OH-Induced shift from carbon to oxygen acidity in the side-chain deprotonation of 2-, 3- and 4-methoxybenzyl alcohol radical cations in aqueous solution: results from pulse radiolysis and DFT calculations

DFT calculations have been carried out for 2-, 3- and 4-methoxybenzyl alcohol radical cations (1⁺, 3⁺ and 4⁺, respectively) and the α-methyl derivatives 2⁺ and 5⁺ using the UB3LYP/6-31G(d) method. The theoretical results have been compared with the experimental rate constants for deprotonation of 1⁺-5⁺ under acidic and basic conditions. In acidic solution, the decay of 1⁺-5⁺ proceeds by cleavage of the C-H bond, while in the presence of ⁻OH all the radical cations undergo deprotonation from the α-OH group. This pH-dependent change in mechanism has been interpreted qualitatively in terms of simple frontier molecular orbital theory. The ⁻OH induced α-O-H deprotonation is consistent with a charge controlled reaction, whereas the C-H deprotonation, observed when the base is H₂O, appears to be affected by frontier orbital interactions.     

On the self-association of the normal alcohols and the glass transition in alcohol-alcohol solutions

The glass-transition temperature (T_g) in mutual binary mixtures of the primary alkanols from methanol throughn-octanol has been measured as a function of composition. For mixtures of the alkanols heavier than ethanol,T _g is found to be a linear function of the number-average molecular length. Methanol and ethanol mixtures show higherT _g values than indicated by this relation. These results are found to be consistent with association of the heavier alkanols into chains of very great length in the supercooled liquid, while ethanol and methanol must form networks with a moderate degree of crosslinking between chains.     

Ligand creation via linking—a rapid and convenient method for construction of novel supported PyOX-ligands

A novel supported amino alcohol linker was synthesized and utilized for attachment of picolinic acid derivatives onto different supports. When the resin bound molecule was further activated, the PyOX-moiety could be constructed reliably in enantiopure form. Furthermore, an efficient Pd-catalyzed modification of a picolinic acid derivative is presented.     

Ethyl α-cyanoacrylate in the Michael reaction

Ethyl -cyanocarylate undergoes the Michael reaction with strong CH-acids (pK _a < 13) in the presence of strong basic amines such as butylamine, piperidine, and triethylamine. Only polymerization of ethyl -cyanoacrylate occurs under the same conditions with weaker CH-acids in the presence of less basic amines such as aniline, N-methylaniline, and pyridine.A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2449–2452, October, 1992.     

Synthesis and investigation of mono- and binuclear cyano-bridged complexes of rhodium,ruthenium, and palladium

Binuclear Rh^III and Ru^II complexes of the [M¹-CN-M²]⁺BF ₄ ^– (M¹ and/or M² are (⁵-Cp)(³-C₃H₅)Rh and (⁶-C₆H₆)(³-C₃H₅)Ru) type, heteronuclear organometallic compound (⁵-Cp)(³-C₃H₅)RhCNPd(³-C₃H₅)Cl, and mononuclear Rh^III and Ru^II complexes [(³-C₃H₅)LM(MeCN)]⁺ _BF4 ^– (M = Rh, L = ⁵-Cp; M = Ru, L = ⁶-C₆H₆) were synthesized. An electrochemical study of these compounds in solutions demonstrates that the bond between the bridged CN ligand and the metal atoms is rather strong, and there is no dissociation into mononuclear fragments in solutions. The kinetics of the reaction of [(⁵-Cp)(³-C₃H₅)Rh(MeCN)]⁺ _BF4 ^– with halide ions was studied by electrochemical methods. The ligand exchange proceeds by a bimolecular dissociative-exchange mechanism.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 968–973, May, 1995.     

4-咪唑甲酸乙酯的制备

甘氨酸经乙酰化、酯化，在氢化钠作用下与甲酸乙酯缩合，然后在盐酸条件下与硫氰酸钾关环，最后通过双氧水氧化脱巯基，得到咪唑甲酸乙酯，总产率为13％．产物经核磁、元素分析表征．     

聚丙烯酸乙酯-g-聚甲基丙烯酸甲酯接枝共聚物的合成

丙烯酸乙酯与2-溴丙烯酸乙酯乳液共聚合制备了聚(丙烯酸乙酯-co-2-溴丙烯酸乙酯)无规共聚物，用该共聚物作为原子转移自由基聚合的大分子引发剂，进行了甲基丙烯酸甲酯的接枝聚合，制备了聚丙烯酸乙酯-g-聚甲基丙烯酸甲酯接枝共聚物。接枝共聚物的分子量随单体转化率的上升而线性增加。     

Effect of Carboxymethyl Starch as Stabilizer for Increasing the Stability of Warp Sizing Pastes

The influences of carboxymethyl starch used as stabilizer upon the stability of native cornstarch-polyvinyl alcohol blend pastes for warp sizing have been investigated. The effect of the modified starch on the paste stability was evaluated in terms of the initial demixing time and the volume percentage of separated starch. The carboxymethyl starch with a series of different degrees of substitution was prepared in ethanol dispersion by varying the amount of monochloroacetic acid reacted with refined native cornstarch. The paste stability strongly depends on the modification extent and amount of carboxymethyl starch used, and on native starch content in the paste. Increase in the modification extent and/or the amount of the modified starch effectively retards the phase separation and reduces the separation extent of native cornstarch-polyvinyl alcohol blend pastes. Moreover, the mechanism and favorable modification extent of carboxymethyl starch for enhancing paste stability are also investigated and disc     

泽泻中三萜醇酮类化合物总量的快速测定方法研究

建立了利用便携式小型光谱仪测定中药泽泻中三萜醇酮类化合物总量的比色测定方法.本方法采用具有C 3羰基的甾酮类化合物的专属性Zimmerman显色反应,检测波长为560nm.以23 乙酰泽泻醇B的吸光度和浓度作工作曲线,回归方程为A=2.1009C+0.2116(mg/mL),相关系数为0.9997,23 乙酰泽泻醇B的浓度在0～160mg/mL范围内符合比耳定律,表观摩尔吸收系数ε=5.4×102L·mol-1·cm-1,检出限为11.143mg/mL,回收率为93.0%～109%.该方法简单、快速、廉价,已成功应用于福建地道药材泽泻GAP过程质量控制及泽泻药材品质的评价,指导泽泻药材的生产,具有重大的经济效益和社会意义.     

酸性醇溶液提取魔芋中的总生物碱研究

研究了用酸性醇溶液回流法提取魔芋中总生物碱的方法和条件．结果表明，提取魔芋中总生物碱较佳的工艺条件是：在pH值为2～3的酸性醇溶液中，回流提取3h，总生物碱的含量可达0.39％.