Liquid-liquid equilibrium in the toluene-methyl ethyl ketone-water system

For the toluene-methyl ethyl ketone-water system the liquid-liquid equilibrium tie-line data have been determined at 40 and 0°C and the binodal curve for this system has been determined at 40, 0 and −10°C. The tie-line data at 40 and 0°C could be correlated with good accuracy using NRTL and UNIQUAC model equations.     

A thermoanalytical study of the cure of xylok 225 resin

The cure of Xylok 225 resin with a range of concentrations of hexamethylene tetramine has been studied by DTA, DTA-TG and DSC. The process has also been followed by IR spectroscopy. Two reaction peaks were observed during the cure, an exotherm occurring near to 150°C and an endotherm near to 250°C. The exotherm appeared to be affected by the concentration of hexamethylene tetramine, at a low concentration (4.8%) its onset was delayed until near 190°C, whilst at a higher concentration (13.0%) the heat of reaction was diminished. Both the exothermic and endothermic phases of cure were accompanied by evolution of volatiles.     

Equilibrium of the reaction between dissolved sodium sulfide and biologically produced sulfur

The equilibrium of the heterogeneous reaction between dissolved sodium sulfide and biologically produced sulfur particles has been studied. Biologically produced sulfur was obtained from a bioreactor of a hydrogen sulfide removal process in which the dominating organism is Thiobacillus sp. W5. Detailed knowledge of this reaction is essential to understand its effect on the process. The results were compared with the equilibrium of the reaction of sulfide with ‘inorganic’ elemental sulfur. The equilibrium between dissolved sodium sulfide and biologically produced sulfur particles can be described by an equilibrium constant, K_x, which consists of a weighted sum of constants for polysulfide ions of different chain length, rather than a true single equilibrium constant. For biologically produced sulfur pK_x = 9.10 ± 0.08 (21 °C) and 9.17 ± 0.09 (35 °C) with an average polysulfide chain length x = 4.91 ± 0.32 (21 °C) and 4.59 ± 0.31 (35 °C). The pK_x value for biologically produced sulfur is significantly higher than for reaction of dissolved sodium sulfide with inorganic sulfur (pK_x = 8.82; 21 °C). This difference is probably caused by the negatively charged polymeric organic layer, which is present on biologically produced sulfur but absent with “inorganic” sulfur. Specific binding of polysulfide ions to the organic layer results in a higher polysulfide concentration at the reaction site compared to the bulk concentration. This results in an apparent decrease of the measured equilibrium constant, K_x.     

Kinetics and hazards of thermal decomposition of methyl ethyl ketone peroxide by DSC

Differential scanning calorimetry (DSC) was applied to analyze thermal decomposition of methyl ethyl ketone peroxide (MEKPO). Thermokinetic parameters and thermal stability were evaluated. MEKPO decomposes in at least three exothermic decomposition reactions and begins to decompose at 30–32 °C. The total heat of decomposition is 1.26 ± 0.03 kJ g⁻¹. Thermal decomposition of MEKPO can be described by a model of two independent reactions: the first is decomposition of a less stable isomer of MEKPO, followed by decomposition of the main isomer, after which an exothermic reaction of the reaction products with the solvent, dimethyl phthalate. The results can be applied for emergency relief system design and for emergency rescue strategies during an upset or accident.     

Kinetic study of thermal decomposition of CoOOH

The kinetics of the thermal decomposition of CoOOH powder has been studied isothermally in a temperature range of 260—310°C in air. The reaction was found to proceed by the advance of a two-dimensional reaction interface. The kinetics results indicate that there are two phases in the decomposition in this temperature range: up to 280°C with an activation energy E₁ = 34.75 kcal mol⁻¹ and above 280°C with E₂ = 18.91 kcal mol⁻¹. A reaction mechanism is proposed to account for these observations.     

Solution properties of polyurethane

Polyurethane was fractionated and the fractions were characterized by gel permeation chromatography (GPC) and viscometry. The intrinsic viscosities of polyurethane in ten solvents varying in their polarity were determined and are in the order of mineral spirit < acetone < cyclohexane < cyclohexanone < xylene < ethyl benzene < toluene < benzene < methyl ethyl ketone < tetrahydrofuran. The Mark-Houwink relations suggested that solvent blend MEK: n-heptane (1:3) is a poor solvent with an a value of 0·52 and tetrahydrofuran is a good solvent with an a value of 0·78. The weight average molecular weight has been estimated by an extrapolation technique based on a linear relationship between the viscosity average molecular weight _v and the Mark-Houwink constant. The weight average molecular weights obtained from viscosity studies were used to evaluate the unpertureb dimension of the chain.     

The synthesis and thermotropic behaviour of an ethyl cellulose derivative containing azobenzene-based mesogenic moieties

An ethyl cellulose derivative containing azobenzene-based mesogenic moieties was prepared by the reaction of 4-methoxyazobenzene-4'-oxyacetic acid and ethyl cellulose by esterification in the presence of N,N' -dicylcohexylcarbodiimide and 4-dimethylaminopyridine. Its chemical structure and liquid crystalline properties were characterized by FTIR, 1 H NMR, POM, DSC and WAXD. The degree of substitution of the cellulose backbone by the azobenzene-based mesogenic moieties is 0.9. The polymer is thermotropic and exhibits liquid crystalline behaviour over the temperature range 125-172°C.     

High temperature reaction of SiCl4 and O2 in quartz tubes

The reaction between SiCl₄ and O₂ at 1 atm between 25 and 1200°C has been followed by mass spectrometry. Below 600°C no reaction with O₂ is noted. Above 600°C the reaction proceeds in two steps. Between 800 and 1000°C the ²⁸Si/³²O₂ peak height ratio is constant with no evolution of Cl₂. It is suggested that silicon oxychlorides are being formed in this temperature regime. Above 1000°C the reaction between SiCl₄ and O₂ intensifies with concomitant production of Cl₂. It is suggested that above 1000°C the reaction SiCl₄ + O₂ → SiO₂ + Cl₂ becomes important.

At low temperatures (<800°C) adsorbed H₂O and OH groups from the surface of the fused silica tube react with SiCl₄ to form HCl. The importance of this reaction decreases with increasing temperature. The increased production of HCl above 1000°C is ascribed to H₂O and H₂ diffusing from the tube.     

Bis[bis{(diphenylphosphinyl)methyl}ethyl phosphinate](ethanol) copper(II) perchlorate: synthesis, crystal and molecular structure

Bis[bis{(diphenylphosphinyl)methyl}ethyl phoshinate]bis(ethanol) metal(II) perchlorate complexes, where METAL = Co, Ni or Cu, have been prepared by the reaction of metal perchlorates and bis[(diphenylphosphinyl)methyl]ethyl phosphinate, (RPOEt), in absolute ethanol. The crystal structure of the copper complex is triclinic, space group P , a = 13.688(7) Å, b = 14.424(10) Å, c = 9.865(2) Å, = 110.43(4)°, β = 90.13(2)°, γ = 115.54(4)°, V = 1619.8 ų, Z = 1 and refined to R = 0.048 (R_w = 0.057). The structure consists of complex cations surrounded by perchlorate anions. Two RPOEt ligands and two ethanols are coordinated to the copper atom situated at the centre of symmetry 0, 0, 0. The RPOEt ligand is bidentate [Cu---O distances 1.969(4) Å, 2.312(4) Å], but the third oxygen atom from phosphoryl bonds is hydrogen bonded [2.669(6) Å], to the oxygen atom of ethanol molecule coordinated to the copper at 1.988(4) Å. The conformations of the ligand and chelate rings, magnetic data, molar conductance values, infrared and electronic spectra are given.     

Novelties of cyanide displacement reaction in ibuprofen amide process by phase transfer catalysis: Solid–liquid versus solid–liquid (omega)–liquid systems

This work deals with the phase transfer catalysed cyanide displacement reaction on 1-(4-isobutyl phenyl) ethyl chloride to synthesize 2-(4-isobutyl phenyl) propionitrile, which is an intermediate for the synthesis of ibuprofen analogs, belonging to a class of NSAID (nonsteroidal anti-inflammatory drugs). The reaction was studied using solid–liquid phase transfer catalysis (S-L PTC) with trace quantities of water, forming the so-called omega phase at 90 °C. The rates of reaction and selectivity to the product are enhanced in the S-L(org.)-L (ω) PTC in comparison with S-L PTC, which in turn is superior to L-L PTC; the latter suffers from the disadvantage of side reactions in the aqueous phase. In the current work, the effects of various parameters such as catalyst structure, catalyst loading, substrate loading and temperature were studied on the conversion and rates of reaction of 1-(4-isobutyl phenyl) ethyl chloride with solid sodium cyanide under S-L and S-L(ω)-L PTC at 90 °C with toluene as the organic solvent. Tetrabutylammonium bromide (TBAB) was found to be the best catalyst. The role of omega liquid phase in intensification of the S-L PTC was theoretically and experimentally investigated. The kinetic constants have been determined and the apparent activation energy is found as 4.2 kcal/mol, which suggests that the reaction is quite fast, which is likely to bring in mass transfer effects.     

Microwave-assisted solvent free synthesis of hydroxy derivatives of 4-methyl coumarin using nano-crystalline sulfated-zirconia catalyst

Nano-crystalline sulfated-zirconia solid acid catalyst has been studied for microwave-assisted solvent free synthesis of hydroxy derivatives of 4-methyl coumarin by Pechmann reaction. The catalyst showed good activity for activated m-hydroxy phenol substrates, viz., phloroglucinol and pyrrogallol with ethyl acetoacetate for the synthesis of 5,7-dihydroxy 4-methyl coumarin and 7,8-dihydroxy 4-methyl coumarin, respectively, showing significant yields ranging from 78 to 85% within 5–20 min at 130 °C. However, the less activated phenol and m-methyl phenol was observed to be inactive for the synthesis of 4-methyl coumarin and 4,7-dimethyl coumarin, respectively, under the studied experimental conditions.     

Mesoporous material as catalyst for the production of fine chemical: Synthesis of dimethyl phthalate assisted by hydrophobic nature MCM-41

Aluminum, iron and zinc containing MCM-41 molecular sieves were prepared by the hydrothermal method. The catalyst was characterized by the XRD, BET (surface area), FT–IR and ²⁹Si, ²⁷Al MAS–NMR techniques. The catalytic activity of these molecular sieves was tested with esterification reaction used with phthalic anhydride (PAH) and methanol (MeOH) in the autoclave at 135 °C, 150 °C and 175 °C. Conversion increases with an increase in temperature and mole ratio. The activity of these catalysts followed the order: Al-MCM-41 (112) > Fe-MCM-41 (115) > Al-MCM-41 (70) > Al-MCM-41 (52) > Fe-MCM-41 (61) > Al, Zn-MCM-41 (104) > Al-MCM-41 (30). The reaction yielded both monomethyl phthalate (MMP) and dimethyl phthalate (DMP). The nature of the catalyst sites has been proposed using with water as an impurity. The selectivity of the dimethyl phthalate increases with increase in temperature and mole ratio. The weight of the catalyst was optimized at 0.07 g. The hydrophilic and hydrophobic nature of the catalyst has been explained by the influence of water and the external surface acidity also facilitates the reaction and this has been confirmed by the supporting reaction.     

Catalytic effect of zinc oxide on the reduction of barium sulfate by methane

Reduction of barium sulfate by methane was investigated in this work. The thermogravimetric method was used to obtain kinetic parameters of the reaction in the temperature range of 900–975 °C at atmospheric pressure. The kinetics of the reaction has been studied both in the absence and presence of zinc oxide as a catalyst. The conversion–time data have been interpreted by using the grain model, and the effect of catalyst on the kinetic parameters has been elucidated. It was found that zinc oxide acted as fairly strong catalyst for the reaction, especially at higher temperatures. At about 975 °C the reaction rate constant was increased more than 7 times by using 2% of zinc oxide. This enhancement in the rate constant is valuable for industries.     

Microwave spectrum and rotational isomers of ethyl fluoroformate

The microwave spectrum of ethyl fluoroformate displays strong a-type R branch transitions from two rotameric forms. One species (extended form) has rotational constants A₀ = 9191.3(9) MHz, B₀ = 2112.61(1) MHz, C₀ = 1756.73(1) MHz which are consistent with a syn-anti (τ₁(OCOC) = 0°, r₂(cocc) = 180°) planar heavy atom structure. The second species (compact form) has rotational constants A₀ = 7760(3) MHz, B₀ = 2388.38(4) MHz, C₀ = 2102.47(3) MHz which are consistent with a syn-gauche (τ₁(ococ) = 0°, τ₂(cocc) ˜ 90°) structure. The two conformational forms have approximately equal energy (0 ± 40 cm⁻¹). Four vibrational satellites of the extended species have been analyzed yielding a torsional frequency around the O-ethyl bond of 70(10) cm⁻¹. Three vibrational satellites attributed to the O-ethyl torsion of the compact species have been analyzed yielding a vibrational frequency of 90(10) cm⁻¹. Approximate Fourier coefficients of a three term potential function for internal rotation about the O-ethyl bond have been determined. Vibrational satellites attributed to the first excited states of the O-ester torsion have been analyzed for both conformers. The torsional vibrational frequency around the O-ester bond is 110(15) cm⁻¹ for the extended conformers and 120(20) cm⁻¹ for the compact.     

A kinetic study of C- and O-alkylation of some cyclic β-keto esters

The reactions of sodio-2-carbethoxycyclanones of 5, 6 and 8 ring members (I-5, I-6, I-8) with isopropyl iodide in dimethylsulfoxide (DMSO) have been studied kinetically at three temps. Three competing second order reactions occur: isopropylation at carbon, isopropylation at oxygen and propene formation. The total rate constants were dissected into individual rate constants by an independent measurement of propene formation and by GLC of the alkylation product mixtures. At 30°, the C/O ratios for I-5, I-6 and I-8 are 1·74, 1·34 and 7·72 respectively. Increasing temps favor O-alkylation in all cases since it has the higher enthalpy of activation of the two alkylation processes. Relative rates of C-alkylation at 30° for I-5:I-6:I-8 are 1·7:1:4·4 whereas for O-alkylation the relative rates are 1·3:1:0·8. The insensitivity of the O-alkylation process to structural change in the anion and the anomalous position of I-8 in the reaction series for O-alkylation are attributed to a coincidence of the experimental temperature and the isokinetic temp.     

Synthesis and mesomorphic properties of some derivatives of 2-methylcyclohex-2-ene-4-one-1-carboxylic and cis-2,6-dimethyl cyclohex-2-ene-4-one-1 -carboxylic acids

Mesomorphic derivatives prepared from ethyl esters of 2-methylcyclohex-2-ene-4-one-1-carboxylic and cis-2,6-dimethylcyclohex-2-ene-4-one-1-carboxylic acids have been synthesized. It has been shown that the compounds obtained are characterized by a lower nematic—isotropic transition temperature (10-20°C) and a considerably narrower nematic range in comparison with the analogous derivatives of 4-alkylcyclohex-3-ene-carboxylic and trans-4-alkylcyclohexane-carboxylic acid.     

A short large scale synthesis of (±) sarkomycin esters

(±) Sarkomycin ethyl ester has been prepared in four steps from ethyl acrylate.     

The conformations of 1,2-acenaphthene derivatives and steric interaction of contiguous nitroxy groups

Inter-oxygen distances and conformational flexibility were estimated for cis- and trans-1,2-acenaphthenediol from X-ray data, intramolecular hydrogen bonding, the kinetics of glycol cleavage, and cyclization experiments. The optical and NMR spectra of the isomeric dinitrate esters and related compounds in solution showed significant differences. The symmetric and anti-symmetric stretching bands of the nitroxy group occurred at 1276 ± 2 cm⁻¹ and 1639 ± 7 cm⁻¹ respectively in the trans-dinitrate and in ethyl and benzyl nitrates and were shifted to higher frequencies by 9 cm⁻¹ and 16 cm⁻¹ respectively in the cis-dinitrate. The analogy to similar effects observed in cyclic 1,2-diketones, -haloketones, and o-halonitrobenzenes suggested intramolecular interaction of the contiguous nitroxy groups.

The reaction of the dinitrates with pyridine at 25° was pseudo first-order and the ratio k_trans/k_cis of 6·5 was consistent with an E_CO mechanism involving nitroxy group interaction in the cis isomer.     

The formation and physicochemical properties of magnesium manganates

The effects of calcination temperature, molar ratio and the doping by CeO₂ on the solid–solid interactions, surface and catalytic properties of Mn/Mg mixed oxide system have been studied by XRD, nitrogen adsorption at −196 °C and the catalytic decomposition of hydrogen peroxide at 20, 30, and 40 °C.

The results revealed that the manganese oxides interacted with magnesium oxide to yield well crystallized magnesium manganates at temperatures starting from 600 °C, this reaction found to be affected by the molar ratio of the reacted oxides present and also by the dopant content. However, the treatment of the Mn/Mg mixed oxide system with increasing amounts of manganese and cerium oxides followed by calcination at 400–800 °C brought about an increase in the catalytic activity of the resulting solids, whilst the opposite effect was observed in the surface area of the investigated solids. These treatments resulted in an increase in the particle size of MgO and a decrease in both the activation energy of sintering of the investigated system and that necessary for hydrogen peroxide decomposition reaction.     

Synthesis of dimethyl carbonate by vapor phase oxidative carbonylation of methanol over Cu-based catalysts

Dimethyl carbonate (DMC) synthesis reaction by oxidative carbonylation of methanol has been studied using vapor phase flow reaction system in the presence of Cu-based catalysts. A series of Cu-based catalysts were prepared by the conventional impregnation method using activated carbon (AC) as support. The effect of various promoters and reaction conditions on the catalytic reactivities were intensively evaluated in terms of methanol conversion and DMC selectivity. The morphological analysis by X-ray diffraction and SEM was also conducted in order to characterize the emloyed catalysts. Regardless of catalyst compositions, the optimal reaction temperature for oxidative carbonylation of methanol was found to be around 120–130°C. The reaction rate was too slow below 100°C, while too much by-products was produced above 150°C. Among the various catalysts employed, CuCl₂/NaOH/AC catalyst with the molar ratio of OH/Cu=0.5–1.0, has shown the best catalytic performance, which appears to have a strong relationship with the formation of intermediate species, Cu₂(OH)₃Cl.