Synthesis of substituted pyrido[1,2-<Emphasis Type="Italic">a</Emphasis>]pyrimidines from 2-arylmethylidene-3-fluoroalkyl-3-oxopropionates

Cyclocondensation of 2-arylmethylidene-3-fluoroalkyl-oxopropionates with 2-amino-pyridine occurs at both the polyfluoroacylvinyl and alkoxycarbonylvinyl fragments to give alkyl 4-aryl-2-polyfluoroalkyl-4H-pyrido[1,2-a]pyrimidine-3-carboxylates and 4-aryl-2-hydroxy-3-polyfluoroacyl-4H-pyrido[1,2-a]pyrimidines, respectively. When treated with copper(II) acetate, the pyrido[1,2-a]pyrimidines yield metal complexes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2745–2749, December, 2005.     

Thermochemistry of aromatic ketones. Experimental enthalpies of formation and structural effects

The standard enthalpies of formation Δ_fH^o (liq. or cr.) at the temperature T = 298.15 K were measured using combustion calorimetry for benzophenone (A), 1-indanone (B), -tetralone (C), 9-fluorenone (D), anthrone (E) and dibenzosuberone (F). The standard enthalpies of vaporization Δ_vH^o or sublimation Δ_sH^o of A-F and 5,7-dihydro-6H-dibenzo[a,c]cyclohepten-6-one (G) were obtained from the temperature function of the vapor pressure measured in a flow system. Enthalpies of fusion Δ_mH of solid compounds were measured by DSC. From the enthalpies of formation of the gaseous compounds of A-G the values of their strain enthalpies were derived and structural effects discussed.

     

MH—Ni电池封口化成及其性能

在硼氢化钾碱性溶液中对金属氢化物（ＭＨ）电极的表面进行化学还原处理，提高了ＭＨ电极的放电容量、活化性能和电催化活性．用其为负极组装的ＡＡ型ＭＨ－Ｎｉ电池进行了封口化成，电池放电容量达到１１５０ｍＡｈ，５Ｃ下电池的放电容量达到０．２Ｃ下容量的８０％以上，电池在１Ｃ１００％ＤＯＤ（放电深度）充放电条件下，循环寿命由原来的１００次左右提高到２００次以上     

Phase separation of poly(γ-benzyl L-glutamate) to liquid crystal and isotropic solution in various helicogenic solvents

Solvent effects on the phase separation of poly(-benzyl L-glutamate) to liquid crystal and isotropic solution have been observed in various helicogenic solvents. The temperature-composition phase diagrams have been determined for each solution. The critical concentrations, ₂ ^* , at which the phase separation occours have been compared in various solvents. In dimethylformamide in which the polymer is molecularly dispersed, the observed ₂ ^* value has agreed with that calculated by Flory's theory. In some solvents in which the polymer aggregates in a head-to-tail mode such as chloroform, the observed ₂ ^* values have been considerably small. It is assumed that the polymer aggregates behave as longer particles than the original particles. In dioxane in which the polymer aggregates highly both in a head-to-tail and a side-by-side modes, the ₂ ^* value has been a little larger than that in chloroform. In this case the relationship between the aggregation and the liquid crystal formation is so complicated that further investigation is necessary. In aromatic solvents such asm-cresol that dissolves the polymer almost molecularly, the ₂ ^* is smaller than that in dimethylformamide. Therefore, the intermolecular interactions between the phenyl groups in the side groups of the polymer and those in solvent molecules must be considered.The author is grateful to Mr. K. Sano and Mr. M. Watanabe for their observation of the liquid crystal formation.     

Solid-solute phase equilibria in aqueous solution. VI. Solubilities,complex formation,and ion-interaction parameters for the system Na+−Mg2+−ClO 4 − −CO2−H2O at 25°C

The stoichiometric solubility constant of eitelite (NaMg _0.5 CO ₃ +2H⁺ ⇄ Na⁺+0.5Mg ²⁺ +CO ₂ (g)+H ₂ O, log^*K _pso ^I =14.67±0.03 was determined at I=3 m (mol kg⁻¹) (NaClO ₄ ) and 25°C. The stability of magnesium (hydrogen-)carbonato complexes in this ionic medium was explicitely taken into account. Consequently, trace activity coefficients of free ionic species, calculated from the Pitzer model with ion-interaction parameters from the literature, were sufficient for an evaluation of the thermodynamic solubility constants and Gibbs energies of formation for eitelite (−1039.88±0.60), magnesite (−1033.60±0.40), hydromagnesite (−1174.30±0.50), nesquehonite (−1724.67±0.40), and brucite (−835.90±0.80 kJ-mol ⁻¹ ). The increasing solubilities of nesquehonite and eitelite at higher sodium carbonate molalities were explained by invoking a magnesium dicarbonato complex (Mg²⁺+2CO ₃ ²⁻ ⇄ Mg(CO₃) ₂ ²⁻ , log β_z = 3.90 ± 0.08). A set of ion-interaction parameters was obtained from solubility and dissociation constants for carbonic acid in 1 to 3.5 m NaClO ₄ media which reproduce these constants to 0.02 units in log K. The following Pitzer parameters are consistent with the previously studied formation of magnesium (hydrogen-)carbonato complexes in 3m NaClO ₄ . The model and Gibbs functions of solid phases derived here reproduce original solubility data (−log [H⁺], [Mg ²⁺ ] _tot ) measured in perchlorate medium within experimental uncertainty. Presented at the XXII International Conference on Solution Chemistry, July 14–19, 1991, Linz, Austria.     

Effect of arrangement of the styryl fragment on the optical properties and complexation of mono-and bis(styryl)-substituted <Emphasis Type="Italic">N</Emphasis>-methylpyridinium perchlorates containing benzo-15-crown-5 ether moieties

Using ¹H NMR spectroscopy and steady-state and time-resolved electronic spectroscopy, the optical properties of mono-and bis(styryl)pyridinium perchlorates and their complexes with Mg²⁺, Ba²⁺ cations were studied. The stability constants of the complexes were determined using spectrophotometric titration. The formation of inclusion complexes for Mg²⁺ and sandwich type complexes for Ba²⁺ results in fluorescence enhancement and increases the lifetimes of the excited states of the initial bis-styryl ligands. The variation of position of the styryl fragment in the pyridinium aromatic ring gives rise to photochromic crown ethers with different optical and photophysical characteristics and is also an easy route to bis(crown-ethers) of symmetrical and unsymmetrical structure. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2092–2100, November, 2007.     

钯催化下有机锡化合物的偶联反应在碳-碳键形成过程中的应用

本文述评了最近几年来钯催化的有机锡化合物与有机亲电试剂的交叉偶联反应在有机合成中用于碳-碳键形成的主要研究成果。主要讨论了直接交叉偶联反应,CO或烯键插入的交叉偶联反应和机理。     

Phase-transfer catalytic activity of soluble polystyrenes containing crown ether moieties and hydroxyl groups adjacent to the macrorings

Soluble polystyrenes with crown ether structures and hydroxyl groups adjacent to the macrorings were prepared by the reaction of epoxide-containing polystyrenes with monoaza-15-crown-5 or monoaza-18-crown-6. Rate of formation of the polymer-bound alkali cation-crown alkoxide ion pair from the soluble polystyrenes and aqueous NaOH or KOH depended on the loading of crown ether and hydroxyl units and on the size of the macroring. The elimination of HCl from less reactive 2-chloroethylbenzene with aqueous NaOH or KOH in the presence of the soluble polystyrene catalysts under two-phase conditions was limited mainly by the intrinsic reaction rate. The elimination of HBr from more reactive 2-bromoethylbenzene in the presence of the less (11%) ring-substituted polymer catalyst with 18-crown unit was limited by the alkoxide formation rate. © 1994 John Wiley & Sons, Inc.     

Comments on the primary and scatter dose-spread kernels used for convolution methods

The basic primary and scatter dose-spread kernels used for convolution methods are usually produced by Monte Carlo simulations with the interaction point forced to the center of a large water phantom. However, it is still not clear whether such Monte Carlo based kernels allow accurate dose calculations with a wide range of field sizes and depths, especially in thorax phantoms. Using the differential primary and scatter concept, this paper proposes another type of basic kernel, with which perfectly accurate primary and scatter absorbed dose calculations can be performed under conditions that the beam is parallel, the incident beam intensity is uniform within and zero outside the field, and the primary beam attenuation coefficient along raylines is not a function of depth and off-axis distance.     

Dispersion polymerization of methyl methacrylate: Mechanism of particle formation

The mechanism for the formation of micron-size polymer particles in the dispersion polymerization of methyl methacrylate was investigated by applying dynamic light scattering to monitor the evolution of the average particle size in the early stages of the polymerization. In addition, the contributions of physically adsorbed stabilizer and graft copolymer were evaluated by measuring the bound, unbound (adsorbed), and free stabilizer, and by determining the amount of added stabilizer required in seeded dispersion polymerizations. Twenty nanometer particles (termed nuclei) were the smallest particles detected and are considered to be formed by aggregation of growing polymer chains precipitating from solution as they exceed their critical chain length. Aggregation of these nuclei with themselves and their aggregates continues until mature and stable particles are formed. This occurs when sufficient stabilizer occupies the particle surface which includes both the polymeric stabilizer [poly(vinylpyrrolidone)] and its graft copolymer which is created in situ. The effects of process variables are discussed based on this mechanistic picture of the dispersion polymerization process. © 1994 John Wiley & Sons, Inc.