Length Of Alkyl Substituent Research Articles

Solubility of CO 2 in imidazolium-based tetrafluoroborate ionic liquids

The solubility of CO 2 in imidazolium ionic liquids (ILs), 1-butyl-3-methyl imidazolium tetrafluoroborate ([bmim][BF 4]), 1-hexyl-3-methyl imidazolium tetrafluoroborate ([hmim][BF 4]) and 1-octyl-3-methyl imidazolium tetrtafluoroborate ([omim][BF 4]) was determined at 305–25 K and pressures from 1 to 9 MPa. The influence of chain length of alkyl substituents on the imidazolium cation on the solubility of CO 2 was investigated. The differences in solubility with chain length are in the sequence [omim][BF 4] > [hmim][BF 4] > [bmim][BF 4]. The solubility data were correlated by the extended Henry's law, and enthalpy, Gibbs free energy and entropy changes were obtained.

Phase transition and decomposition temperatures, heat capacities and viscosities of pyridinium ionic liquids

Ionic liquids are organic salts with low melting points. Many of these compounds are liquid at room temperature in their pure state. Since they have negligible vapor pressure and would not contribute to air pollution, they are being intensively investigated for a variety of applications, including as solvents for reactions and separations, as non-volatile electrolytes, and as heat transfer fluids. We present melting temperatures, glass transition temperatures, decomposition temperatures, heat capacities, and viscosities for a large series of pyridinium-based ionic liquids. For comparison, we include data for several imidazolium and quaternary ammonium salts. Many of the compounds do not crystallize, but form glasses at temperatures between 188 K and 223 K. The thermal stability is largely determined by the coordinating ability of the anion, with ionic liquids made with the least coordinating anions, like bis(trifluoromethylsulfonyl)imide, having the best thermal stability. In particular, dimethylaminopyridinium bis(trifluoromethylsulfonyl)imide salts have some of the best thermal stabilities of any ionic liquid compounds investigated to date. Heat capacities increase approximately linearly with increasing molar mass, which corresponds with increasing numbers of translational, vibrational, and rotational modes. Viscosities generally increase with increasing number and length of alkyl substituents on the cation, with the pyridinium salts typically being slightly more viscous than the equivalent imidazolium compounds.

Sorption equilibrium of Cr(VI) ions by strong base anion exchangers with pyridine structures

AbstractChromate sorption on pyridine strong base anion exchangers with different functional groups (methyl, ethyl, and butyl groups), at the quaternary nitrogen atoms, was studied as a function of various initial concentrations (100–1500 mg Cr/L) and counterion type. The studied resins in the Cl−[ form have higher Cr(VI)‐retention capacities than those in the SO form. The pyridine strong base anion exchangers showed a selectivity reversal for the sulfate and chromate anions compared to that of the commercial resins. The alkyl substituent length of the quaternary nitrogen atoms exerted a substantial influence on the Cr(VI)‐retention capacity values for the resins in the Cl− form; the chromate anions preferred resins with methyl functional groups, that is, resins with a greater hydrophilic structure. For the resins in the SO form the length of the substituent at the quaternary nitrogen atom had only a negligible influence on their Cr(VI)‐retention values. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1957–1963, 2004

Influence of the Structure of Nonionic Surfactants and the Length of Alkyl Substituents of Calix[4]resorcinarenes on Their Solubility, Acid–Base, and Complexation Properties

Regularities of solubilization of calix[4]resorcinarenes (H8L) with the variable length of hydrophobic radicals (R = CH3, C3H7, C5H11, C7H15, C8H17, C9H19, C11H23) by the micelles of nonionic surfactants Triton X-100 and Triton X-405 in aqueous solutions were studied using solubility measurements. It was found that the solubilization capacity of surfactant micelles with respect to H8L and [H4L]4– depends on the extension (thickness) of their polar layers. It was shown by means of potentiometric titration that, in solutions of nonionic surfactants, the constants of the interaction between tetraanions [H4L]4– and tetrametylammonium ions depend on the structure and concentration of nonionic surfactants and the hydrophobicity of H8L molecules. A change in the affinity of the [H4L]4– anions for protons and tetramethylammonium cations in nonionic surfactant solutions was revealed in relation to the length of substituents R and reagent concentrations.

Nonadiabatic electron transfer at the nanoscale tin-oxide semiconductor/aqueous solution interface.

Photo-excitation of chromophoric metal complexes electrostatically adsorbed to tin-oxide semiconductor nanoparticles is often accompanied by injection of electrons from the complexes into the semiconductor conduction band. The mechanism of back electron transfer (semiconductor particle to adsorbed molecule) for a family of tris-bipyridyl ruthenium and osmium complexes has been examined by evaluating the kinetics of transfer to derivatives featuring alkyl substituents of varying length, methyl to pentyl. The substituents serve to change the electron transfer (ET) distance under conditions of weak chemical interaction with the semiconductor surface. Accompanying increases in alkyl substituent length, and therefore transfer distance, are systematic decreases in back ET rate. The decreases are indicative of nonadiabatic ET, i.e. electronic rather than nuclear control of the reaction dynamics. Further analysis points to trap-mediated transfer, rather than direct transfer from the conduction band, as the most probable back-reaction pathway.

DNA compaction by divalent cations: structural specificity revealed by the potentiality of designed quaternary diammonium salts.

DNA interaction with quaternary diammonium dications, R(CH(3))(2)N(+)(CH(2))(n)N(+)(CH(3))(2)R, having various intercharge distances, lengths, and branching, and the chemical nature of the hydrophobic substituents were investigated by fluorescent microscopy and circular dichroism (CD) spectroscopy to reveal their structural specificity for binding to DNA. The conformational behavior of DNA was found to be highly sensitive to the structure of the dications with separated charges. The distance between two ammonium groups greatly influences the compaction activity of the dications. To explain this situation, we proposed a model that demonstrates that the charge density of the dication and the geometric fit between DNA phosphates and the ammonium groups in the dications play an important role in providing efficient DNA collapse. Elongation of the alkyl substituents (R) in the diammonium salts from ethyl to hexyl did not generate any significant alterations in the compaction activities, whereas the branching of substituents caused a drastic decrease in their compaction ability. Based on the results of CD spectroscopy, it was found that the ability of the dications to provoke a DNA transition from the B-form to A-form was also specific: it depended on their intercharge distances and was independent of the length of alkyl substituents.

Solid-state Photopolymerization of Diacetylene-containing Carboxylates with Naphthylmethylammonium as the Countercation in a Two-dimensional Array

Abstract Naphthylmethylammonium salts of a series of diacetylene-containing carboxylic acids with various sizes of alkyl chains were photopolymerized in the crystalline state. X-ray crystal structure analyses confirmed lamellar structures characterized with the two-dimensional hydrogen networks formed between carboxylate anion and countercation layers in the crystals. The absorption properties of the resulting polymers depended on the length of alkyl substituents.

Peroxynitrite flux-mediated LDL oxidation is inhibited by manganese porphyrins in the presence of uric acid.

We have studied the role of three Mn(III)porphyrins differing in charge, alkyl substituent length and reactivity, on LDL exposed to low fluxes of peroxynitrite (PN) in the presence of uric acid. Mn(III)porphyrins (5 microM, MnTE-2-PyP(5+), MnTnOct-2-PyP(5+), and MnTCPP(3-)) plus uric acid (300 microM) inhibited cholesteryl ester hydroperoxide formation, changes in REM as well as spared alpha- and gamma-tocopherol. MnTnOct-2-PyP(5+), the more lipophilic compound, was the most effective in protecting LDL lipids, while MnTCPP(3-) exerted the lesser protection. Mn(III)porphyrins react fast with PN ( approximately 10(5)-10(7) M(-1) s(-1)) to yield a O=Mn(IV) complex. The stoichiometry of uric acid consumption was approximately 1.7 moles per mol of PN, in agreement with reactions with both the O=Mn(IV) complex and nitrogen dioxide. A shift from an anti- to a pro-oxidant action of the Mn(III)porphyrin was observed after uric acid was significantly consumed, supporting competition reactions between LDL targets and uric acid for the O=Mn(IV) complex. Overall, the data is consistent with the catalytic reduction of PN in a cycle that involves a one electron oxidation of Mn(III) to Mn(IV) by PN followed by the reduction back to Mn(III) by uric acid. These antioxidant effects should predominate under in vivo conditions having plasma uric acid concentration range between 150 and 500 microM.

Comparative study of the electrochemical response of poly (alkyl thiophene) derivatives deposited on platinum and titanium electrodes

A comparative investigation of the electrochemical response of poly(alkyl thiophene) derivatives (3-methylthiophene and 3-octylthiophene) on two different electrode materials (platinum and titanium) was performed using cyclic voltammetry. By analyzing the voltammetric data, a slight potential shift of the oxido-reduction peaks in polyoctylthiophene film deposited on titanium electrode compared to platinum has been observed. The calculated surface concentrations of the electroactive centers were found to decrease significantly in poly(octylthiophene) grafted onto titanium surface, while in poly(methylthiophene) these changes were negligible. The influence of the nature of the electrode material and the alkyl substituent length on the redox properties has been discussed. The reduced forms of the synthesized polymer films were characterized by FTIR spectroscopy. The FTIR spectra indicate decrease of the conjugation length, the degree of polymerization and the presence of defects (2,4 linkages and C=O groups) with the increase of the alkyl group length.

Effect of pH and sodium chloride on the strength and selectivity of the interaction of τ-cyclodextrin with some antisense nucleosides

The influence of pH and the concentration of sodium chloride on the strength and selectivity of the interaction of twelve 8-substituted-2′-deoxyadenosine and sixteen 5-substituted-2′-deoxyuridine derivatives with gamma-cyclodextrin (GCD) have been studied by the spectral mapping technique (SPM). The potency values of the spectral map were regarded as indicators of the capability of antisense nucleosides and GCD to interact simultaneously taking into consideration all relevant data. It has been established that the strength of interaction is highest in acetic and lowest in alkaline solutions, and the selectivities of acidic, alkaline and salt solutions are markedly different. The length of hydrophobic alkyl substituents in antisense molecules influenced both the strength and selectivity of the interaction. The character of the base structure affected only the selectivity.

Effect of the composition of polysaccharides in gelatinized cornstarch on alcohol absorption

Sorption of alcohols in aqueous suspensions of gelatinized cornstarches with various contents of amylose was studied by capillary gas chromatography. Alcohol sorption depended primarily on the structure of alcohols, but not on the composition of polysaccharides. No correlation was found between the efficiency of sorption and amylose content in starch. The amount of substances sorbed by starches depended linearly on their initial concentration in the gel. Normal and highly amylose starches sorbed alcohols to a similar degree. However, increasing the length of alkyl substituents improved sorption of alcohols. Amylopectin starch differed in high affinity for small molecules and low sensitivity to the structure and hydrophobicity of alcohols.

Inhibition of copper amine oxidases by pyridine-derived aldoximes and ketoximes

The reactions of pea diamine oxidase (PSAO) and 2-phenylethylamine oxidase from Arthrobacter globiformis (AGAO) with pyridine-derived oximes were studied. Pyridine carbaldoximes and alkyl pyridyl ketoximes act as strong non-competitive inhibitors of the enzymes. The inhibition constants K i of these compounds vary between 10 -4 and 10 -5 M, for AGAO and some of the studied oximes were found even micromolar K i values. The presence of pyridine moiety in the studied compounds has remarkable influence on the inhibition potency. Elementary oximes lacking the heterocyclic ring, i.e., aliphatic (acetone oxime), alicyclic (cyclohexanone oxime) and aromatic (benzaldoxime), are considerably weaker non-competitive inhibitors ( K i ∼10 -3 or 10 -2 M). The position of the pyridine ring substitution by –C(R)=NOH group does not play a significant role for the inhibition potency of the studied oxime compounds. If the pyridine nitrogen is quaternised (in hydroxyiminomethyl-1-methylpyridinium iodides), the compound looses its inhibitory properties. Extended length of alkyl substituents on the ketoxime group of alkyl pyridyl ketoximes increases the K i value. The enzyme-bound copper represents one of possible target sites for pyridine-derived oxime inhibitors. The addition of an alkyl pyridyl ketoxime or a pyridine carbaldoxime to a native PSAO sample perturbs the absorption spectrum of the enzyme (by an absorption increase in the region 300–400 nm) that is not observed in the spectrum of reacted PSAO apoenzyme. However, an additional formation of hydrogen bonds with amino acid side-chains at the active site should be considered, namely for 3- and 4-substituted pyridine derivatives.

New Chiral Ether Derivatives of 2-Arylidene-p-Menthane-3-Ones as Components of Induced Ferroelectric Systems

New 2-arylidene-p-menthane-3-ones containing the ether bridging group in the arylidene fragment have been synthesized and studied as chiral dopants in ferroelectric liquid crystal mixtures. The ferroelectric properties of these compositions were compared with those for compositions including chiral dopants that do not contain any bridging group. The influence of bridging group and terminal alkyl substituent length in the dopant molecule on the ferroelectric parameters of systems studied is discussed.

Bile Acid Sequestrants Based on Cationic Dextran Hydrogel Microspheres. 2. Influence of the Length of Alkyl Substituents at the Amino Groups of the Sorbents on the Sorption of Bile Salts

Cationic dextran hydrogel microspheres with pendant quaternary ammonium groups having alkyl substituents (C2–C12) at quaternary nitrogen were synthesized. The in vitro sorption of sodium salts of four bile acids (glycocholic, cholic, taurocholic, and deoxycholic acids) with these hydrogels was studied as a function of substituent alkyl chain length and bile acid hydrophobicity. Sorption experiments were performed in phosphate buffer solutions (pH 7.4) containing one bile salt (individual sorption) or mixtures of several bile salts (competitive sorption). Parameters for individual sorption were calculated taking into consideration the stoichiometric and cooperative binding of bile salts to oppositely charged polymer hydrogels. The results show that the increase in the length of the alkyl chain of the substituent leads to an increase in both ionization constant K0 and overall stability constant of binding K, but decreases the cooperativity parameter u. The competitive sorption studies indicate that the hydrogels display a good affinity for both dihydroxylic and trihydroxylic bile salts. The molar ratio of maximum amounts bound for the two types of bile acid is 2 to 1, which is much lower than those reported for other cationic polymers recommended as bile acid sequestrants. The binding constants for the sorption of bile salts by some dextran hydrogels are 20–30 times higher than those obtained for cholestyramine under similar sorption conditions. © 2001 Wiley‐Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:681–689, 2001

Near-field scanning optical microscopy (NSOM) study of alkyl-substituted polyfluorene films: the affect of alkyl substituent length on nanoscale polymer ordering and cluster formation.

Pristine and Annealed 170 nm films of the stiff-chain polyfluorene, bearing two hexyl (1) or dodecyl (2) groups at the 9 position were studied using Near-field Scanning Optical Microscopy (NSOM). NSOM images reveal two distinct types of nanoscale film morphology: clusters and long-range order (LRO). Dual polarization and dual wavelength fluorescence collection schemes are combined with the use of simple image math provide both qualitative and quantitative characterization. In pristine films, shorter alkyl substituents (1) reduce the solubility of the polyfluorene in the spinning solution used for spin-coating films which leads to the formation of 50-150 nm clusters which are not present in films made from 2. Clusters can be removed by annealing as a function of time. Polarization shows the clusters are amorphous with fluorescence from both intra and inter-polymer species. The second variety of nanoscale ordering, LRO, is characterized by regions of polarized emission in the polymer films. This polarization can be quantified with an anisotropy value and is barely present in pristine films of 1 but increases dramatically upon annealing to induce a liquid crystalline phase transition. Pristine films of 2 have larger anisotropy values than pristine films of 1, due to longer alkyl-substituent-induced ordering during the spin-coating procedure, but films of 2 have only a slight increase in their anisotropy value upon annealing. Both intra and inter-polymer emitting species are distributed homogeneously throughout both pristine and annealed films within the resolution of our microscope (40-70 nm).

Synthesis and evaluation of cationic and cationogenic polymeric sorbents for removing surfactants from aqueous solutions

Polymers based on 2-dimethylaminoethyl methacrylate (DMAEMA) crosslinked with ethylene glycol dimethacrylate (EGDMA) or N,N'-methylenebisacrylamide (MBAA) have been prepared by solution-suspension polymerization. Polymers containing ammonium groups were synthesized by quaternization of aminofunctional polymers obtained with ethyl or dodecyl bromide or by the polymerization of respective quaternized monomers. Influence of the content of DMAEMA in the polymers, nominal degree of crosslinking, length of alkyl substituent in quaternary ammonium groups as well as particle size on the sorption of anionic and nonionic surfactants from aqueous solutions has been studied.

Effect of the synthesis temperature and the length of alkyl substituents on photoelectrical properties of polyterthiophenes

Three poly(4,4″-dipentoxy-3′-alkyl-2,2′:5′,2″-terthiophene)s with different lengths of the alkyl side-chains (dodecyl, octyl and hexyl) were prepared by cyclic voltammetry. The morphology of these polymers was found to be regular and to depend on the temperature of electrosynthesis. Better morphology was obtained in all cases for polymers prepared at somewhat higher temperatures (from 40 °C to 25 °C). The photoelectrical properties of the polymers were improved by decreasing the length of the alkyl side-chain. For the same alkyl chain length, better photoelectrical properties were found for polymers with a more regular morphology.

Selective Cleavage of the Two C-S Bonds in Asymmetrically Alkylated Dibenzothiophenes by Rhodococcus erythropolis KA2-5-1.

The Rhodococcus erythropolis strain KA2-5-1 was characterized by its ability to cleave carbon-sulfur bonds in the dibenzothiophene (DBT) ring by asymmetrically alkyl substitution, such as C2-DBTs (e.g., dimethyl and ethyl DBTs) and C3-DBTs (e.g., trimethyl and propyl DBTs), which are known to remain in hydrodesulfurization-treated diesel fuels. After treatment by solid-phase extraction (SPE) of solvents from microbial reactions of alkylated DBTs (Cx-DBTs), we used gas chromatography (GC), GC-atomic emission detection, GC-mass spectrometry and 1H nuclear magnetic resonance spectroscopy to identify and quantitatively evaluate the Cx-DBT metabolites. Molar ratios of metabolic isomers of the desulfurization products suggested that resting-cell reactions of KA2-5-1 against these Cx-DBTs occurrs through specific carbon-sulfur-bond-targeted cleavages, yielding alkylated hydroxybiphenyls, and that the manner of the attack on the DBT skeleton is affected not only by the position but also by the number and length of the alkyl substituents.

Effect of chain length and ring size of alkyl and cycloalkyl side-chain substituents upon the biological activity of brassinosteroids. Preparation of novel analogues with activity exceeding that of brassinolide.

A series of brassinosteroids with different alkyl or cycloalkyl substituents in place of the isopropyl group at C-24 of brassinolide (1) were prepared by the CuCN-catalyzed addition of Grignard reagents to (threo-2R,3S,5alpha,22R,23R,24S)-23,24-epoxy-6, 6-(ethylenedioxy)-2,3-(isopropylidenedioxy)-26, 27-dinorcholestan-22-ol (9), followed by deketalization and Baeyer-Villiger oxidation. Compound 9 was employed as part of a 70:30 threo/erythro mixture of epoxides 9 and 10, from which the erythro-epoxide 10 was recovered intact after the Grignard additions. Thus, the corresponding n-dodecyl, n-hexyl, n-propyl, tert-butyl, cyclohexyl, cyclopentyl, cyclobutyl, and cyclopropyl analogues of brassinolide were obtained. A rearrangement byproduct was observed during the preparation of the cyclopropyl-substituted brassinosteroid when ether was used as the solvent in the Grignard reaction, but could be avoided by the use of THF. A method for recycling the undesired erythro-epoxide 10 was developed on the basis of deoxygenation with tellurium and lithium triethylborohydride. The rice leaf lamina inclination assay was then used to measure the bioactivity of the products. In general, increasing activity was observed as the length or ring size of the C-24 hydrocarbon substituent decreased. The novel cyclobutyl- and cyclopropyl-substituted analogues of brassinolide (1) were ca. 5-7 times as active as 1 and thus appear to be the most potent brassinosteroids reported to date. Further enhancement of the bioactivity of all of the above brassinosteroids, except that of the inactive n-dodecyl derivative, was observed when the brassinosteroid was applied together with an auxin, indole-3-acetic acid (IAA). The synergy between the brassinosteroids and IAA thus increased the bioactivity of the brassinosteroids, including the cyclopropyl and cyclobutyl derivatives, by ca. 1-2 orders of magnitude.

Sorption of aliphatic alcohols from aqueous solutions by starch cryotextures

Capillary gas chromatography was applied to study the sorption of aliphatic ketones (C6—C11), including metamers, from aqueous solutions by corn starch cryotextures. The amount of ketones sorbed by cryotextures depends linearly on their concentrations in the initial sol. Equations describing the concentration dependence of sorption were proposed. The shape of sorption isotherms reflects the strength of sorption. The binding constants and the number of binding sites were determined for weakly sorbed ketones. The length of alkyl substituent and the position of the functional group are the crucial factors governing the sorption of ketones under conditions of excess binding sites. It was found that the degree of sorption increases with an increase in the carbon chain length from 6 to 9 carbon atoms. The presence of cooperation of binding sites for ketone sorption by cryotextures was demonstrated. The major part of ketones is sorbed irreversibly. This fact points to the formation of supramolecular complexes. Ketones with lower molecular masses are better sorbed by cryotextures than by native starch grains.