Isothermal vapour–liquid equilibria in the ternary system tert-butyl methyl ether + tert-butanol + 2,2,4-trimethylpentane and the three binary subsystems

Vapour–liquid equilibrium data are reported for the ternary tert-butyl methyl ether+tert-butanol+2,2,4-trimethylpentane and the three binary tert-butyl methyl ether+tert-butanol, tert-butyl methyl ether+2,2,4-trimethylpentane, tert-butanol+2,2,4-trimethylpentane subsystems. The data were measured isothermally at 318.13, 328.20, and 339.28 K covering pressure range 15–100 kPa. Azeotropic data are presented for the tert-butanol+2,2,4-trimethylpentane system. Molar excess volumes at 298.15 K are given for the three binary systems. The binary vapour–liquid equilibrium data were correlated using Wilson, NRTL, and Redlich–Kister equations; the parameters obtained were used for calculation of phase behaviour in ternary system and for subsequent comparison with experimental data.     

Phase equilibria for binary systems of octane boosters with 2,2,4-trimethylpentane

Isobaric vapor–liquid equilibrium data at 95.96 kPa for the three binary systems of 2,2,4-trimethylpentane with methyl tert-butyl ether, di-isopropyl ether and dimethoxymethane are determined. A Swietoslawski type ebulliometer is used for the measurements. The experimental T–x data are used to estimate Wilson parameters and the parameters, in turn, are used to calculate vapor phase compositions and activity coefficients. All the systems studied here do not exhibit azeotropes and behave like non-ideal solutions.     

Synthesis, characterization and antifungal activity of copper (II) complexes of sterically hindered o-diphenol derivatives

Cu (II) complexes with 3,5-di(tert-butyl)-1,2-benzenediol (I), 4,6-di(tert-butyl)-1,2,3-benzentriol (II) and sulfur-containing sterically hindered o-diphenol derivatives such as 4,6-di(tert-butyl)-3-(2-hydroxyethylsulfanyl)-1,2-benzenediol (III) and 2-[4,6-di(tert-butyl)-2,3-dihydroxyphenylsulfanyl]acetic acid (IV) have been synthesized and characterized by means of elemental analysis, TG/DTA, FT-IR, ESR, XPS, XPD and conductivity measurements. Antifungal activities of these ligands and their respective Cu (II) complexes have been determined against Aspergillus niger, Fusarium sp., Penicillium lividum, Mucor sp. and Botrytis cinerea. Most of the compounds (both the free ligands and the complexes) exert pronounced antifungal activities (RI  70%), and virtually all of them (apart from the Cu(L^II)₂ complex) have the highest inhibitory properties (RI = 100%) against B. cinerea.     

The relationship between thermodynamic stabilities of carbenium ions in the gas phase and in aqueous solution: A wide scope study

The thermodynamics of the reaction involving R_ref = tert-butyl and 21 carbenium ion/alcohol systems has been studied at the MP2/6-311+G(3d, 2p)//MP2/6-311+G(d, p) level. The results have been compared to the experimental data for the same systems in solution. The range of structural effects spans 102 kcal mol⁻¹ in the gas phase and is the widest ever examined. A physically meaningful correlation has been found. Phenyl-substituted systems are among the most important exceptions.     

Carbonylation of tert-butyl alcohol over H-zeolites

The Koch-type carbonylation of tert-butyl alcohol was studied over H-type zeolites. It was found that the catalytic carbonylation of a large amount of tert-butyl alcohol relative to the acidic sites of the H-zeolites in organic solvents requires an elevated temperature and CO pressure, although previous solid state NMR studies have revealed that the transformation of tert-butyl alcohol of an amount comparable to the acidic sites into 2,2-dimethylpropanoic acid proceeds just upon the CO co-adsorption in the H-zeolites at room temperature and atmospheric pressure. The catalytic performance of different H-zeolites and the influence of CO pressure, H₂O addition and solvent effects on the carbonylation of tert-butyl alcohol have been investigated. H-ZSM-5 gives the highest selectivity for 2,2-dimethylpropanoic acid due to its adequate pore dimensions. The present work indicates the possible industrial application of solid acids as carbonylation catalysts instead of liquid acids for the Koch reaction to produce tert-carboxylic acids.     

Excess molar enthalpies of the ternary mixtures: methyl tert-butyl ether + 3-methylpentane + (n-decane or n-dodecane) at 298.15 K

Excess molar enthalpies, measured at 298.15 K in a flow microcalorimeter, are reported for the two ternary mixtures formed by mixing either methyl tert-butyl ether with binary mixtures of 3-methylpentane and either n-decane or n-dodecane. Smooth representations of the ternary results are presented and used to construct constant excess molar enthalpy contours on Roozeboom diagrams. It is found that the Liebermann and Fried model also provided good representation of the ternary results, using only the physical properties of the components and their binary mixtures.     

Method for determination of methyl tert-butyl ether in gasoline by gas chromatography

A simple method for the determination of methyl tert-butyl ether (MTBE) in gasoline has been developed. The separation of MTBE from other analytes was controlled by the use of gas chromatography–mass spectrometry in the full scan mode using the characteristic primary, secondary and tertiary ions m/z 73, 57 and 43. The sample mass spectrum did not show any superimposition of other analytes. The separation from the common gasoline component 2-methylpentane was sufficient for reliable quantitation. An application of the developed conditions using gas chromatography with flame ionization detection was performed by the analysis of regular, euro super, super premium unleaded and ‘Optimax’ gasoline from petrol stations in the area of Frankfurt/Main, Germany. Regular unleaded gasoline shows an average MTBE content of 0.4% (w/w), whereas the MTBE content in euro super gasoline varies between 0.4 and 4.2% (w/w). The blending of MTBE to super premium has increased from 8.2% (w/w) in 1998 to 9.8% (w/w) on average in 1999. The recently introduced gasoline ‘Optimax’ shows an average MTBE content of 11.9% (w/w). The presented method might also be used for the analysis of other ethers, such as ethyl tert-butyl ether, which requires the use of another internal standard.     

Alkylation of p-cresol with tert-butanol catalyzed by heteropoly acid supported on zirconia catalyst

Butylation of p-cresol by tert-butanol was catalyzed by 12-tungstophosphoric acid supported on zirconia (TPA/ZrO₂) under flow conditions. Catalysts prepared with different TPA loading (5–30 wt.%) were calcined at 1023 K and acidity was estimated by temperature programmed desorption (TPD) of NH₃. Fifteen percent TPA/ZrO₂ showed the highest acidity and found to be the most active catalyst in butylation of p-cresol. The effects of temperature, space velocity (LHSV) and molar ratio of the reactants on the conversion of p-cresol and products selectivities were optimized and the optimum reaction conditions evaluated were 403 K, tert-butanol/p-cresol (Bu/Cr) molar ratio 3 and LHSV 4 h⁻¹. Under the optimized conditions, conversion of p-cresol was found to be 61 mol% with product selectivity for 2-tert-butyl-p-cresol (TBC) 81.4%, 2,6-di-tert-butyl-p-cresol (DTBC) 18.1% and tert-butyl-p-tolyl ether (ether) 0.5%. Study of time on stream (TOS) performed as a function of time for 100 h showed that the loss in activity in terms of conversion of p-cresol was 6%.     

Two-photon chemistry in the laser jet: generation of radical intermidiates and their photochemical transformations

The novel laser jet technique provides sufficiently high photon densities to permit the observation of the photochemistry of photochemically generated radicals (two-photon chemistry) in the liquid phase. Four recent applications of this novel photochemically useful method are presented: these include the photochemistry of hydroxydiphenylmethyl, 9-hydroxyxanthenyl, diphenylmethyl, and benzoyl radicals under laser jet and normal photolysis conditions.

The regioselectivity of cross-coupling reactions of hydroxydiphenylmethyl or 9-hydroxyxanthenyl radicals with solvent-derived radicals changes when these species are electronically excited,i.e. under the high intensity conditions of the laser jet, cross-coupling at the para position (head-to-tail combination) is significantly enhanced relative to the normal coupling mode at the hydroxy-bearing radical site (head-to-head combination). Semiempirical calculations of the spin density distributions for the ground and first excited states of the radicals confirm the change in spin density from the hydroxy-bearing carbon atom to the conjugating benzene rings in these radical species on photoexcitation.

For the diphenylmethyl radical, two reaction pathways have been observed under the high photon densities of the laser jet: the electronically excited diphenylmethyl radical can either abstract a chlorine atom from carbon tetrachloride through an electron transfer process or can be photoionized on further photoexcitation (multiphoton chemistry). The resulting benzhydryl cation was trapped by methanol as the corresponding ether product, which unequivocally demonstrates that carbene formation by photoejection of a hydrogen atom does not take place under laser jet photolysis conditions.

An advantage of the high photon densities produced in laser jet photolysis is the high steady state concentration of short-lived transients that are generated, which enable unprecedented intermolecular reactions to be observed. Thus, about a millimolar concentration of tert-butoxy radicals can be obtained in the laser jet photocleavage of tert-butyl peroxide. When the tert-butoxy radicals are produced in the presence of benzaldehyde, the main product is tert-butyl benzoate. If carbon tetrachloride is also present, chlorobenzene can be detected. This is rationalized as the product derived from chlorine abstraction by phenyl radicals, which are presumably produced by the photodecarbonylation of benzoyl radicals.

An alternative method of obtaining benzoyl radicals is the two-photon cleavage of benzil. The laser jet photolysis of benzil in tert-butyl peroxide yields mainly tert-butyl benzoate, whereas in carbon tetrachloride, benzoyl chloride, chlorobenzene and ,,-trichloroacetophenone are observed. The first two products result from chlorine atom abstraction by the photochemically generated benzoyl and phenyl radicals, and the last product from in-cage cross-coupling between benzoyl and trichloromethyl radicals.

Such product studies provide detailed mechanistic information on the photochemical behaviour of electronically excited, short-lived transients which complements nicely the kinetic and spectral data of time-resolved laser flash studies. Consequently, the laser jet technique constitutes a valuable tool for determining the mechanism of two- photon reactions.     

Unsymmetric-1,3-disubstituted imidazolium salt for palladium-catalyzed Suzuki–Miyaura cross-coupling reactions of aryl bromides

A series of 1-(ferrocenylethyl)-3-substituted-imidazolium salts [3-substitute = 2,6-di(iso-propyl)phenyl (1a), 2,4,6-trimethylphenyl (1b), tert-butyl (1c), 1-Ad (1d), cyclohexyl (1e)] have been synthesized from a racemic ferrocenylethyl acetate and the corresponding N-substituted imidazole in high yields (70–94%). A combination of Pd(OAc)₂ and 1a–d was found to form an excellent catalyst system for the Suzuki–Miyaura cross-coupling reactions of aryl bromides with phenylboronic acid in the presence of Cs₂CO₃.     

Percarbamate de t-butyle et ses dérivés N-alkylés, N,N-dialkylés et N-azacyclaniques: préparation et thermolyse en solution

Several tert-butyl percarbamates have been prepared by the reaction of amines with tert-butyl imidazolylpercarboxylate. The thermal decomposition of these peresters in solution led to the characteristic products of homolytic processes. The kinetic study of the thermolysis has been performed by Differential Scanning Microcalorimetry. It showed the influence of the nitrogen atom substitution on the percarbamate stability. The kinetic study of the decompositions of percarbamates derived from cyclic amines showed an important effect of the cycle size on the rate constant. Very different transition state levels are responsible for this phenomenon. A stereoelectronic origin—from the overlapping of the p-orbital of the nitrogen atom and the π bond of the carboxyl—has been advanced to account for this result.     

Vapor–liquid equilibria and excess properties for methyl tert-butyl ether (MTBE) containing binary systems

Methyl tert-butyl ether (MTBE) is recently widely used in the chemical and petrochemical industry as a non-polluting octane booster for gasoline and as an organic solvent. The isobaric or isothermal vapor–liquid equilibria (VLE) were determined directly for MTBE+C₁–C₄ alcohols. The excess enthalpy (H^E) for butane+MTBE or isobutene+MTBE and excess volume (V^E) for MTBE+C₃–C₄ alcohols were also determined. Besides, the infinite dilute activity coefficient, partial molar excess enthalpies and volumes at infinite dilution (γ^∞, H^E,∞, V^E,∞) were calculated from measured data. Each experimental data were correlated with various g^E models or empirical polynomial.     

Chalcogen Effect of Atom Substitution on the Properties of Tris(2,4,6-trichlorophenyl)methyl(TTM) Radical

Luminescent open-shell organic radicals have recently been regarded as one of the most potential materials in organic light-emitting diodes(OLEDs). Herein, we have synthesized two new organic radicals, namely tris{4-[4-(tert-butyl)phenoxy]-2,6- dichlorophenyl}methane radical(TTM-O) and tris(4-{[4-(tert-butyl)- phenyl]thio}-2,6-dichlorophenyl)methane radical(TTM-S), by the substitution of chalcogen atom elements at the para position of conventional tris(2,4,6-trichlorophenyl)methyl(TTM) radical moiety. Interestingly, both TTM-O and TTM-S exhibited significantly enhanced photostability compared with the unsubstituted TTM radical parent. Moreover, the chalcogen atom also had a crucial impact on the photoluminescence quantum yield(PLQY) of the radicals, i.e., the PLQY of TTM-S was greatly enhanced compared to TTM radical while TTM-O was nearly non-emissive. Particularly, TTM-S showed intense PLQY of 37.54% and 185-fold longer photostability than that in cyclohexane solution of TTM.     

Activity coefficient at infinite dilution, azeotropic data, excess enthalpies and solid–liquid-equilibria for binary systems of alkanes and aromatics with esters

Binary azeotropic data have been measured at different pressures for ethyl acetate + heptane, methyl acetate + heptane, isopropyl acetate + hexane and isopropyl acetate + heptane by means of a wire band column. Additionally activity coefficients at infinite dilution have been determined for ethyl acetate and isopropyl acetate in decane and dodecane in the temperature range between 303.15 and 333.15 K with the help of the dilutor technique. Furthermore excess enthalpies for the binary systems methyl acetate + hexane, methyl acetate + decane, ethyl acetate + hexane and ethyl acetate + decane at 363.15 and 413.15 K have been studied with the help of isothermal flow calorimetry. Finally solid–liquid equilibria for the systems ethyl myristate + benzene and ethyl myristate + p-xylene have been investigated by a visual technique. All these data have been used for the revision and extension of the group interaction parameters of the group contribution method modified UNIFAC (Dortmund) and the group contribution equation of state VTPR. The experimental data was compared with the results predicted using the group contribution method modified UNIFAC (Dortmund) and the group contribution equation of state VTPR.     

Boiling points for five binary systems of sulfolane with aromatic hydrocarbons at 101.33 kPa

Boiling points have been determined at 101.33 kPa for the binary mixtures of sulfolane+o-xylene, sulfolane+m-xylene, sulfolane+p-xylene, sulfolane+ethylbenzene and sulfolane+1,2,4-trimethylbenzene. Calculations of the non-ideality of the vapor phase were made with the second virial coefficients evaluated from the Hayden–O’Connell method. The binary parameters for five activity coefficient models (Margules, van Laar, Wilson, NRTL and UNIQUAC) have been fitted with the experimental boiling points measured in this work. A comparison of model performances has been carried out using the criterion of the average absolute deviations in boiling point. The activity coefficient of the component in the liquid phase is discussed based on the UNIFAC model with the consideration of the dipole–dipole interactions.     

SBA-15 supported HPW: Effective catalytic performance in the alkylation of phenol

SBA-15 was synthesized using non-ionic surfactant as the structure directing agent at 40 °C. It was then impregnated with different loadings (10, 30, 50 and 70%) of phosphotungstic acid. They were characterized by XRD, N₂ adsorption, FT-IR and DRIFT techniques. The physicochemical characterization revealed that SBA-15 could accommodate discrete phosphotungstic acid due to its large pore volume and high surface area. The catalytic activity of these materials was examined in the vapour phase tert-butylation of phenol using tert-butyl alcohol as the alkylating agent. The influence of reaction parameters such as reaction temperature, reactant feed ratio, WHSV and time on stream was studied, and the results were correlated with physicochemical characteristics of the catalysts. 4-tert-Butyl phenol was observed as the major product with high selectivity. Among the catalysts, 30% phosphotungstic acid supported SBA-15 showed high phenol conversion under optimum conditions, which is significantly higher than either phosphotungstic acid loaded mesoporous AlPO or AlMCM-41.     

Vapor–liquid equilibria and excess volumes of the binary systems ethanol + ethyl lactate, isopropanol + isopropyl lactate and n-butanol + n-butyl lactate at 101.325 kPa

Isobaric vapor–liquid equilibrium data have been experimentally determined at 101.3 kPa for the binary systems ethanol + ethyl lactate, isopropanol + isopropyl lactate and n-butanol + n-butyl lactate. No azeotrope was found in any of the systems. All the experimental data reported were thermodynamically consistent according to the point-to-point method of Fredenslund. The activity coefficients were correlated with the NRTL and UNIQUAC liquid-phase equations and the corresponding binary interaction parameters are reported. The densities and derived excess volumes for the three mixtures are also reported at 298.15 K.     

钯催化炔丙醇与叔丁基异腈选择性合成吡咯并呋喃衍生物和氨基甲酸酯

报道了钯催化下炔丙醇与叔丁基异腈反应高选择性合成吡咯并呋喃衍生物和氨基甲酸酯的新方法.在10%(摩尔分数)Pd(OAc)₂与110%(摩尔分数)LiBr存在下,一分子炔丙醇与三分子叔丁基异腈在水的参与下发生“有序的”异腈三重插入反应,以56%～73%的产率高选择性地生成了吡咯并呋喃衍生物;而在10%(摩尔分数)Pd(PPh₃)₄和110%(摩尔分数)K₃PO₄存在下,一分子炔丙醇与一分子叔丁基异腈在空气中氧气的参与下发生简单氧化偶联反应,以51%～74%的产率生成了氨基甲酸酯.该方法仅通过简单改变钯催化剂与盐的种类就能得到不同产物,且反应选择性高,分别为吡咯并呋喃亚胺衍生物和氨基甲酸酯提供了有吸引力的合成途径.     

Alcohols controlled selective radical cyclization of 1,6-dienes under mild conditions

An efficient procedure for the selective preparation of hydroxy-, carbonyl- and acetal-containing 2-pyrrolidinones has been developed through radical cyclization of 1,6-dienes initiated by α-C(sp³)-H functionalization of alcohols. This protocol could be conducted at catalyst-free conditions at relatively low temperature (80 ℃) by employing commercially available tert-butyl peroxybenzoate (TBPB) as the oxidant.     

含叔丁基/异丁基二胺的可溶性透明聚酰亚胺的合成与性能

通过分子设计合成了异丁基桥联2-叔丁基苯胺的新型二胺单体4,4′-(2-异丁基)双(2-叔丁基苯胺), 并将其分别与4种商品化芳香族二酐经高温“一步法”缩聚制得了系列聚酰亚胺(PI)树脂. 采用多种测试手段研究PI的结构和性能, 结果表明, 该系列新型聚酰亚胺不但可溶于N-甲基吡咯烷酮及N,N-二甲基甲酰胺等高沸点溶剂, 而且在乙酸乙酯和三氯甲烷等低沸点溶剂中也具有良好的溶解性. 该系列PI保持了良好的热稳定性, 在N₂中5%热失重温度均在480 ℃以上, 玻璃化转变温度(T_g)介于307~356 ℃之间. 经溶液刮涂制得的PI薄膜具有良好的光学透明性, 在可见光区平均透过率可达82.3%~89.1%, 截止波长介于313~363 nm之间. 同时, 该系列PI薄膜还具有良好的机械性能和疏水性, 有望应用于光伏发电及柔性显示等领域.