Organic synthesis based on cathodic deprotonation of acids

The results of studies on electrosynthesis involving carb- and heteroanions generated by cathodic deprotonation of acids (CDA), carried out in the laboratory headed by the author, are surveyed. These studies resulted in the elaboration of efficient electrochemical versions of the known Michaelis-Becker, Wittig-Horner, and Perkin reactions; electrochemical analogs of homolytic aromatic substitution, alkylation, heterocyclization,etc. were developed. Based on CDA, convenient and promising methods for preparing variousN-, O-, P-, S-, andC-alkylated and arylated substances have been developed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1411–1422, August, 1995.The author is grateful to Professor V. A. Dorokhov, Professor V. P. Litvinov, and researchers from the laboratories of N. D. Zelinsky Institute of Organic Chemistry headed by them, who participated in joint studies.The work was carried out with financial support from the International Science Foundation (Grant No. MHYOO).     

α，ω-二羧基-甲基丙烯酸丁酯低聚物的合成及MS分析

利用传统自由基聚合法，在四氢呋喃溶液中自由基引发聚合甲基丙烯酸丁酯单体而得到ω-羧基-甲基丙烯酸丁酯低聚物(CTBMA)(分子量在1500左右)；利用CTBMA末端酯基的反应特性，在二氧六环／水／KOH混合溶液中皂化CTBMA，使之转化为α，ω-羧基甲基丙烯酸丁酯低聚物(di-CTBMA)；研究了溶剂的类别、反应时间等反应条件对皂化产物结构的影响；利用MALDI-TOF-MS及LSIMS对皂化各阶段产物进行了分析监测．实验表明，在适当的皂化条件下，CTBMA皂化时主要为末端酯基转化为羧基，相应得到的产物di-CTMBA具有很好的结构特性，其官能团度(functionality)接近2．     

Hybrid organosilazane/organosilylamine telechelic oligomers—I. Two-dimensional NMR spectroscopy characterization of dimethylsilylethylenediamine oligomers

The detailed characterization of multifunctional hybrid organosilazane/organosilylamine telechelic oligomers by IR and ¹H, ¹³C and ²⁹Si NMR spectroscopy in one and two dimenions has been undertaken. The specific multifunctional oligomers, comprising NH/NH₂ or SiCl functionalities depending on the monomer feed-ratio, were prepared from mono- and di-functionally reacted dichlorodimethylsilane (DDS) and mono-, di-, tri- and tetra-functionally reacted ethylenediamine (EDA). Varying the feed-ratio afforded control of the microstructures of the oligomers and the preparation of oligomers with, in some cases, conterminously located silicon–chlorine (SiCl) groups. The combination of the NMR methods with the IR technique has enabled the detailed microstructural characterization of the oligomers and the identification of the functionalities therein. This approach and the knowledge gained from the DDS/EDA system has been applied to the microstructural characterization of other hybrid organosilazane/silylamine preceramic telechelic oligomers.     

Physico-Chemical Characterization of Yu Guo Beads(1100-771 B. C. ) in China

When was the earliest glass produced in China? This has still been a question so far. Some archaeologists have thought that Yu Guo beads are real glass, the earliest glass(1100-771 B. C. ) in China. However, more details of scientific investigations in this paper show that Yu Guo beads are mainly made of clastic quartz (>95%) with a small amount of clay and sintered under the low temperature(500-600℃). It is not a glassy body, but a kind of polycrystal ornaments.     

Study of archaeological ceramics by total-reflection X-ray fluorescence spectrometry: Semi-quantitative approach

Total-reflection X-ray fluorescence spectrometry has been compared with Instrumental Neutron Activation Analysis in order to test its potential application to the study of archaeological ceramics in the archaeometric field. Two direct solid non-chemical sample preparation procedures have been checked: solid sedimentation and solid chemical homogenization. For sedimentation procedure, total-reflection X-ray fluorescence allows the analysis of the elemental composition with respect to the size fraction but not the average evaluation of the composition. For solid chemical homogenization procedure, total-reflection X-ray fluorescence provides precise (from 0.8% to 27% of coefficient of variation) and accurate results (from 91% to 110% of recovery) for 15 elements (Cr, Hf, Ni, Rb, Al, Ba, Ca, K, Mn, Ti, V, Cu, Ga, Y and Fe) with an easy sample preparation process of the solid clay and without previous chemical treatment. The influence of the particle sizes has been checked by total-reflection X-ray fluorescence sample angle scans and anomalous behaviors have been found for three additional detected elements: As, Sr and Zn, which can be attributed to interference effects of the mineral grain sizes of their associated chemical phases in the total-reflection X-ray fluorescence interference region. The solid chemical homogenization procedure produces data useful for archaeological interpretation, which is briefly illustrated by a case-study. Finally, the decantation procedure data can be also useful for size chemical speciation and, consequently, for alternative environmental total-reflection X-ray fluorescence applications.     

Thermal and chemical nanofractal relaxation

We studied shape relaxation of nano-fractal islands, during annealing, after their growth from antimony cluster deposition on graphite surface. Annealing at 180^°C shows evidence of an increase of the fractal branch width with time followed by branch fragmentation, without changing the fractal dimension. The time evolution of the width of the arm suggests the surface self-diffusion mechanism as the main relaxation process. With Monte Carlo simulations, we confirmed the observed behavior. Comparison is done with our previous results on fragmentation of nano-fractal silver islands when impurity added to the incident cluster promotes rapid fragmentation by surface self-diffusion enhancement [1].     

Study of intermediates formed in the oxidation of thiols

The oxidation of aminoethanethiol (1) was investigated in acid solutions on a glass carbon anode. It was shown that at relatively low anode potentials thiyl radicals RS^· are released into the solution, but this does not lead to binding of the oxygen in the solution. Raising the anode potential leads to binding of oxygen, which is probably due to the formation of the intermediate RS⁺. The oxidation of 1 was studied in Ce(SO₄)₂+H₂SO₄ solution. It was shown that under certain conditions the intermediate is RS⁺, which subsequently converts to a product that could not be identified as any previously described product of the oxidation of thiols. Proposals are made regarding its structure and conversion pathways.B. P. Konstantinov Institute of Nuclear Physics, Russian Academy of Sciences, 188350 Leningrad. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 278–288, February, 1992.     

杀菌剂福美双的电化学性质及线性扫描溶出伏安法测定

提出了线性扫描溶出伏安法测定福美双的电分析化学方法.在 pH 5.0 HAc-NaAc缓冲溶液中福美双在汞电极上出现一还原峰,峰电位为-610 mV(vs.Ag/AgCl).采用各种电化学技术如循环伏安法和线性扫描溶出伏安法等对本体系进行研究,发现采用线性扫描溶出伏安法能得到较灵敏的还原峰,呈现不可逆电极反应现象,并具有一定的吸附性,在210 s时能达到吸附平衡.选择吸附时间为180 s时,线性范围为0.02～0.14 μg·mL-1,最低检测限为9.5 ng·mL-1.将本方法用于实际样品的测定,得到满意的结果.     

Electrochemical co-oxidation of C-H acids and methanol as a new route to functionalized cyclopropanes

Electrolysis of dimethyl malonate or methyl cyanoacetate in methanol in the presence of LiCl in an undivided cell leads to formation of 1,1,2,2-cyclopropanetetracarboxylic derivatives.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1835–1836, October, 1994.This work was supported by the International Science Foundation (Grant No MHY 000).