of Janda and Heller, and Li Jun. The text was submitted by the authors in English.     

Preparation of solutions of amidomagnesium chlorides in poly(ethylene oxide) and their characterization by conductivity measurements

Polymer electrolyte systems were prepared for the first time by dissolution of amidomagnesium chlorides in poly(ethylene oxide), (PEO). For the preparation, solutions of (hexamethyldisilylamido)magnesium chloride, (dimethylpyrrolyl)magnesium chloride, (diisopropylamido)magnesium chloride, piperidinomagnesium chloride and morpholinomagnesium chloride were chosen. The composition of these polymer electrolyte systems corresponds to the general formula R₂NMgCl·P(EO)_n·THF. Most work has been done with the system (hexamethyldisilylamido)magnesium chloride in PEO, (Me₃Si)₂NMgCl·P(EO)_n·THF, with n= 3, 4, 5, or 7. The electrolytes have a soft rubber-like consistency. At 30 °C, electrical conductivities of 10⁻⁶–10⁻⁵ S/cm were found. The conductivities were measured in the temperature range 20–60 °C. Within this temperature range a linear dependence of the logarithms of the conductivity on the inverse temperature was found and activation energies for the conducting process of 30–60 kJ/mol were calculated. Using those polymer electrolytes with a high content of the amidomagnesium compound, a reversible magnesium deposition takes place by cathodic reduction at potentials below −1.9 V vs. a Ag/AgCl reference electrode. These polymer electrolytes were found to be stable against oxidation up to about −0.3 V vs. Ag/AgCl. Electronic Publication     

Mixed micellization of an anionic gemini surfactant (GA) with conventional polyethoxylated nonionic surfactants in brine solution at pH 5 and 298 K

The micellization behavior of an anionic gemini surfactant, GA with nonionic surfactants C₁₂E₈ and C₁₂E₅ in presence of 0.1 M NaCl at 298 K temperature, has been studied tensiometrically in pure and mixed states, and the related physicochemical parameters (cmc, γ _cmc, pC ₂₀, Γ _max, and A _min) have been evaluated. Tensiometric profile (γ vs log [surfactant]), for conventional surfactants, generally consists of a single point of intersection; a gradually decreasing line (normally linear, or with slight curvature) ultimately saturates in γ at a particular [surfactant], corresponding to complete monolayer saturation. The gemini, in this report, led to two unequivocal breaks in the tensiometric isotherm. An attempt to the interpretation of the two breaks from molecular point of view is provided, depending solely on the chemical structure of the surfactant. The gemini, even in mixed state with the conventional nonionic surfactants C₁₂E₅ and C₁₂E₈, manifested the dual breaks; of course, the dominance of the feature decreases with increasing mole fraction of the nonionics in the mixture. Theories of Clint, Rosen, Rubingh, Motomura, Georgiev, Maeda, and Nagarajan have been used to determine the interaction between surfactants at the interface and micellar state of aggregation, the composition of the aggregates, the theoretical cmc in pure and mixed states, and the structural parameters according to Tanford and Israelachvili. Several thermodynamic parameters have also been predicted from those theories.     

Surface Modification of Fine Particles with a SnO<Subscript>2</Subscript> Film by Using a Polyhedral-Barrel Sputtering System

Fine particles were modified with a thin film of SnO₂ by using a barrel sputtering system that is a dry process. The conditions for the preparation of SnO₂ were studied by reactive sputtering onto a glass plate substrate. The optimal conditions for the preparation of tetragonal SnO₂ were identified as 60% partial oxygen pressure and 1.0 Pa total gas pressure with the substrate at room temperature. Under the optimized conditions, the surfaces of Al flake particles were modified with a thin film of SnO₂. XRD and SEM/EDS analysis of the prepared samples showed that the Al particle surfaces were uniformly modified by a thin film of SnO₂ in all cases. The film thicknesses were 80, 130, and 180 nm at RF outputs of 195, 350, and 490 W. These measured thicknesses coincided with the values estimated from the interference colors of the samples.     

Mesoporous material as catalyst for the production of fine chemical: Synthesis of dimethyl phthalate assisted by hydrophobic nature MCM-41

Aluminum, iron and zinc containing MCM-41 molecular sieves were prepared by the hydrothermal method. The catalyst was characterized by the XRD, BET (surface area), FT–IR and ²⁹Si, ²⁷Al MAS–NMR techniques. The catalytic activity of these molecular sieves was tested with esterification reaction used with phthalic anhydride (PAH) and methanol (MeOH) in the autoclave at 135 °C, 150 °C and 175 °C. Conversion increases with an increase in temperature and mole ratio. The activity of these catalysts followed the order: Al-MCM-41 (112) > Fe-MCM-41 (115) > Al-MCM-41 (70) > Al-MCM-41 (52) > Fe-MCM-41 (61) > Al, Zn-MCM-41 (104) > Al-MCM-41 (30). The reaction yielded both monomethyl phthalate (MMP) and dimethyl phthalate (DMP). The nature of the catalyst sites has been proposed using with water as an impurity. The selectivity of the dimethyl phthalate increases with increase in temperature and mole ratio. The weight of the catalyst was optimized at 0.07 g. The hydrophilic and hydrophobic nature of the catalyst has been explained by the influence of water and the external surface acidity also facilitates the reaction and this has been confirmed by the supporting reaction.     

Study of the reaction of chalcone analogs of dehydroacetic acid and o-aminothiophenol: synthesis and structure of 1,5-benzothiazepines and 1,4-benzothiazines

Treatment of α,β-unsaturated carbonyl compounds, obtained by the reaction of DHA and aromatic (or heteroaromatic) aldehydes, with o-aminothiophenol results in the formation of 1,5-benzothiazepines and/or 1,4-benzothiazines depending upon the reaction conditions and structure of the aldehydes. The products were characterized by the combined use of multinuclear 1D and 2D NMR and GIAO/DFT calculations of ¹H, ¹³C and ¹⁵N chemical shifts. The tautomerism of these compounds in solution was determined, they have an exocyclic CC double bond.     

The effect of vibrational bond stretching on rotational inelastic electron-molecule scattering

Differential cross sections for state-to-state rotationally inelastic electron-Na₂ scattering, with the molecule being in the vibrational levelv′'=31, are measured at a collision energy of 150 eV. Angular momentum transfer of up to Δj=26 is observed, which is even more than previously obtained for the vibrational ground statev′'=0. Good agreement is found with theoretical results from a spectator scattering model. This work, in general, elucidates the role of vibrational excitation in collision dynamics under vibrationally sudden conditions.     

Studies with an inorganic ion-exchange membrane exhibiting selectivity for Pb(II) ions

A solid membrane electrode made with titanium arsenate as membrane material and "Araldite" as binder has been used to measure the activity of lead in the concentration range from 0.1 M to 5 x 10(-6)M. The electrode is unaffected by many cations, nitrate and acetate. The response time is 40-60 sec over the whole concentration range (in a static system) and the electrode has a working life of at least four months. The electrode can work in the pH range 2-5 and is tolerant of ethanol up to a content of 30% v v . It has been successfully used for end-point indication in potentiometric titration of lead. A membrane treated with cationic surfactant exhibits better selectivity.