Thermodynamic dissociation constants of salicylic and monochloroacetic acids in mixed solvent systems from conductance measurements at 25°C

The molar conductances of dilute solutions of salicylic and monochloroacetic acids in binary mixtures of methanol, ethanol, 1-propanol, N,N-dimethylformamide, acetone, acetonitrile, tetrahydrofuran and dioxane with water have been measured at 25°C. The Lee-Wheaton conductance equation was fitted to the data in order to derive thermodynamic dissociation constants and limiting molar conductances. The results were compared with those in the literature pertaining to analogous media, mostly derived potentiometrically. The findings are interpreted in terms of a solvent effect on the ionization of these acids in mixed solvent systems.This paper is dedicated to the late Professor Raymond M. Fuoss on his 3^rd anniversary.     

Thermal and spectroscopic investigations of new lanthanide complexes with 1,2,4-benzenetricarboxylic acid

The new 1,2,4-benzenetricarboxylates of lanthanide(III) of the formula Ln(btc)·nH₂O, where btc is 1,2,4-benzenetricarboxylate; Ln is La-Lu, and n=2 for Ce; n=3 for La, Yb, Lu; and n=4 for Pr-Tm were prepared and characterized by elemental analysis, infrared spectra and X-ray diffraction patterns. Polycrystalline complexes are isotructural in the two groups: La-Tm and Yb, Lu. IR spectra of the complexes show that all carboxylate groups from 1,2,4-benzentricarboxylate ligands are engaged in coordination of lanthanide atoms. The thermal analysis of the investigated complexes in air atmosphere was carried out by means of simultaneous TG-DTA technique. The complexes are stable up to about 30°C but further heating leads to stepwise dehydration. Next, anhydrous complexes decompose to corresponding oxides. The combined TG-FTIR technique was employed to study of decomposition pathway of the investigated complexes.     

乙醇在杂多酸上的氧化、脱水和程序升温脱附研究

合成了两个系列具有Keggin结构的12-钒钼磷酸和钨钼磷酸,研究了它们对乙醇氧化、脱水的催化反应。借助程序升温脱附技术研究了反应物及产物乙醇、乙烯、乙醚等在样品上的程脱作用。讨论了钨、钒取代部分钼原于后对杂多酸酸性及氧化性能的影响。     

Excess molar enthalpies of binary mixtures for (tributyl phosphate+methanol/ethanol) at 298.15 K

Excess molar enthalpies of binary mixtures for tributyl phosphate (TBP)+methanol/ethanol were measured with a TAM air Isothermal calorimeter at 298.15 K and ambient. The results for xTBP+(1–x)CH₃OH are negative in the whole range of composition, while the values for xTBP+(1–x)C₂H₅OH change from positive values at low x to small negative values at high x. The experimental results have been correlated with the Redlich–Kister polynomial. IR spectra of the mixtures were measured to investigate the effect of hydrogen bonding in the mixture.     

Orifluoroacetylation and dehydration of 20-hydroxyecdysone acetonides. Synthesis of stachisterone B

Orifluoroacetylation of the 25(OH)-group with subsequent dehydration of the 14(OH)-group takes place in the reaction of 20-hydroxyecdysone 20,22-acetonide and 2,3:20,22-diacetonide with trifluoroacetic anhydride in the presence of pyridine. Dehydration of the 14(OH)-group gives rise to stachisterone B derivatives, which are hydrolyzed to give the phytoecdysteroid stachisterone B.     

Selection of thermotolerant yeasts for simultaneous saccharification and fermentation (SSF) of cellulose to ethanol

A total of 27 yeast strains belonging to the groupsCandida, Saccharomyces, andKluyveromyces were screened for their ability to grow and ferment glucose at temperatures ranging 32-45°C. K. marxianus andK. fragilis were found to be the best ethanol producing organisms at the higher temperature tested and, so, were selected for subsequent simultaneous saccharification and fermentation (SSF) studies.     

Kinetic parameters of unsaturated polyester resin modified with poly(ε -caprolactone)

The mineral sabugalite (HAl)_0.5[(UO₂)₂(PO₄)]₂⋅8H₂O, has been studied using a combination of energy dispersive X-ray analysis, X-ray diffraction, dynamic and controlled rate thermal analysis techniques. X-ray diffraction shows that the starting material in the thermal decomposition is sabugalite and the product of the thermal treatment is a mixture of aluminium and uranyl phosphates. Four mass loss steps are observed for the dehydration of sabugalite at 48°C (temperature range 39 to 59°C), 84°C (temperature range 59 to 109°C), 127°C (temperature range 109 to 165°C) and around 270°C (temperature range 175 to 525°C) with mass losses of 2.8, 6.5, 2.3 and 4.4%, respectively, making a total mass loss of water of 16.0%. In the CRTA experiment mass loss stages were found at 60, 97, 140 and 270°C which correspond to four dehydration steps involving the loss of 2, 6, 6 and 2 moles of water. These mass losses result in the formation of four phases namely meta(I)sabugalite, meta(II)sabugalite, meta(III)sabugalite and finally uranyl phosphate and alumina phosphates. The use of a combination of dynamic and controlled rate thermal analysis techniques enabled a definitive study of the thermal decomposition of sabugalite. While the temperature ranges and the mass losses vary due to the different experimental conditions, the results of the CRTA analysis should be considered as standard data due to the quasi-equilibrium nature of the thermal decomposition process. The online version of the original article can be found at     

氯铝酸室温离子液体介质中正碳十二烯选择环化反应

 在氯化1－丙基－3－甲基咪唑（PMImCl）、氯化1－丁基－3－甲\r\n基咪唑（BMImCl）、氯化1－丁基吡啶（BPCl）和溴化1－乙基吡啶（E\r\nPBr）季铵盐与AlCl3构成的室温离子液体介质中，首次发现正十二碳烯\r\n（简称十二烯）可以高选择性地发生环化反应生成环十二烷．依次在反\r\n应管中加入氯铝酸室温离子液体、乙醇和十二烯，其中AlCl3的量为0．\r\n01mol，AlCl3与季铵盐的摩尔比为2，乙醇为10ml，十二烯为2ml（9．\r\n3mmol）．当反应体系中不添加乙醇时，十二烯转化率和环十二烷选择\r\n性仅分别为4．2％和73．1％．这是由于十二烯和氯铝酸离子液体形成\r\n两相体系而不易充分接触，故十二烯转化率和环十二烷选择性较低．当\r\n反应体系中加入乙醇时，十二烯和氯铝酸离子液体体系变为单相，使得\r\n十二烯和氯铝酸离子液体可以充分接触，十二烯转化率和环十二烷选择\r\n性可分别达到12．4％和82．9％．压力对提高十二烯转化率和环十二烷\r\n选择性有很大的影响．p（N2）＝3．0～6．0MPa下反应12h，十二烯转\r\n化率和环十二烷选择性可分别达到27．2％和93．8％．反应结束后加热\r\n除去乙醇，产物自动与离子液体分层，便于分离，且离子液体介质可重\r\n复使用．     

铝交联皂石的合成和表征及催化性能

用XRD、化学分析、IR、MASNMR、TPD等手段表征了合成皂石及其铝交联物的结构。结果表明:皂石的交联密度与四面体层电荷和交联条件(Al/土比)有关。在乙醇氨化反应中,交联皂石显示了较好的催化活性和选择性。皂石的交联密度与液相产物分布的关系表明层柱材料对此反应具有择形催化作用。醇氨化反应可能是在吸附态NH_3和气相醇分子间进行的。