Inhibition ability of ionic liquid [Bmim][NO3], [Bmim][BF4], and [Emim][BF4] on spontaneous coal combustion

Journal of Thermal Analysis and Calorimetry - From TG result, [Bmim][BF4] has the best inhibition ability of spontaneous coal combustion to delay the initial temperature, maximum temperature, and...     

Thermodynamic Properties of Binary Mixtures of the Amino Acid Ionic Liquids [Bmim][Glu] or [Bmim][Gly] with Methanol at T=298.15 to 313.15 K

Densities, viscosities and refractive indices were determined for two ionic liquid mixtures formed by the 1-butyl-3-methylimidazolium glutamic acid salt ([Bmim][Glu]) or the 1-butyl-3-methylimidazolium glycine acid salt ([Bmim][Gly]), respectively, with methanol over the mole fraction from 0.1 to 0.9 and at temperatures ranging from 298.15 K to 313.15 K at intervals of 5 K and at atmospheric pressure. Excess molar volumes, viscosity deviations and refractive index deviations have been calculated from the experimental data and fitted to a Redlich–Kister polynomial function. The results have been interpreted in terms of ion-dipole interactions, and structural factors of the ionic liquid and alcohol molecular liquids.     

Reactions of methylcyclohexanones with concentrated sulfuric acid

Conclusions In reaction with concentrated sulfuric acid 2-, 3-, and 4-methylcyclohexanones undergo autocondensation and simultaneous intramolecular cyclization with formation of furan compounds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 1958–1963, November, 1966.     

Reaction of cycloheptanone with concentrated sulfuric acid

Treatment of cycloheptanone or 2-cycloheptylidenecycloheptanone with concentrated sulfuric acid, leads to self-condensation accompanied by intramolecular rearrangement and cyclization to give substituted tetrahydrofurans, viz. 2-methyl-2, 3-cyclohexano-4, 5-cyclohepteno-(⁵)-2, 3, 4, 5-tetrahydrofuran and 2-methyl-2, 3-cyclohexano-5-hydroxy-4, 5-cycloheptano-2, 3, 4, 5-tetrahydrofuran. Self-condensation of ketones with 6-membered rings under the action of concentrated sulfuric acid, proceeding via carbonium ions, and accompanied by contraction to a 5-membered ring, is also characteristic of cycloheptanone, the 7-membered ring of which isomerizes to a 6-membered one.     

A sensor for the in situ determination of acidity levels in concentrated sulfuric acid

A potentiometric method at imposed weak current between two paste electrodes, ferrocene and chloranil, permits the in situ determination of sulfuric acid concentrations (0.5–11.0 M). The different factors affecting the potential at imposed current as current intensity, temperature and H⁺ ion concentration are studied. The potentials measured between ferrocene and chloranil electrodes are directly linked to the acid concentration. The acidity R_i(H) function, which represents the determination of the H⁺ activity has been determined and compared to Strehlow R_o(H), Janata H_GF and Hammet H_o functions. R_i(H) is numerically equal to the thermodynamic R_o(H). Received: 19 October 1998 / Revised: 22 March 1999 / Accepted: 23 March 1999     

Transformations of substituted tetrahydro-8h-indeno[1,2-d]imidazoles in concentrated sulfuric acid

The five-membered ring of the indene system in 2,8-dioxo-3a-hydroxy-8a-R-1,2,3a,8a-tetrahydro-8H-indeno[1,2-d]imidazoles is hydrolytically cleaved in concentrated sulfuric acid solutions. Depending on the reaction conditions, compounds for which substituted 4-(o-carboxyphenyl)imidazol-2-one (II), 1,8-dioxo-1,2-dihydro-8H-imidazo[4,3-a]isoindole (III), and spiro[imidazolidine-4,3′-phthalide] structures were assumed were isolated.     

A sensor for the in situ determination of acidity levels in concentrated sulfuric acid

A potentiometric method at imposed weak current between two paste electrodes, ferrocene and chloranil, permits the in situ determination of sulfuric acid concentrations (0.5–11.0 M). The different factors affecting the potential at imposed current as current intensity, temperature and H⁺ ion concentration are studied. The potentials measured between ferrocene and chloranil electrodes are directly linked to the acid concentration. The acidity R_i(H) function, which represents the determination of the H⁺ activity has been determined and compared to Strehlow R_o(H), Janata H_GF and Hammet H_o functions. R_i(H) is numerically equal to the thermodynamic R_o(H). Received: 19 October 1998 / Revised: 22 March 1999 / Accepted: 23 March 1999     

Unstable Supramolecular Structure of [Bmim][BF4] in Aqueous Solution

To unravel the exact composition and structure of aggregates in an aqueous solution of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF₄]), we performed static and dynamic light-scattering measurements, as well as transmission electron microscopy (TEM). Results from this work show that the aggregates are vesicles and unstable; herein, we discuss the driving force behind the self-assembly. Apart from the van der Waals forces and repulsive electrostatic interactions between adjacent cation clusters, the hydrogen-bonding forces as well as counterion effects might also contribute to this driving force. The information obtained here is useful for a better understanding of the vital role that aggregation behavior plays in the field of ionic liquid recovery, and its potential use in controlled release, drug delivery, and petroleum recovery.     

Thermodynamic studies of ionic interactions in aqueous solutions of imidazolium-based ionic liquids [Emim][Br] and [Bmim][Cl

Experimental measurements of density at different temperatures ranging from 293.15 to 313.15 K, the speed of sound and osmotic coefficients at 298.15 K for aqueous solution of 1-ethyl-3-methylimidazolium bromide ([Emim][Br]), and osmotic coefficients at 298.15 K for aqueous solutions of 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]) in the dilute concentration region are taken. The data are used to obtain compressibilities, expansivity, apparent and limiting molar properties, internal pressure, activity, and activity coefficients for [Emim][Br] in aqueous solutions. Experimental activity coefficient data are compared with that obtained from Debye-Hückel and Pitzer models. The activity data are further used to obtain the hydration number and the osmotic second virial coefficients of ionic liquids. Partial molar entropies of [Bmim][Cl] are also obtained using the free-energy and enthalpy data. The distance of the closest approach of ions is estimated using the activity data for ILs in aqueous solutions and is compared with that of X-ray data analysis in the solid phase. The measured data show that the concentration dependence for aqueous solutions of [Emim][Br] can be accounted for in terms of the hydrophobic hydration of ions and that this IL exhibits Coulombic interactions as well as hydrophobic hydration for both the cations and anions. The small hydration numbers for the studied ILs indicate that the low charge density of cations and their hydrophobic nature is responsible for the formation of the water-structure-enforced ion pairs.     

Solubility of selected dibasic carboxylic acids in water,in ionic liquid of [Bmim][BF4], and in aqueous [Bmim][BF4] solutions

The solubilities of three dibasic carboxylic acids (adipic acid, glutaric acid, and succinic acid) in water, in the ionic liquid of 1-butyl-3-methyl-imidazolim tetrafluoroborate ([Bmim][BF₄]), and in the aqueous [Bmim][BF₄] solutions have been measured by a solid-disapperance method. The binodal curve of water + [Bmim][BF₄] was also determined experimentally from solid–liquid–liquid coexistence temperature up to near the upper critical solution temperature. Experimental results showed that each acid-containing binary behaved as a simple eutectic system. The solid–liquid equilibrium (SLE) data were correlated with the NRTL model for each binary system. The NRTL model with these determined binary parameters predicted the solid-disappearance temperatures of the aqueous ternary mixtures containing [Bmim][BF₄] and the dibasic acids to within an average absolute deviation of 2.0%.     

离子液体[Bmim][BF_4]中卟啉的三线态动力学

室温离子液体由于其几乎不挥发、稳定性突出、良好的电化学性能以及结构与性能的可设计性等优点,在诸多领域得到了深入的研究和广泛的应用。与传统的普通溶剂不同,离子液体的本质特点之一是其内部的微观结构具有微不均匀性。本文通过对四苯基卟啉(TPP)分子在离子液体[Bmim][BF_4]中的三线态动力学研究,发现在激光作用下,TPP的三线态寿命由2.95μs显著增加到184μs。进一步分析表明,这一现象很可能是由于离子液体的微结构在激光诱导下发生变化,被激光场或者离子诱导极化的氧气分子在离子液体微不均匀性环境中发生重新分布而引起的。     

Difunctional effects of [Bmim][DBP] on curing process and flame retardancy of epoxy resin

Journal of Thermal Analysis and Calorimetry - To optimize the curing process and improve the flame retardancy of epoxy resin, 1-butyl-3-methylimidazolium dibutyl phosphate ([Bmim][DBP]) was used as...     

离子液体[bmim][PF6]与[moemim][PF6]结构微不均匀性以及微粘度的光谱探测

室温离子液体由于其极低的蒸汽压、比较好的热稳定性和化学稳定性、良好的分子结构与性能的可设计性等优点,作为一种新型的环境友好溶剂在很多领域有着广泛的应用.对于离子液体的微观结构和微观性能的研究是设计新型离子液体以及扩展离子液体应用的关键.本文通过荧光探针分子香豆素153(C153)的转动动力学和对微观环境敏感的荧光探针分子1, 3-二(1-芘基)丙烷(BPP)的稳态荧光光谱,探测和表征了烷基取代的离子液体1-丁基-3-甲基咪唑六氟磷酸盐([bmim][PF₆])和与其具有相似结构的醚键官能化的离子液体1-甲氧基乙基-3-甲基咪唑六氟磷酸盐([moemim][PF₆])的微观结构和微粘度. C153探针分子在离子液体[bmim][PF₆]中的转动过程具有快、慢两个组分表明离子液体[bmim][PF₆]内部存在松散和紧密的两种结构微区;而C153探针分子在离子液体[moemim][PF₆]中的转动动力学只存在一种过程,说明醚键的引入使得[moemim][PF₆]内部趋于一种类型的微环境.通过C153探针分子的转动时间研究发现,醚键官能化的离子液体[moemim][PF₆]的微粘度小于烷基链取代的离子液体[bmim][PF₆],同时通过BPP探针分子的二聚体激基复合物(excimer)与单体(monomer)荧光发射强度的比值(I_E/I_M)研究也证明这一结果.醚键的引入使得离子液体[moemim][PF₆]相对于离子液体[bmim][PF₆],侧链的极性更大、柔顺性更好,同时醚键有可能作为氢键的受体与阳离子形成氢键从而削弱离子液体中阴、阳离子间的相互作用,使得离子液体[moemim][PF₆]的微观环境比离子液体[bmim][PF₆]更为均一,同时具有更小的微粘度.     

Synthesis of novel imidazo[1,2-a][3,1]benzothiazines 4, imidazo[1,2-a]-[1,2,4]benzotriazines 5, and 4H-imidazo[2,3-c]pyrido[2,3-e][1,4]oxazines 6

Starting from the readily available 2-aminobenzhydrols ( 7 ), 3-amino-1,2,4-benzotriazine ( 11 ) and 2-amino-3-pyridinol ( 12 ), novel derivatives of 5-phenyl-5H-imidazo[1,2-a][3,1]benzothiazine-2-carboxylic acid, ethyl ester ( 4 ), imidazo[2,1-c][1,2,4]benzotriazine-2-carboxylic acid, ethyl ester ( 5 ) and 4H-imidazo[2,3-c]pyrido-[2,3-e][1,4]oxazine ( 6 ) were prepared.     

Spectrophotometry of glycosides of oleanolic acid and hederagenin in concentrated sulfuric acid

Summary The UV spectra in concentrated sulfuric acid of hederagenin and oleanolic acid and their glycosides has been studied. For analytical purposes it is proposed to use the extremum at a wavelength of 405 nm, which is distinguished by constancy of position and intensity of absorption for the genins and their glycosides.A spectrophotometric method is proposed for the determination of the triterpene glycosides in a preparation from the bulbs ofLeontice ewersmannii Bge.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 220–227, March–April, 1977.     

[Bmim]Br3对酮的选择性单溴化反应

在无溶剂和室温条件下, 三溴化1-丁基-3-甲基咪唑([Bmim]Br₃)选择性地与酮反应, 以90%～96%的产率生成相应的α-溴代酮. 该方法反应条件温和、产率高、选择性好、环境友好.