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Equimolar Mixture (equimolar + mixture)
Selected AbstractsAb Initio Molecular Dynamics Simulation of a Water,Hydrogen Fluoride Equimolar MixtureCHEMPHYSCHEM, Issue 1 2005Christian Simon Abstract Hydrogen fluoride and water can be mixed in any proportion. The resulting solutions have unique acidic properties. In particular, hydrogen fluoride undergoes a weak-to-strong acidity transition with increasing concentration of HF. To supplement the knowledge already obtained on dilute or moderately concentrated solutions and gas-phase aggregates, an equimolar mixture is studied here by Car,Parrinello molecular dynamics. The natures of the ions and of the complexes formed in the equimolar liquid were determined. Specifically, H3O+, H5O2+, FHOH2, and HF2,were spontaneously obtained while only hydronium and fluoride ions pre-exist in the equimolar crystal. The behaviour of the proton in the equimolar liquid was compared with mixtures of other proportions simulated previously in an attempt to relate proton dynamics to acidity. In the same way, the behaviour of HF2,was also examined. In this case, proton localization and transfer appeared to be driven by the fluctuating environment of the solvated ion. [source] Dielectric study of equimolar acetaminophen,aspirin, acetaminophen,quinidine, and benzoic acid,progesterone molecular alloys in the glass and ultraviscous states and their relevance to solubility and stabilityJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2010G.P. Johari Abstract Equimolar mixtures of acetaminophen,aspirin, acetaminophen,quinidine, and benzoic acid,progesterone have been vitrified and dielectric properties of their glassy and ultraviscous alloys have been studied. For 20,K/min heating rate, their Tgs are 266, 330, and 263,K, respectively. The relaxation has an asymmetric distribution of times, and the distribution parameter increases with increase in temperature. The dielectric relaxation time varies with T according to the Vogel,Fulcher,Tammann equation, log10(,0),=,AVFT,+,[BVFT/(T,,,T0)], where AVFT, BVFT, and T0 are empirical constants. The equilibrium permittivity is highest for the aspirin,acetaminophen and lowest for the benzoic acid-progesterone alloy, indicating a substantial interpharmaceutical hydrogen bonding that makes the alloy more stable against crystallization than the pure components. The benzoic acid,progesterone alloy is thermodynamically the most nonideal. It showed cold crystallization on heating, which is attributed to its relatively greater magnitude of the JG relaxation in relation to its ,-relaxation. It is argued that the difference between the free energy of an alloy and the pure components would have an effect on the solubility. Studies of solution thermodynamics of a glassy molecular alloy may be useful for optimizing choice of components and composition to form molecular alloys and to impact drug delivery. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 1358,1374, 2010 [source] Columnar liquid-crystalline assemblies composed of spiropyran derivatives and sulfonic acids,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10 2008Boon-Hooi Tan Abstract A series of fan-shaped spiropyran derivatives with different length of alkyl chains has been synthesized. Liquid-crystalline (LC) assemblies of spiropyran derivatives have been formed by the addition of organic sulfonic acids such as trifluoromethylsulfonic acid, 10-camphorsulfonic acid, 4-methylbenzenesulfonic acid, and imidazolium-based ionic liquids (ILs) having a sulfonic acid group. Equimolar mixtures of a fan-shaped spiropyran derivative with the acidic imidazolium-based ILs exhibit columnar phases with wider LC temperature ranges as compared to those of other mixtures. The ionic interactions formed by the ionic imidazolium moieties should contribute to the stabilization of the columnar phases. On the other hand, equimolar mixtures of the spiropyran derivative with decane-1-sulfonic acid having a long alkyl chain and poly(4-styrenesulfonic acid) do not show mesomorphism. The chemical structure of organic sulfonic acids is a key factor for the induction and stabilization of the LC phases. Copyright © 2008 John Wiley & Sons, Ltd. [source] Planar packing of tetrachlorodicyanobenzenes.ACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2009Equimolar mixtures of ortho - and meta -, or ortho - and para -, or meta - and para -tetrachlorodicyanobenzene, C6Cl4(CN)2, form structures with disordered layers containing both kinds of molecules in rhombohedral or pseudo-rhombohedral cells. These structures are similar to the structure of the rhombohedral form of the meta isomer. The guiding force appears to be an intermolecular synthon, in which a nitrile group in one molecule interacts with Cl atoms in two adjacent molecules with N...Cl distances of approximately 3.1,Å. [source] Dehydrogenation of Hydridoirida-,-diketones in Methanol: The Selective Formation of Mono- and Dinuclear Acyl ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2010Roberto Ciganda Abstract The hydridoirida-,-diketone [IrH{(PPh2(o -C6H4CO))2H}Cl] (1) reacts with diimines (NN) or with pyridine (py) in refluxing methanol to undergo dehydrogenation. The reactions afford selectively the cis -acyl, trans -phosphane isomers of the cationic [Ir(PPh2(o -C6H4CO))2(NN)]+ {NN = 2,2,-bipyridine (2); R,N=C(CH3),C(CH3)=N,R, [R = R, = NH2 (3); R = R, = OH (4); R = OH, R, = NH2 (5)]} or neutral [IrCl(PPh2(o -C6H4CO))2(py)] (6) derivatives. The reactions are faster for ligands containing amino substituents. Refluxing 1 in MeOH affords the formation of an equimolar mixture of dimercationic species [Ir2(,-Cl)(,-PPh2(o -C6H4CO))2(PPh2(o -C6H4CO))2]+ (7a and 7b) containing two acyls and a chloride as bridging groups. The isomers could be separated by fractional precipitation. Compound [3]Cl, containing amino substituents in the imino functionalities, catalyses the hydrogen transfer from 2-propanol to cyclohexanone to afford cyclohexanol. All the complexes were fully characterised spectroscopically. Single crystal X-ray diffraction analysis was performed on complexes 6 and [7b]ClO4. [source] Synthesis, Structure and Chemical Transformations of EthynylgermatranesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2003Edmunds Lukevics Abstract Ethynylgermatranes have been prepared from monosubstituted acetylenes by a three-step synthesis without isolation of the hydrolytically unstable intermediate chlorogermanes and ethoxygermanes. Boiling an equimolar mixture of tetrachlorogermane Cl4Ge, acetylene RC,CH and triethylamine in hexane leads to germylation of the Csp,H bond and the formation of ethynyl-substituted trichlorogermanes. Subsequent alkoxylation of chlorogermanes by ethanol in the presence of triethylamine affords triethoxygermanes that then take part in transalkoxylation with triethanolamine to give ethynylgermatranes. The molecular structures of all ethynylgermatranes and the hexacarbonyldicobalt complex of 1-heptynylgermatrane have been determined by X-ray crystallography. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Effects of NO2, CO, O2, and SO2 on oxidation kinetics of NO over Pt-WO3/TiO2 catalyst for fast selective catalytic reduction processINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 10 2006Muhammad Faisal Irfan The selective catalytic reduction rate of NO with N-containing reducing agents can be enhanced considerably by converting a part of NO into NO2. The enhanced reaction rate is more pronounced at lower temperatures by using an equimolar mixture of NO and NO2. The kinetics of NO oxidation over Pt-WO3/TiO2 catalyst has been determined in a fixed-bed reactor with different concentrations of oxygen, nitric oxide, and nitrogen dioxide in the presence of 8% water. It has been found that the reaction is second order with respect to nitric oxide, first order for oxygen with a third-order rate constant. Also, it is found that there is no effect on the reaction order with an addition of NO2, CO, or SO2. It follows the same second order but the reaction rate is found to be changed. It is observed that in the case of NO2 and SO2, the reaction rate tends to decrease, but it increases with the addition of CO into the feed. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 613,620, 2006 [source] Propylene/propane separation by vacuum swing adsorption using 13X zeoliteAICHE JOURNAL, Issue 2 2001Francisco A. Da Silva A vacuum swing adsorption process using 13X zeolite pellets with five steps was designed to split an equimolar mixture of propylene/propane: pressurization with feed; high-pressure feed; high-pressure purge with product; cocurrent blowdown; and counter-current vacuum blowdown, where the enriched propylene product is withdrawn. In the process, the partial pressure of the C3 -mixture is controlled with nitrogen, which is used as inert gas. With an equimolar feed of C3 diluted to 50% with nitrogen, the column is fed at 5 bar and 423 K, and the product is obtained when the total pressure is lowered to 0.1 bar. After 15,20 cycles, the cyclic steady-state condition is achieved, a propylene-enriched stream of 98% mol relative to propylene/propane mixture, with 3.2% of nitrogen, a recovery of 19% (molar basis), and a productivity of 0.785 mol/kg·h is obtained. The experimental work was complemented with numerical simulations, and the effect of different operating parameters on the performance of the VSA was considered. [source] Modification of polycondensation of isophthalic and terephthalic acids and bisphenols with tosyl chloride/dimethylformamide/pyridine by the presence of additivesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2003Fukuji Higashi Abstract In copolycondensation with 2,2-bis(4-hydroxyphenyl)propane (BPP) and bisphenols (BPs) containing various alkylidene linkages, the associative interactions between BP moieties in the resulting oligomers most likely affected the reaction. To modify the interactions to favorably control the reaction, several additives were examined in a two-stage polycondensation of an equimolar mixture of isophthalic acid and terephthalic acid, first with BPP (50 mol %) and next with additional BPP. Of additives used, diphenylmethane of an equivalent to BPP in the preformed oligomers was most effective. The results are discussed in terms of the distributions of resulting oligomers prepared at 70% extent of reaction. Better results were obtained when the distributions showed profiles similar to the theoretical one calculated on the basis that the reactivity of the oligomers is the same independent of their chain lengths. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 970,975, 2003 [source] Facile Synthesis of Polyaniline-Polypyrrole Nanofibers for Application in Chemical Deposition of Metal NanoparticlesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 16 2008Ping Xu Abstract Polyaniline-polypyrrole (PANI-PPy) nanofibers with high aspect ratios have been synthesized by a one-step, surfactant-assisted chemical oxidative polymerization from mixtures of aniline (An) and pyrrole (Py) monomers. PANI-PPy nanofibers synthesized with an excess of either PANI or PPy show similar spectral (UV-vis and FT-IR) characteristics as the individual homopolymers, whereas nanofibers from an equimolar mixture of An and Py display unique spectral characteristics. PANI-PPy nanofibers undergo a spontaneous redox reaction with metal ions to produce metal nanoparticles with various morphologies and/or sizes. These findings may open new opportunities for synthesizing functional polymer nanofibers and metal nanoparticles with controllable sizes and/or morphologies. [source] Response of workers of Atta sexdens rubropilosa (Hymenoptera: Formicidae) to mandibular gland compounds of virgin males and femalesPHYSIOLOGICAL ENTOMOLOGY, Issue 3 2007J. MAURÍCIO S. BENTO Abstract The secretion from the mandibular glands of males of the leaf-cutting ant Atta sexdens rubropilosa is responsible for the reaction of workers outside the nest at the time of sexual swarming. Workers respond with excitability and aggression when presented with the natural mixture of 4-methyl-3-heptanol and 4-methyl-3-heptanone, which is contained in the secretion of the male mandibular glands. Workers respond quickly to fractional amounts of one male equivalent. 4-Methyl-3-heptanone, from the virgin female mandibular glands causes much less response in workers, whereas an equimolar mixture of male and female pheromones gives a still less clear response. The male pheromone plays the most important part in the communication of workers outside the nest at this time. [source] Precursor ion scan profiles of acylcarnitines by atmospheric pressure thermal desorption chemical ionization tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2008Giuseppe Paglia The fatty acyl esters of L-carnitine (acylcarnitines) are useful biomarkers for the diagnosis of some inborn errors of metabolism analyzed by liquid chromatography/tandem mass spectrometry. In this study the acylcarnitines were analyzed by atmospheric pressure thermal desorption chemical ionization using a commercial tandem mass spectrometer (APTDCI-MS/MS). The method is based on the precursor ion scan mode determination of underivatized acylcarnitines desorbed from samples by a hot desolvation gas flow and ionized by a corona pin discharge. During desorption/ionization step the temperature induces the degradation of acylcarnitines; nevertheless, the common fragment to all acylcarnitines [MH,59]+ is useful for analyzing their profile. APTDCI parameters, including angle of collection and incidence, gas flows and temperatures, were optimized for acylcarnitines. The experiments were performed drying 2,µL of an equimolar mixture of acylcarnitine standards on a glass slide. The specificity was evaluated by comparing product ion spectra and the precursor ion spectra of 85 m/z of acylcarnitines obtained by the APTDCI method and by electrospray ionization flow injection analysis (ESI-FIA). The method was also employed to analyze acylcarnitines extracted from a pathological dried blood spot and a control. The method enables analysis of biological samples and recognition of some acylcarnitines that are diagnostic markers of inherited metabolic diseases. The intrinsic high-throughput analysis of the ambient desorption ionization methods offers a new opportunity either for its potential application in clinical chemistry and for the expanded screening of some inborn errors of metabolism. Copyright © 2008 John Wiley & Sons, Ltd. [source] [(NHC)AuI]-Catalyzed Formation of Conjugated Enones and Enals: An Experimental and Computational StudyCHEMISTRY - A EUROPEAN JOURNAL, Issue 22 2007Nicolas Marion Abstract The [(NHC)AuI]-catalyzed (NHC = N-heterocyclic carbene) formation of ,,,-unsaturated carbonyl compounds (enones and enals) from propargylic acetates is described. The reactions occur at 60,°C in 8,h in the presence of an equimolar mixture of [(NHC)AuCl] and AgSbF6 and produce conjugated enones and enals in high yields. Optimization studies revealed that the reaction is sensitive to the solvent, the NHC, and, to a lesser extent, to the silver salt employed, leading to the use of [(ItBu)AuCl]/AgSbF6 in THF as an efficient catalytic system. This transformation proved to have a broad scope, enabling the stereoselective formation of (E)-enones and -enals with great structural diversity. The effect of substitution at the propargylic and acetylenic positions has been investigated, as well as the effect of aryl substitution on the formation of cinnamyl ketones. The presence or absence of water in the reaction mixture was found to be crucial. From the same phenylpropargyl acetates, anhydrous conditions led to the formation of indene compounds via a tandem [3,3] sigmatropic rearrangement/intramolecular hydroarylation process, whereas simply adding water to the reaction mixture produced enone derivatives cleanly. Several mechanistic hypotheses, including the hydrolysis of an allenol ester intermediate and SN2, addition of water, were examined to gain an insight into this transformation. Mechanistic investigations and computational studies support [(NHC)AuOH], produced in situ from [(NHC)AuSbF6] and H2O, instead of cationic [(NHC)AuSbF6] as the catalytically active species. Based on DFT calculations performed at the B3LYP level of theory, a full catalytic cycle featuring an unprecedented transfer of the OH moiety bound to the gold center to the CC bond leading to the formation of a gold,allenolate is proposed. Es descriu la reacció de formació de compostos de carbonil ,,, -insaturats (enones i enals) a partir d,acetats propargílics catalitzada per [(NHC)AuI] (NHC=carbè N-heterocíclic). Les reaccions tenen lloc a 60,°C en 8,h en presència d,una mescla equimolar de [(NHC)AuCl] i AgSbF6 i produeix rendiments alts d,enones i enals conjugats. Estudis d,optimització van mostrar que la reacció era sensible al solvent, el NHC, i, en menor grau, a la natura de la sal de plata emprada; això va portar a escollir [(ItBu)AuCl]/AgSbF6 en THF com a sistema catalític eficient. La transformació va mostrar posseir un ampli espectre, i es va aconseguir la formació estereoselectiva d,(E)-enones i -enals amb gran diversitat estructural. La influència de la substitució en les posicions propargílica i acetilènica va ser investigada, així com la substitució d,aril per donar lloc a la formació de cinamilcetones. La presència o absència d,aigua en el medi de reacció es va mostrar com a crucial. A partir dels mateixos fenilpropargilacetats, condicions anhidres van portar a la formació de compostos indènics mitjançant una reacció tàndem de reorganització sigmatròpica [3,3] i hidroarilació intramolecular, mentre que l,addició d,aigua a la reacció portava de manera neta a derivats del tipus enona. Diverses hipòtesis mecanístiques, entre elles la hidròlisi d,un intermedi del tipus al.lenol ester i l,addició SN2, d,aigua, han estat examinades per millorar la comprensió del procés. Les dades mecanístiques i els estudis computacionals suggereixen que l,espècie catalítica activa és [(NHC)AuOH], produït in situ a partir de [(NHC)AuSbF6] i H2O, i no el complex catiònic [(NHC)AuSbF6]. A partir d,estudis DFT realitzats al nivell B3LYP, es proposa un cicle catalític complet, que inclou un nou tipus d,etapa consistent en la transferència d,un grup OH des de l,or cap a l,enllaç CC per produir un complex or-al.lenolat. [source] Toxicity and Synergism in the Feeding Deterrence of Some Coumarins on Spodoptera frugiperdaSmith (Lepidoptera: Noctuidae)CHEMISTRY & BIODIVERSITY, Issue 1 2006Nancy Vera Abstract The phagodepression activity of five coumarins (=2H -1-benzopyran-2-ones), 6-hydroxy-7-isoprenyloxycoumarin (1), 6-methoxy-7-isoprenyloxycoumarin (2), 6,7-methylenedioxycoumarin (3), 5-methoxy-6,7-methylenedioxycoumarin (4), and 6-methoxy-7-(2-hydroxyethoxy)coumarin (5), from the Argentine native herb Pterocaulon polystachyum, was tested against Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae. Two analogs, scopoletin (6) and 2-methoxy-2-methyl-3,4,5,6,7,8-hexahydro-3H -chromen-5-one (7), synthesized in our laboratory, were also evaluated for comparison. The compounds were added to an artificial diet at doses ranging from 50 to 200,,g per g of diet. Natural coumarins induced 100% of phagodepression when 200,,g were added per g of diet. Binary equimolar mixtures of the natural coumarins were phagodepressors against S. frugiperda surpassing the expected additive responses, indicating that these compounds can act synergistically against S. frugiperda larvae. Compounds 1 and 3 (non-methoxylated coumarins), and the equimolar mixture of both, displayed the strongest phagodepression. Additionally, 50,,g/g of 1 and 3 incorporated to the larval diet caused 80 and 50% of pupal mortality, respectively, while a 100,,g/g dose of compounds 2, 4, 6, and 7 produced 60, 50, 10, and 80% pupal mortality, respectively. Larval growing rate during the early larval instars was significantly reduced by treatments with the methylenedioxycoumarins 3 and 4. Coincidentally, the larval period duration was significantly increased by the latter compounds. [source] Ab Initio Molecular Dynamics Simulation of a Water,Hydrogen Fluoride Equimolar MixtureCHEMPHYSCHEM, Issue 1 2005Christian Simon Abstract Hydrogen fluoride and water can be mixed in any proportion. The resulting solutions have unique acidic properties. In particular, hydrogen fluoride undergoes a weak-to-strong acidity transition with increasing concentration of HF. To supplement the knowledge already obtained on dilute or moderately concentrated solutions and gas-phase aggregates, an equimolar mixture is studied here by Car,Parrinello molecular dynamics. The natures of the ions and of the complexes formed in the equimolar liquid were determined. Specifically, H3O+, H5O2+, FHOH2, and HF2,were spontaneously obtained while only hydronium and fluoride ions pre-exist in the equimolar crystal. The behaviour of the proton in the equimolar liquid was compared with mixtures of other proportions simulated previously in an attempt to relate proton dynamics to acidity. In the same way, the behaviour of HF2,was also examined. In this case, proton localization and transfer appeared to be driven by the fluctuating environment of the solvated ion. [source] Molecular analysis of mutations at the HPRT and TK loci of human lymphoblastoid cells after combined treatments with 3,-azido-3,-deoxythymidine and 2,,3,-dideoxyinosine,ENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 4 2002Quanxin Meng Abstract Combinations of antiretroviral drugs that include nucleoside reverse transcriptase inhibitors (NRTIs) are superior to single-agent regimens in treating or preventing HIV infection, but the potential long-term health hazards of these treatments in humans are uncertain. In earlier studies, our group found that coexposure of TK6 human lymphoblastoid cells to 3,-azido-2,,3,-dideoxythymidine (AZT) and 2,,3,-dideoxyinosine (ddI), the first two NRTIs approved by the FDA as antiretroviral drugs, produced multiplicative synergistic enhancement of DNA incorporation of AZT and mutagenic responses in both the HPRT and TK reporter genes, as compared with single-drug exposures (Meng Q et al. [2000a]: Proc Natl Acad Sci USA 97:12667,12671). The purpose of the current study was to characterize the mutational specificity of equimolar mixtures of 100 ,M or 300 ,M AZT + ddI at the HPRT and TK loci of exposed cells vs. unexposed control cells, and to compare the resulting mutational spectra data to those previously found in cells exposed to AZT alone (Sussman H et al. [1999]: Mutat Res 429:249,259; Meng Q et al. [2000b]: Toxicol Sci 54:322,329). Molecular analyses of HPRT mutant clones were performed by reverse transcription,mediated production of cDNA, PCR amplification, and cDNA sequencing to define small DNA alterations, followed by multiplex PCR amplification of genomic DNA to define the fractions of deletion events. TK mutants with complete gene deletions were distinguished by Southern blot analysis. The observed HPRT mutational categories included point mutations, microinsertions/microdeletions, splicing-error mutations, and macrodeletions including partial and complete gene deletions. The only significant difference or shift in the mutational spectra for NRTI-treated cells vs. control cells was the increase in the frequency of complete TK gene deletions following exposures (for 3 days) to 300 ,M AZT,ddI (P = 0.034, chi-square test of homogeneity); however, statistical analyses comparing the observed mutant fraction values (measured mutant frequency × percent of a class of mutation) between control and NRTI-treated cells for each class of mutation showed that the occurrences of complete gene deletions of both HPRT and TK were significantly elevated over background values (0.34 × 10,6 in HPRT and 6.0 × 10,6 in TK) at exposure levels of 100 ,M AZT,ddI (i.e., 1.94 × 10,6 in HPRT and 18.6 × 10,6 in TK) and 300 ,M AZT,ddI (i.e., 5.6 × 10,6 in HPRT and 34.6 × 10,6 in TK) (P < 0.05, Mann,Whitney U -statistic). These treatment-related increases in complete gene deletions were consistent with the spectra data for AZT alone (ibid.) and with the known mode of action of AZT and ddI as DNA chain terminators. In addition, cotreatments of ddI with AZT led to substantial absolute increases in the mutant fraction of other classes of mutations, unlike cells exposed solely to AZT [e.g., the frequency of point mutations among HPRT mutants was significantly increased by 130 and 323% over the background value (4.25 × 10,6) in cells exposed to 100 and 300 ,M AZT,ddI, respectively]. These results indicate that, at the same time that AZT,ddI potentiates therapeutic or prophylactic efficacy, the use of a second NRTI with AZT may confer a greater cancer risk, characterized by a spectrum of mutations that deviates from that produced solely by AZT. Environ. Mol. Mutagen. 39:282,295, 2002. Published 2002 Wiley-Liss, Inc. [source] Columnar liquid-crystalline assemblies composed of spiropyran derivatives and sulfonic acids,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10 2008Boon-Hooi Tan Abstract A series of fan-shaped spiropyran derivatives with different length of alkyl chains has been synthesized. Liquid-crystalline (LC) assemblies of spiropyran derivatives have been formed by the addition of organic sulfonic acids such as trifluoromethylsulfonic acid, 10-camphorsulfonic acid, 4-methylbenzenesulfonic acid, and imidazolium-based ionic liquids (ILs) having a sulfonic acid group. Equimolar mixtures of a fan-shaped spiropyran derivative with the acidic imidazolium-based ILs exhibit columnar phases with wider LC temperature ranges as compared to those of other mixtures. The ionic interactions formed by the ionic imidazolium moieties should contribute to the stabilization of the columnar phases. On the other hand, equimolar mixtures of the spiropyran derivative with decane-1-sulfonic acid having a long alkyl chain and poly(4-styrenesulfonic acid) do not show mesomorphism. The chemical structure of organic sulfonic acids is a key factor for the induction and stabilization of the LC phases. Copyright © 2008 John Wiley & Sons, Ltd. [source] Toxicity and Synergism in the Feeding Deterrence of Some Coumarins on Spodoptera frugiperdaSmith (Lepidoptera: Noctuidae)CHEMISTRY & BIODIVERSITY, Issue 1 2006Nancy Vera Abstract The phagodepression activity of five coumarins (=2H -1-benzopyran-2-ones), 6-hydroxy-7-isoprenyloxycoumarin (1), 6-methoxy-7-isoprenyloxycoumarin (2), 6,7-methylenedioxycoumarin (3), 5-methoxy-6,7-methylenedioxycoumarin (4), and 6-methoxy-7-(2-hydroxyethoxy)coumarin (5), from the Argentine native herb Pterocaulon polystachyum, was tested against Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae. Two analogs, scopoletin (6) and 2-methoxy-2-methyl-3,4,5,6,7,8-hexahydro-3H -chromen-5-one (7), synthesized in our laboratory, were also evaluated for comparison. The compounds were added to an artificial diet at doses ranging from 50 to 200,,g per g of diet. Natural coumarins induced 100% of phagodepression when 200,,g were added per g of diet. Binary equimolar mixtures of the natural coumarins were phagodepressors against S. frugiperda surpassing the expected additive responses, indicating that these compounds can act synergistically against S. frugiperda larvae. Compounds 1 and 3 (non-methoxylated coumarins), and the equimolar mixture of both, displayed the strongest phagodepression. Additionally, 50,,g/g of 1 and 3 incorporated to the larval diet caused 80 and 50% of pupal mortality, respectively, while a 100,,g/g dose of compounds 2, 4, 6, and 7 produced 60, 50, 10, and 80% pupal mortality, respectively. Larval growing rate during the early larval instars was significantly reduced by treatments with the methylenedioxycoumarins 3 and 4. Coincidentally, the larval period duration was significantly increased by the latter compounds. [source] | ||||||||||||||||