Radiation-induced transformations of threonine and its derivatives in aqueous solutions

It was found that the presence of the α,β-aminoalcohol group in the molecules of the hydroxyl-containing amino acid threonine and its derivatives is responsible for their ability to undergo free-radical degradation with C-C bond cleavage. This degradation occurs by the fragmentation of the nitrogen- and carbon-centered radicals of the initial substances.     

Radiation polymerization of 2-acrylamido-2-methylpropanesulfonic acid in aqueous solutions

The dependence of the yield of polymer and its molecular mass on the absorbed dose of γ-irradiation of a 0.8 M 2-acrylamido-2-methylpropanesulfonic acid aqueous solution was determined, as well as the gel fraction of the polymer produced. The feasibility of obtaining a crosslinked polymer via radiation polymerization of 2-acrylamido-2-methylpropanesulfonic acid in the presence of N,N′-methylenebisacrylamide admixtures was shown. It was found that the maximal degree of crosslinking is reached at a dose on the order of 20 kGy and the maximal water uptake (1150 g/g) is achieved at a dose of 1.25 kGy.     

Molecular clusters in aqueous solutions of pyridine and its methyl derivatives

Small-angle neutron scattering proved that molecules in aqueous solutions of pyridine, 2-methylpyridine and 2,6-dimethylpyridine form clusters. The clusters are dynamic aggregates consisting of hydrogen-bonded water-amine complexes. Strengthening of the hydrogen bonds between water and amine molecules due to the methyl groups in the ortho position in the pyridine ring makes the structures more stable, as was evidenced by relatively long times of the structural relaxation. The strong intermolecular forces affect the thermal expansion of the systems. No aggregates similar to those in aqueous systems are present in the methanolic ones. That points to the crucial role of water in the molecular clustering. A molecule of methanol, although capable of hydrogen bonding with the amines, cannot participate in larger structures because of the lack of protons that could form the enhanced network. Thus, even if the amine-methanol complexes occur, they are incapable of further association. It was shown that the co-operative nature of hydrogen bonds and the propensity of water to association are the main factors that determine the properties of aqueous systems.     

Interactions of xanthine and its derivatives with cyclodextrins in aqueous solutions

Using calorimetry, ¹H NMR, UV spectroscopy, and solubility methods, the interactions of natural and hydroxypropylated 6h-, β-, and γ-cyclodextrins with xanthine and its methylated derivatives (theophylline, theobromine, and caffeine) were studied in aqueous solutions at 298.15 K. Cyclodextrins revealed low complexation ability toward xanthine and its methylated derivatives. Hydroxypropyl-γ-cyclodextrin with the largest internal cavity is the most effective solubilizing agent for this type of compounds. The calculated thermodynamic parameters are discussed in terms of structural effects of cyclodextrins and purine alkaloids on the character of their intermolecular interactions in aqueous medium.     

Dielectric spectroscopy on aqueous solutions of pyridine and its derivatives

The complex (dielectric) permittivity has been measured as a function of frequency between 1 MHz and 40 GHz for aqueous solutions of pyridine, 2- and 3-methylpyridine, as well as 2,4- and 2,6-dimethylpyridine at various temperatures and solute concentrations. Different relaxation spectral functions are used to analytically represent the data, in particular the Cole-Cole function. The solute contribution to the extrapolated static permittivity has been calculated to show that, in correspondence with other aqueous solutions of organic molecules and ions, the permittivity of the solvent seems to be enhanced with respect to the pure water value. Also in accordance with other aqueous systems it is found that the principal dielectric relaxation time for equimolar solutions of stereo isomers at the same temperature may significantly differ from one another. A further result is the finding of an unusually strong temperature dependence in the relaxation time of the 1 molar solution of 2,6-dimethylpyridine.     

An investigation of the transformations of 2-amino-2-thiazolin-4-one and its derivatives in aqueous solutions

It has been shown by thin-layer radiochromatography that the action of an aqueous solution of alkali on 2-amino-2-thiazolin-4-one and its 5-alkyl derivatives leads predominantly to the opening of the ring by a mechanism similar to the opening of lactams in an alkaline medium.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 44–47, January 1984.     

甘氨酸从水到酰胺衍生物水溶液中的迁移焓

用RD496-Ⅱ型微量热量计测定了298.15 K甘氨酸在N-甲基甲酰胺（NMF）,N, N-二甲基甲酰胺（DMF）,N-甲基乙酰胺（NMA）,N, N-二甲基乙酰胺（DMA）水溶液中的溶解焓,计算了甘氨酸从水到四种酰胺衍生物水溶液中的迁移焓（ΔtrH）。根据结构水合作用模型讨论了酰胺的结构对甘氨酸迁移焓的影响。实验结果表明：甘氨酸在酰胺衍生物水溶液中的迁移焓均为正值,并且随着溶液浓度增大而增大。比较甘氨酸在甲酰胺（FA）和乙酰胺（AD）水溶液中的迁移焓,发现在不同酰胺水溶液中迁移焓大小为：DMA>NMA>DMF>NMF>AD>FA。甘氨酸与甲酰胺之间以亲水-亲水相互作用为主,与其它酰胺之间以亲水-疏水作用为主。     

Chitosan and its hydrophobic derivatives: Preparation and aggregation in dilute aqueous solutions

This review surveys the main methods of preparing chitosan and its hydrophobic derivatives and their influence on the microstructure of polymers. The experimental data on the aggregation of these polymers in dilute aqueous solutions are summarized. Basic factors affecting aggregation are analyzed, and its general regularities are revealed. It is shown that, in the case of both chitosan and its hydrophobic derivatives, the formation of aggregates is governed by the competition of attraction of associating groups promoting aggregation and their repulsion arising from the presence of charged units and counterions hindering aggregation. Various aggregate models that were proposed for chitosan derivatives with different main-chain lengths and different contents of associating groups are discussed.     

Photochemical polymerization of thiophene derivatives in aqueous solution

A novel method of photochemical polymerization of thiophene derivatives in aqueous solution catalyzed by potassium dichromate and initiated by illumination is described.     

Hydration numbers of glycine in aqueous sodium chloride and urea solutions

The hydration number of the glycine amino acid in aqueous sodium chloride solution is less than in aqueous urea solution; the difference increases significantly with increasing concentration of the nonaqueous component. Given the same partial volume of water, the hydration numbers of glycine in the two systems are close together (δ ≈ 5%).     

Molecular dynamics simulation of aqueous solutions of glycine betaine

Molecular dynamics simulation is used to investigate hydration properties of glycine betaine in a large range of solute concentrations. Statistical analyses of the system trajectories evidence microscopic details suggesting an interpretation of experimental results recently obtained for aqueous solutions of trimethylamine-N-oxide, a bioprotectant closely related to glycine betaine.     

Polycondensation of naphthalene and its alkyl derivatives

Polycondensation of naphthalene and its alkyl derivatives (stripping oil, 2,5-dimethylnaphthalene) in the presence of aluminum halides was performed. Under the action of an ultrasonic field on a benzene solution of naphthalene in the presence of the catalyst, intermolecular condensation and benzene addition are observed.     

Effect of temperature and ionic strength on volumetric and acoustic properties of solutions of urea alkyl derivatives in aqueous NaCl

The present work was undertaken to study volumetric and acoustic properties for diluted solutions of tetramethylurea in pure water and for urea, n-propylurea, n-butylurea and tetramethylurea in 0.5 or 1 mol · dm⁻³ aqueous solutions of sodium chloride. This paper presents measured values of densities and sound velocities at T = (288.15, 298.15 and 308.15) K. From these data the apparent molar volumes, V_Φ, adiabatic compressibilities, κ_S, and apparent molar adiabatic compressions, K_S,Φ, were obtained. The values of apparent molar volumes for infinite dilution and limited apparent adiabatic compressions were calculated from extrapolation of the concentration dependence. Further, the corresponding transfer data as well as hydration number of urea and its derivatives in the studied systems were estimated. The obtained parameters are discussed in terms of various solute-solvent and solute-cosolute interactions.     

关于苯及其衍生物在盐水溶液中的活度系数的研究

摘录了25℃时苯,甲苯,邻位、间位、对位二甲苯,间位、对位二氯苯及萘在NaF,LiCL,NaBr,NEt~4Br等25种盐的水溶液中的活度系数f,它们的lgf-c~s的关系符合Setchenow盐效应公式。计算了苯及其衍生物在上述25种盐水溶液中的各种盐效应理论的k~s,主要有:1)Debye-macAulay静电理论;2)Conway-Desnoyers-Smith静电理论;3)Masterton-Lee定标粒子理论;4)McDevit-Long内压力理论;5)改进的内压力理论;6)改进的Bockris色散力理论。对各种理论值比较后可以看到改进后的内压力理论k~s值与实验k~s值较为吻合。Bockris色散力理论经改进后计算比较简单,可以判断盐效应符号,盐效应顺序也基本正确。     

Dissolution enthalpy of glycine in aqueous solutions of bivalent metal electrolytes

Measurement of the dissolution enthalpies of glycine in aqueous solutions of MgCl₂, CaCl₂, SrCl₂, BaCl₂, Mg(NO₃)₂ and Ca(NO₃)₂ at 298.15 K have been undertaken. The enthalpic heterogeneous interaction coefficients of the glycine zwitterion with the dissociated electrolyte have been calculated using the standard enthalpies of solution of amino acid in water and in aqueous solution of electrolytes. The effect of the ion type and of the structure of glycine on the magnitude of the enthalpic interaction coefficients are discussed.     

Reduction of alkyl and aryl azides with sodium thiophosphate in aqueous solutions

A simple aqueous method for the conversion of alkyl and aryl azides into the corresponding amines using trisodium thiophosphate is presented. Thiophosphate is converted into phosphate during these formal reduction processes.     

Synthesis of new alkyl maleates ammonium derivatives and their uses in emulsion polymerization

 The synthesis of several ammonium derivatives of maleic acid diesters are reported. The starting material is the hemiester of maleic acid, easily obtained from ring opening of the maleic anhydride. The hemiester is submitted to functionalization with an aminated compound, followed by quaternari-zation with the convenient alkylation reagent. Products crystallize easily and yields are generally high. They have been fully characterized by ¹H and ¹³C NMR and the CMC have been measured. Some of them have been engaged in emulsion polymerization with styrene or methyl methacrylate. Maleates functionalized with quaternary ammonium salts yield polystyrene particle sizes around 30 nm with a narrow size distribution without adding any additional emulsifier. Received: 19 February 1996 Accepted: 17 July 1996     

Vinyl polymerization photosensitized by anthraquinone sulfonates in aqueous solutions

The kinetics of the photopolymerization of the vinyl monomers MMA and MA sensitized by anthraquinone sulfonate-NaCl-HClO₄ systems have been studied systematically. The wavelength 365 mμ was used for irradiation. Sodium anthraquinone-2-sulfonate and disodium anthraquinone-2,6-disulfonate were used as sensitizers, and all experiments were conducted in deaerated conditions. The polymerization was followed by the measurement of monomer disappearance (gravimetrically), rate of sensitizer disappearance (spectrophotometrically) and the chainlength of the polymer formed (viscometrically). Monomer concentration, k_ε, [NaCl], and I were varied. In the light of the experimental results a prima facie kinetic scheme was proposed. The specific rate constants for the various steps have been evaluated.