Longer Alkyl Chain Length Research Articles

Silica grafted imidazolium-based ionic liquids: efficient heterogeneous catalysts for chemical fixation of CO2 to a cyclic carbonate

Imidazolium-based ionic liquids with varied alkyl chain lengths bearing different anions (Cl−, Br− and I−) were synthesized and immobilized onto the commercial silica surface (IMIS). These heterogeneous catalysts exhibited high catalytic activities and selectivities in the cycloaddition of carbon dioxide to allyl glycidyl ether (AGE). The immobilized ionic liquids with longer alkyl chain length and more nucleophilic anion showed higher activity. In particular, compared with pristine IMIS, zinc halide-combined IMIS (IMIS-Zn) with Cl− exhibited an increased activity, while the IMIS-Zn with Br− and I− showed lower activity than IMIS itself. In addition, the textures of silica supports (surface area and average pore size) have a great impact on the catalytic activity owing to the substance-confined diffusion effects. The recycling experiments showed that the resulting heterogeneous catalysts exhibited good reusability.

Application of MELC and MEEKC for the Analysis of Paracetamol and Related Impurities in Suppositories

Rapid MELC and MEEKC methods were developed for paracetamol suppository assay. MELC methods for paracetamol analysis and for separation of paracetamol and its impurities were previously reported. In this study, further development of MEEKC methods and a MELC method using anionic and cationic microemulsions gave excellent validation results for paracetamol content in suppositories. SDS Microemulsion instability resulted in poor reproducibility for impurity separations using gradient elution. A novel isocratic CTAB MELC method achieved reproducible separation of paracetamol and its impurities at 0.1% levels. MEEKC methods using SDS and CTAB microemulsions resolved all of the impurities however detection at 0.1% levels was not possible. These methods gave significant benefits in terms of reduced sample pre-treatment requirements. CTAB microemulsions had greater solubilising power than their SDS equivalent and were more stable due to their longer alkyl chain length.

Catalytic performance of quaternary ammonium salts in the reaction of butyl glycidyl ether and carbon dioxide

The synthesis of cyclic carbonate from butyl glycidyl ether (BGE) and carbon dioxide was performed in the presence of quaternary ammonium salt catalysts. Quaternary ammonium salts of different alkyl group (C 3, C 4, C 6 and C 8) and anions (Cl −, Br − and I −) were used for this reaction carried out in a batch autoclave reactor at 60–120 °C. The catalytic activity increased with increasing alkyl chain length in the order of C 3 < C 4 < C 6. But, the quaternary ammonium salt with longer alkyl chain length (C 8) decreased the conversion of BGE because it is too bulky to form an intermediate with BGE. For the counter anion of the tetrabutyl ammonium salt catalysts, the BGE conversion decreased in the order Cl − > Br − > I −. The effects of carbon dioxide pressure and reaction temperature on this reaction were also studied to better understand the reaction mechanism.

Influence of Alkyl Chain Length on Phosphate Self-Assembled Monolayers

A series of alkyl phosphates with alkyl chain lengths ranging from C10 to C18 have been synthesized. Self-assembled monolayers (SAMs) of these molecules were prepared on titanium oxide surfaces by immersion of the substrates in alkyl phosphate solutions of 0.5 mM concentration in n-heptane/isopropanol. The SAMs were characterized by means of dynamic water contact angle (dCA) measurements, variable-angle spectroscopic ellipsometry (VASE), X-ray photoelectron spectroscopy (XPS), and polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS). A higher degree of order and packing density within the monolayers was found for alkyl phosphates with alkyl chain lengths exceeding 15 carbon atoms. This is reflected in a lower dCA hysteresis, as well as a film thickness measured by VASE and XPS close to the expected values for SAMs with an average alkyl chain tilt angle of 30 degrees to the surface normal. Additionally a shift of the symmetric and antisymmetric C-H stretching modes in the PM-IRRAS spectra to lower wave numbers was observed. These findings imply a higher two-dimensional crystallinity of the films derived from alkyl phosphates with a longer alkyl chain length.

Effects of imidazolium salts as cocatalysts on the copolymerization of CO 2 with epoxides catalyzed by (salen)Cr IIICl complex

Imidazolium salts, most of which are room temperature ionic liquids (ILs), have been introduced as effective and tunable cocatalysts in the copolymerization of CO 2 with epoxides catalyzed by (salen)Cr IIICl complex for the first time. Effects of imidazolium salts with different alkyl chains as well as with different anions on the copolymerization were investigated. The results showed that the copolymerization was influenced obviously by the property of anion. In addition, the cation of imidazolium salts with longer alkyl chain length such as n-dodecyl (TOF, 242.5 h −1, carbonate linkages > 99%) displays better activities and selectivity in the copolymerization as compared with N-MeIm (TOF, 72.5 h −1, carbonate linkages 94%). These results are instructive for further design of task-specific ILs as effective cocatalysts to improve the copolymerization of CO 2 with epoxides.

Thermodynamics of micelle formation of alkyltrimethylammonium chlorides from high performance electric conductivity measurements

Understanding micelle formation requires its complete thermodynamic characterization. In this work micellization of the model ionic surfactants decyltrimethylammonium chloride (DETAC), dodecyltrimethylammonium chloride (DTAC) and tetradecyltrimethylammonium chloride (TTAC) was investigated by high performance conductivity measurements, using instrumentation developed in our laboratory. The temperature dependence of the critical micelle concentration exhibits a minimum characterized by Δ mic H 0 = 0 (endothermic to exothermic process) and the degree of micelle ionization increases slightly with increasing temperature. The temperature change of Δ mic S 0 indicates that the process of micellization is entropically driven. Δ mic G 0 is always negative and slightly temperature dependent. The temperature dependence of the thermodynamic parameters is discussed in terms of the alkyl chain length and nature of the counterion. The micellization process is more favourable for surfactants with longer alkyl chain length and larger (less hydrated) counterions.

Pore-expansion of monodisperse mesoporous silica spheres by a novel surfactant exchange method

By adapting a novel surfactant exchange method, in which surfactants inside mesopores are completely exchanged by surfactants with longer alkyl chain lengths, pore-expansion of monodisperse mesoporous silica spheres (MMSS) with radially ordered hexagonal regularity was attained while retaining spherical morphology and high monodispersity.

Decomposition of tetraalkylammonium thiotungstates characterized by thermoanalysis, mass spectrometry, X-ray diffractometry and scanning electron microscopy

Thermal decomposition reactions of tetraalkylammonium thiotungstates, (R 4N) 2WS 4 (R = methyl to heptyl), were investigated with DSC and DTA–TG coupled with mass spectroscopy (MS). The results demonstrate that the complexity of thermal decomposition reactions is significantly influenced by the alkyl group, i.e., more complex steps are observed for the materials with longer alkyl chain lengths. Tetraethyl and tetrapropyl complexes show reversible and irreversible phase transitions detected by DSC experiments combined with thermodiffractometry. The tetrapentyl compound undergoes an irreversible phase transition while the tetraheptyl sample exhibits a glass-like transition and melting prior to decomposition. The whole series of compounds decompose without forming sulfur rich WS n ( n = 3 or 4) intermediates. The final WS 2 products are nearly stoichiometric for R = methyl to pentyl but for hexyl and heptyl samples the sulfur content is significantly reduced with a W/S ratio of about 1.5. The residual carbon and hydrogen contents increase in the final decomposition products in the same order as the number of C atoms in R 4N increase. For the N content no clear trend is obvious. A general thermal decomposition mechanism is suggested which follows a bimolecular nucleophilic substitution reaction. In the SEM images only for R = heptyl the formation of macro-pores with a sponge-like morphology is seen, but for the other precursors compact materials are formed which in part display a well developed morphology. X-ray diffraction analysis of the final products shows the formation of amorphous WS 2 up to the tetrapentyl precursor. But for the tetrahexyl and tetraheptyl materials the W:S ratio is significantly smaller than 1:2 and large amounts of C and H are determined by chemical analyses. In accordance with previously reported results it can be assumed that a carbosulfide phase is formed by a mixed C–W–S sandwich layered structure.

Biodegradability of imidazolium and pyridinium ionic liquids by an activated sludge microbial community

Ionic liquids (ILs) are novel organic salts that have enormous potential for industrial use as green replacements for harmful volatile organic solvents. Varying the cationic components can alter the chemical and physical properties of ILs, including solubility, to suit a variety of industrial processes. However, to complement designer engineering, it is crucial to proactively characterize the biological impacts of new chemicals, in order to fully define them as environmentally friendly. Before introduction of ILs into the environment, we performed an analysis of the biodegradability of six ILs by activated sludge microorganisms collected from the South Bend, Indiana wastewater treatment plant. We examined biodegradability of 1-butyl, 1-hexyl and 1-octyl derivatives of 3-methyl-imidazolium and 3-methyl-pyridinium bromide compounds using the standard Organisation for Economic Cooperation and Development dissolved organic carbon Die-Away Test, changes in total dissolved nitrogen concentrations, and 1H-nuclear magnetic resonance analysis of initial and final chemical structures. Further, we examined microbial community profiles throughout the incubation period using denaturing gradient gel electrophoresis (DNA-PCR-DGGE). Our results suggest that hexyl and octyl substituted pyridinium-based ILs can be fully mineralized, but that imidazolium-based ILs are only partially mineralized. Butyl substituted ILs with either cation, were not biodegradable. Biodegradation rates also increase with longer alkyl chain length, which may be related to enhanced selection of a microbial community. Finally, DGGE analysis suggests that certain microorganisms are enriched by ILs used as a carbon source. Based on these results, we suggest that further IL design and synthesis include pyridinium cations and longer alkyl substitutions for rapid biodegradability.

Performance of ionic liquid as catalyst in the copolymerization of phenyl glycidyl ether with carbon dioxide

The copolymerization of phenyl glycidyl ether (PGE) and carbon dioxide was performed using ionic liquid as catalyst in a semi-batch reaction with a continuous supply of carbon dioxide. 1-alkyl-3-methyl imidazolium salts of different alkyl group (C2, C4, C6, C8) and anions (Cl-, BF4-, PF6-) were used for this reaction carried out under constant pressure. All the 1-alkyl-3-methyl imidazolium chlorides showed very high carbonate content. The turnover number (TON) and average molecular weight of the copolymer were affected by the structure of the imidazolium salt ionic liquid; the one with the cation of longer alkyl chain length and with more nucleophilic anion showed better reactivity. However, TON decreased when hexyl or octyl containing ionic liquids were used probably due to their steric hindrance. The effects of reaction temperature, carbon dioxide pressure, and reaction time on the carbonate content and TON of the polycarbonates are also discussed. Tetrabutylammonium chloride (TBAC) was also tested for this reaction to compare its catalytic performance with the ionic liquids.

Furostanol glycoside 26- O-β-glucosidase from the leaves of Solanum torvum

A β-glucosidase (torvosidase) was purified to homogeneity from the young leaves of Solanum torvum. The enzyme was highly specific for cleavage of the glucose unit attached to the C-26 hydroxyl of furostanol glycosides from the same plant, namely torvosides A and H. Purified torvosidase is a monomeric glycoprotein, with a native molecular weight of 87 kDa by gel filtration and a p I of 8.8 by native agarose IEF. Optimum pH of the enzyme for p-nitrophenyl-β-glucoside and torvoside H was 5.0. Kinetic studies showed that K m values for torvoside A (0.063 mM) and torvoside H (0.068 mM) were much lower than those for synthetic substrates, pNP-β-glucoside (1.03 mM) and 4-methylumbelliferyl-β-glucoside (0.78 mM). The enzyme showed strict specificity for the β- d-glucosyl bond when tested for glycone specificity. Torvosidase hydrolyses only torvosides and dalcochinin-8′-β-glucoside, which is the natural substrate of Thai rosewood β-glucosidase, but does not hydrolyse other natural substrates of the GH1 β-glucosidases or of the GH3 β-glucosidase families. Torvosidase also hydrolyses C 5–C 10 alkyl-β-glucosides, with a rate of hydrolysis increasing with longer alkyl chain length. The internal peptide sequence of Solanum β-glucosidase shows high similarity to the sequences of family GH3 glycosyl hydrolases.

Temperature Variation of DC Conductivity of Poly(3-alkyl Thiophenes) and Their Cocrystals

The dc conductivity of poly(3-alkyl thiophenes) (P3ATs) and their cocrystals are measured in the temperature range of -130 to 150 degrees C. Both solvent-cast films and the melt-cooled films are used. The former exhibit a sharp increase followed by a decrease in conductivity, whereas the latter show only a sigmoidal increase in conductivity with temperature. The sigmoidal increase of the melt-cooled samples is dependent on the regioregularity and alkyl chain length of the samples and is explained from the solid-state transformation of the interdigited type-II crystal to a noninterdigited type-I crystal. The type-I crystal itself has lower conductivity than type-II crystals, and the samples exhibit a blue shift in UV-vis absorption spectra with an increase in temperature. So the sigmoidal increase of conductivity is attributed to the increase in carrier mobility with temperature in the type-I crystals. The X-ray and DSC results suggest that during the transformation of type-II to type-I crystals with increasing temperature, localized crystallites of smaller dimensions separated by narrower amorphous portions are produced throughout the whole matrix. But in the type-II polymorph, the crystallites are large with a wider gap in between. The sigmoidal increase is attributed to the easier hopping of the charge carrier among the localized crystallites of the type-I crystal with increasing temperature. In the cocrystals, the smaller sigmoidal increase with increasing irregular sample concentration is valid for a lower concentration of such localized crystallites. The same is true for cocrystals with longer alkyl chain lengths. The interfibrillar contribution of conductivity through the network junctions together with the carrier hopping between the localized crystallites might be a possible reason for the metallic-type behavior of solvent-cast samples after a certain temperature. The melt-cooled films do not exhibit metallic-type behavior because of the absence of a fibrillar network morphology.

Ferroelectric liquid crystals with a thioester linking group positioned at the chiral tail

A homologous series of chiral thioesters, hexyl (2S)-2-[6-(4-alkanoyloxyphenyl)benzoyloxy-2′-naphthyl]thiopropionates, HnPBNTP (n=7–11) was synthesized, and the mesophases and electro-optical properties were studied. All the materials possess a ferroelectric SmC* phase, which was confirmed by the switching current behaviour. It was found that compounds with a shorter alkyl chain length (n=7–9) displayed SmA* and SmC* phases, while, compounds with a longer alkyl chain length (n=10 and 11), displayed the SmC* phase exclusively. Spontaneous polarization and apparent tilt angle were also measured. The maximum P s values are in the range 15–26 nC cm−2, and the maximum θ values are in the range 23°–28°.

Comparative investigation of structure characteristics of mixed β-lactoglobulin and different chain-length phophatidylcholine monolayer at the air/water interface

The dynamic adsorption and penetration characteristics of β-lactoglobulin into the monolayer of two different chain-length phosphatidylcholines (DSPC, DPPC) are systematically investigated using Brewster angle microscopy (BAM), fluorescence microscopy (FM) and film balance technique. It was found that all the two phosphatidylcholines can form stable complex films with the β-lactoglobulin. In the complex system of DPPC or DSPC/β-lactoglobulin the lipid domains were observed again owing to the penetration of the protein. With the increase of surface pressure, the stripe and block domains appeared and gradually turned brighter. It has been considered that protein is squeezed out from the lipid monolayer and aggregated at interface. The critical surface pressure of the β-lactoglobulin separated from DPPC or DSPC phase is increased when lipid has longer alkyl chain length. Therefore, the hydrophobic effect can be considered as a main factor to lead to the formation of a stabilized mixed lipid/protein film.

Multivariate correlation and prediction of the synthesis of vanadium substituted mesoporous molecular sieves

Vanadium substituted mesoporous molecular sieves (V-MCM-41) were prepared following a synthesis procedure developed in our laboratory [J. Phys. Chem. B 106 (2002) 8437]. N 2 adsorption and X-ray diffraction experimental results show that our samples have a highly ordered hexagonal structure and fairly good stability. X-ray absorption and UV–vis spectra provide strong evidence that most vanadium ions are incorporated into the framework of siliceous MCM-41. The most important variable properties are the structural order, pore diameter, and vanadium loading which can be controlled easily by changing synthesis variables in such a way that collapse of the V-MCM-41 structure does not occur. A more quantitative model was built to correlate the structure, pore size, and vanadium content with the main synthesis variables and their cross terms. Modeling results show that our models are reasonably good at predicting the structure and pore diameter, it also can predict vanadium loading content well with longer alkyl chain length.

Synthesis of photopolymers with pendant cyclic carbonate and cinnamic ester groups

Photopolymers with both pendant cyclic carbonate groups and cinnamic ester groups were synthesized by the addition reaction of poly(glycidyl methacryalte-co-styrene)[poly(GMA-co-AN)] with carbon dioxide and then with cinnamoyl chloride. Soluble quaternary ammonium salt catalysts showed good yield of cinnamoyl chloride addition to the glycidyl methacrylate groups. Quaternary salt catalysts of longer alkyl chain length and of more nucleophilic anion offered higher yield of cinnamoyl chloride addition. Photochemical reaction test showed that poly(CNMA-co-DOMA-co-St) had a good photosensitivity.

Monitoring von linearem Alkylbenzolsulfonat (LAS) in Deutschland/ Linear alkylbenzenesulphonate (LAS) monitoring in Germany

Several 7-day studies for LAS monitoring were carried out at five representative rivers and five corresponding sewage treatment plants (STP). The monitoring period started at August 31st and ended at October 27th, 1993. The mean LAS concentrations in the STP-influents were 3.3 mg/l (s = 1.6) determined before the mechanical treatment. The mean concentrations in the effluent were 25 μg LAS/I (s = 19), except for the STP Heinersdorf (Chemnitz river). In the effluent of this STP with only mechanical sewage treatment the mean LAS concentration was 2260 μg/l. In the biological STPs the mean LAS biodegradation/elimination is 99.2 %. The mean LAS concentrations in the rivers (except for the Chemnitz river) were 3.3 μg/l (s = 2) upstream and 5 μg/l (s = 9) downstream. The mean values cover all LAS concentrations measured, without taking into account the different distances of the sampling points from the discharge points. The mean LAS concentrations in the Chemnitz river were 63 μg/l upstream and 570 μg/l (s = 75) downstream. Several 4 to 7-months monitoring studies for LAS adsorbed to suspended solids were carried out at the rivers Isar, Wupper and Chemnitz. The monitoring period started on march 1994 and ended on march 1995. The mean concentrations of LAS adsorbed to suspended solids (< 60 μm ) were 2 μg/g in the Isar river, 27 μg/g in the Wupper river and 73 μg/g in the Chemnitz river upstream of the sewage treatment plants Munchen II (Isar), Buchenhofen (Wupper) and Chemnitz-Heinersdorf (Chemnitz). The mean downstream concentrations of LAS adsorbed to suspended solids (< 60 μm) were 3 μg/g (Isar), 3 μg/g (Wupper) and 209 μg/g (Chemnitz). In average the amount of adsorbed LAS is less than 6 % of the total LAS in the water. Related to the organic matter of the suspended solids (< 60 μm) the amount of adsorbed LAS was 0.001 (Isar), 0.01 (Wupper) and 0.1 % (Chemnitz). The log K OM (partition coefficient related to the organic matter of the suspended solids (< 60 μm )) ranged from 3.4 to 4.3. LAS homologues with a longer alkyl chain length (C 12 , C 13 ) were adsorbed preferably.

Alkylbenzolsulfonat (LAS)-Monitoring

Several 4 to 7-months monitoring studies for LAS adsorbed to suspended solids were carried out at the rivers Isar Wupper and Chemnitz. The monitoring period started on march 1994 and ended on march 1995. The mean concentrations of LAS adsorbed to suspended solids (<60 μm) were 2 μg/g in the Isar river, 27 μg/g in the Wupper river and 73 μg/g in the Chemnitz river upstream of the sewage treatment plants Munchen II (Isar), Buchenhofen (Wupper) and Chemnitz-Heinersdorf (Chemnitz). The mean downstream concentrations of LAS adsorbed to suspended solids (<60 μm) were 3 μg/g (Isar), 13 μg/g (Wupper ) and 209 μg/g (Chemnitz). During the Monitoring exercise at the Chemnitz river biological sewage treatment plants did not exist throughout the whole region. In average the amount of adsorbed LAS is less than 6 % of the total LAS in the water body. Related to the organic matter of the suspended solids (<60 μm) the amount of adsorbed LAS was 0,001 (Isar), 0,01 (Wupper) and 0,1% (Chemnitz). The log K OM (partition coefficient related to the organic matter of the suspended solids (<60 μm) ranged from 3,4 to 4,3. LAS homologues with a longer alkyl chainlength (C12,C13) were adsorbed preferably.

Synthesis and ferroelectric properties of the thioester liquid crystals derived from (2S)-2-(6-hydroxy-2-naphthyl)propionic acid

Abstract A new homologous of chiral thioesters, hexyl (2S)-2-(6-(4-(alkoxyphenyl)benzoyloxy-2′-naphthyl)thiopropionates, HmPBNTP (m=8–14) has been synthesized for the study of mesomorphic and physical properties. All compounds are mesogenic and all mesophases are enantiotropic. Compounds with longer alkyl chain length (m–13 and 14) exhibit exclusive ferroelectric SC* phase, other compounds (m=8–12) possess SA and SC* phases. Novel ferrielectric SCγ* phase was found by the dielectric measurement. Depending on the alkyl chain length m, these chiral thioesters display three different phase transition sequences: I-SA-SC*-C, I-SA-SC*-SCγ*-C and I-SC*-SCγ *l-C. The magnitude of spontaneous polarization (Ps) and dielectric constant of the materials were also measured and reported.

Inhibition of rat liver cytochrome P450 isozymes by isothiocyanates and their conjugates: a structure-activity relationship study.

A series of arylalkyl and alkyl isothiocyanates, and their glutathione, cysteine, and N-acetylcysteine conjugates were used to study their inhibitory activity toward the dealkylation of ethoxyresorufin (EROD), pentoxyresorufin (PROD), and methoxyresorufin (MROD) in liver microsomes obtained from the 3-methylcholanthrene or phenobarbital-treated rats. These reactions are predominantly mediated by cytochrome P450 (P450) isozymes 1A1 and 1A2, 2B1 and 1A2, respectively. All isothiocyanates inhibited PROD more readily than EROD. Increases in the alkyl chain length of arylalkyl isothiocyanates to C6 resulted in an increased inhibitory potency in these assays; at longer alkyl chain lengths (C8-C10) the inhibitory potency declined. The IC50s for phenethyl isothiocyanate (PEITC) were 47, 46 and 1.8 microM for EROD, MROD and PROD, respectively. Substitution of an additional phenyl group on PEITC also increased the inhibitory potency; the IC50s for 1,2-diphenylethyl isothiocyanate (1,2-DPEITC) and 2,2-diphenylethyl isothiocyanate (2,2-DPEITC) were 0.9 and 0.26 microM for EROD, and 0.045 and 0.13 microM for PROD, respectively. The relative inhibitory potency of PEITC and its conjugates was N-acetylcysteine-PEITC (PEITC-NAC) < glutathione-PEITC (PEITC-GSH) < cysteine-PEITC (PEITC-CYS) < PEITC. The observations that the parent isothiocyanates were more potent inhibitors than the conjugates suggest that dissociation of the conjugate is required for activity. Naturally occurring alkyl isothiocyanates, sulforaphane (SFO) and allyl isothiocyanate (AITC), were very weak inhibitors in the assays. These results suggest the potential of isothiocyanates as structural probes for studying P450 isozymes. In addition, the inhibitory activity of isothiocyanates for PROD correlated with the previously demonstrated tumor inhibitory potency in (4-methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) induced A/J mouse lung tumor bioassays, which supports earlier findings that P450 2B1 is one of the major isozymes involved in NNK activation and that inhibition of this isozyme is an important mechanism for the chemopreventive activity of isothiocyanates.