Carborane‐Derived Local Anesthetics are Isomer Dependent

Clinically there is a need for local anesthetics with a greater specificity of action on target cells and longer duration. We have synthesized a series of local anesthetic derivatives we call boronicaines in which the aromatic phenyl ring of lidocaine was replaced with ortho‐, meta‐, C,C’‐dimethyl meta‐ and para‐carborane clusters. The boronicaine derivatives were tested for their analgesic activity and compared with lidocaine using standard procedures in mice following a plantar injection. The compounds differed in their analgesic activity in the following order: ortho‐carborane = C,C’‐dimethyl meta‐carborane > para‐carborane > lidocaine > meta‐carborane derivative. Both ortho‐boronicaine and C,C’‐dimethyl meta‐boronicaine had longer durations of analgesia than lidocaine. Differences in analgesic efficacies are rationalized by variations in chemical structure and protein binding characteristics.     

Fabrication of the single-wall carbon nanotube compound polymer film electrode and the simultaneous electrochemical behavior of aminophenol isomers

We describe a simple, rapid and selective voltammetry for simultaneous determination of electroactive isomers using nanometer composite electrode. The electrode was constructed by electropolymerization of 4-aminopyridine at single-wall carbon nanotubes modified glassy carbon electrode (SWNTs/POAPE). The configuration and electrochemical properties of SWNTs/POAPE were characterized by scanning electronic micrographs (SEM) and voltammetry. The SWNTs/POAPE showed an excellent electrocatalytic activity to the oxidation of aminophenol isomers and capability of determining three aminophenol isomers simultaneously. The oxidation peak potential difference between m-aminophenol and o-aminophenol was 416 mV, o-aminophenol and p-aminophenol 119 mV, indicating that the o-, m- and p-aminophenol could be identified entirely at the SWNTs/POAPE. The proposed electrode has been applied to the simultaneous voltammetric determination of aminophenol isomers in mixture without previous chemical or physical separations.     

Comparative sorption kinetic studies of phenolic compounds on fly ash and impregnated fly ash

The factors affecting the rate processes involved in the removal of phenolic compounds, e.g. initial phenol concentration, particle size, impregnation of fly ash (IFA), pH and temperature have been studied. The removal rate of phenols varied in the order p-nitrophenol m-nitrophenol > o-nitrophenol > p-cresol > phenol > m-cresol > o-cresol. The process followed first order rate kinetics. The sorption data generally fit the Lagergren equation and the intraparticle diffusion rate equation from which adsorption rate constants, diffusion rate constants and diffusion coefficients were determined. Intraparticle diffusion was found to be the rate-limiting step. These kinetic parameters were compared for various phenols under different conditions using fly ash (FA) and impregnated fly ash (IFA).     

Processable heat-resistant polymers. XIII. Structure–property relationship in polyamideimides

Novel isomeric polyamideimides were synthesized by reacting the diacid chloride of 2-(4-carboxy phenyl)-1,3-dioxoisoindoline-5-carboxylic acid and o-, m-, and p-phenylenediamine at 30–70°C using polar solvents. The reactivity of the isomeric amines in the polycondensation reaction was studied. The isomeric effects on the physical, chemical, thermal, and electrical properties of the polymers were also studied. The polymers were found to be soluble in highly polar solvents such as DMF, DMAC, NMP, DMSO, m-cresol, etc. Thermal analysis indicated that polymers were thermostable and that their thermal stability follows the order para > meta > ortho. X-ray diffraction data revealed that para polymer is crystalline in nature. Dielectric properties with the variation of frequency at room temperature indicated that the dielectric constant and dielectric loss of the polymers follow the order ortho > meta > para.     

Electrochemical simultaneous determination of nitrophenol isomers at nano-gold modified glassy carbon electrode

A novel method for simultaneous determination of nitrophenol isomers at nano-gold modified glassy carbon electrode has been developed. The gold nanoparticles were directly electrodeposited onto the glassy carbon electrode via a constant potential −0.2 V (vs. SCE) for 60 s from 0.1 mol L⁻¹ KNO₃ containing 0.4 g L⁻¹ HAuCl₄. The resulting electrode (nano-Au/GCE) was characterized with scanning electron microscopy (SEM). The electrochemistry response of nitrophenol isomers at the nano-Au/GCE was studied. The result indicated that o-, m-, and p- nitrophenol are separated entirely at nano-Au/GCE, and a semi-derivative voltammetric technology was adopted to enhance the determination sensitivity. This modified electrode could be applied to direct simultaneous voltammetric determination of nitrophenol isomers in water samples without preseparation with higher sensitivity.     

Synthesis of polyguanamines from 2-N,N-dibutylamino-4,6-dichloro-1,3,5-triazine with aromatic diamines

Solution polycondensation of 2-N,N-dibutylamino-4,6-dichloro-1,3,5-triazine (BDCT) with various aromatic diamines, including 4,4′-oxydianiline (ODA), p-phenylenediamine (pPDA), m-phenylenediamine (mPDA), o-tolidine (oTD), 4,4′-(9-fluorenylidene)dianiline (BAFL), and 2,4-diamino-6-(N,N-dibutylamino)-1,3,5-triazine (DABT), was investigated. High molecular weight (>10,000) polyguanamines (PGs) were obtained via the polymerization of BDCT with ODA, pPDA, oTD, and BAFL at 150–180 °C in N-methylpyrrolidone (NMP) for 6 h. The polymerizability with BDCT was determined on the basis of the molecular weights of the polymers and the chemical shifts of the NMR data as follows: ODA > oTD > BAFL > pPDA > mPDA ? DABT. PGs were obtained from the reaction of BDCT with ODA and mPDA in only 55–77% yield, which may be attributed to the formation of cyclic oligomers. All of the polymers showed high thermostability (5% weight-loss temperature in N₂ greater than 444 °C), and the polymers generated from reaction of BDCT with ODA, mPDA, and BAFL exhibited good solubility in tetrahydrofuran and polar aprotic solvents such as NMP.     

Selective Liquid Phase Adsorption and Separation of ortho-Xylene with the Microporous MIL-53(Al)

Metal-organic framework MIL-53(Al) pellets were tested for the selective adsorption and separation of xylene isomers, in liquid phase and using n-heptane as eluent. The objective of this work is to assess relevant data for a posterior xylene isomers separation process design. In order to complete this study, single and multi-component breakthrough experiments were performed at 313 K, in the presence of n-heptane. MIL-53(Al) presented a preference for o-xylene over m-xylene and p-xylene in all experiments. The selectivities of 2.0 were obtained for o-xylene over m-xylene and over p-xylene. It is concluded that MIL-53(Al) may be used for separating o-xylene from the other xylene isomers, using n-heptane as desorbent. Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science & Technology to view the free supplemental file.     

Aromatic amine‐epoxidized sunflower free‐fatty‐acid adducts as corrosion inhibitors in epoxy‐curable varnishes

With strict regulation of environmental pollution, sunflower fatty acids were used to prepare high‐molecular‐weight aromatic amine adducts by reaction of their epoxidized form [epoxidized sunflower free fatty acid (ESFA)] with five aromatic amines [o‐toluidine (o‐T), m‐toluidine (m‐T), p‐toluidine (p‐T), p‐anizidine (p‐A), and p‐chloroaniline (p‐ClA)] under severe conditions of an inert atmosphere and high temperature. The produced adducts were characterized physically, chemically, and by IR spectroscopy. The acid values and oxirane contents of the prepared adducts were determined to confirm the participation of carboxylic groups and epoxy groups, respectively, in the reaction of ESFA with aromatic amines. Also, to avoid volatile organic compounds, the prepared adducts of ESFA (o‐T–ESFA, m‐T–ESFA, p‐T–ESFA, p‐A–ESFA, and p‐ClA–ESFA) were evaluated as corrosion inhibitors of mild steel in electron‐beam‐curable epoxy acrylate oligomer formulations. Physical and mechanical measurements were carried out, in addition to corrosion‐resistance tests and weight loss measurements of the coated steel panels. The optimum concentration of each adduct was determined for the prepared formulations. The corrosion‐inhibition efficiency of the adducts in varnish formulations were determined. It was found that varnish formulations containing the prepared aromatic amine adducts could protect steel from corrosion. The corrosion‐inhibition efficiencies of the prepared aromatic amines in epoxy acrylate oligomer varnishes were arranged as follows: p‐A–ESFA > p‐T–ESFA > m‐T–ESFA > o‐T–ESFA > p‐ClA–ESFA. Superior corrosion‐inhibition efficiency was obtained in the varnish formula containing 0.6% p‐A–ESFA adduct. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Adsorption Characteristics of Cresols with Eluent Composition in Adsorption Chromatography

Abstract

Adsorption characteristics of cresol isomers in adsorption chromatography were investigated in a system where the binary eluent containing ethyl acetate as a modifier in n?hexane was used. The method of moments was used to estimate the equilibrium constant and the rate parameters. The agreement between the experimental and theoretical results calculated by the orthogonal collocation method was excellent. The equilibrium constant and rate parameters for each cresol were empirically correlated with eluent composition. As the eluent composition increased, the retention time and the front of the response curve became faster and sharper, respectively. By using the modifier in a weak solvent, mixtures of o-/m?cresols and o-/p?cresols were easily separated whereas that of m-/p?cresols was not. The values on the scale of axial eddy dispersion were much larger than those of the gas system. For o?cresol, these values diminished with increasing eluent composition, while for m? and p?cresols the trend was reversed. For all systems, both intraparticle mass transfer and axial dispersion were dominant.     

Study on the Synthesis and Interfacial Interaction Performance of Novel Dodecylamine‐Based Bonding Agents Used for Composite Solid Propellants

An effective pathway was explored to design and select proper bonding agents that could effectively improve the interfacial interactions between bonding agents and solid particles, with three novel synthesized alkyl bonding agents, dodecylamine‐N,N‐di‐2‐hydroxypropyl‐acetate (DIHPA), dodecylamine‐N,N‐di‐2‐hydroxypropyl‐hydroxy‐acetate (DIHPHA) and dodecylamine‐N,N‐di‐2‐hydroxypropyl‐cyano‐acetate (DIHPCA), as examples. Molecular dynamics simulation was applied to compare unit bond energies of these bonding agents with the [110] crystal face of ammonium perchlorate (AP) and the [120] crystal face of hexogen (RDX). The infrared test was used to characterize the interfacial interactions of these bonding agents with AP or RDX. XPS test was applied to calculate the adhesion percentage of the bonding agents on the surface of precoated AP or RDX particles. All of the above results indicated that these three bonding agents have strong interfacial interactions with AP or RDX in the order of DIHPCA>DIHPHA>DIHPA. The prepared three bonding agents were used in HTPB/AP/RDX/Al propellants, and their effects on tensile strength (σ), elongation under maximum tensile strength (ε_m), elongation at breaking point of the propellant (ε_b) and adhesion index (Φ) of the propellant were studied. The results show that the bonding agents improve the mechanical properties of the propellant in the order of DIHPCA>DIHPHA>DIHPA. The methods found from theoretical design, materials synthesis, and mechanistics studies up to practical application show effective guiding significance for choosing the proper bonding agent and improving the interfacial interactions between the solid particles and binder matrix.     

Aromatic rings as cure sites for EPM elastomers

Terpolymers of ethylene and propylene with 4-phenyl-, 4-o-tolyl, 4-p-tolyl, and 4-(1-naphthyl)-1-butenes were vulcanized with bisbenzylic halides in the presence of highly acidic clays. The halides include bischloromethyldurene, p-bischloromethylbenzene, and p-bisbromomethylbenzene. Since the polymers contain no olefinic unsaturation, the crosslinking is achieved by electrophilic attack of the halide on the pendant aromatic rings. The order of activity is naphthyl > tolyl > phenyl. The new curing system also reacts with olefinic unsaturation. Thus, an EPDM elastomer and SBR rubber, the latter containing both aromatic rings and double bonds, were also readily crosslinked.     

Separation of close boiling substituted phenols by dissociation extraction

Some mixtures of substituted phenols, which are difficult to separate by established methods such as distillation, crystallisation, etc., have been separated by dissociation extraction. Di-n-butyl ether was found to be an excellent solvent for the systems: phenol-o-chlorophenol; p-chlorophenol-2,4-dichlorophenol; o-cresol-6-chloro-o-cresol. In the case of m-cresol-2,6-xylenol and p-cresol-2,6-xylenol, benzene was found to be a good solvent. For the system: 4-chloro-m-xylenol-2,4-dichloro-m-xylenol dissociation extraction in a solid-liquid system without a solvent gave higher values of separation factor than a liquid-liquid system. In all the cases, agreement between the experimental and theoretical values of separation factors was found to be reasonable.     

Excess Gibbs free energy of butyl acetate with cyclohexane and aromatic hydrocarbons at 308.15K

Molar excess Gibbs free energies of mixing (C ^E ) for butyl acetate+cyclohexane or benzene or toluene or o- or m- or p-xylene were calculated by using Barker’s method from the measured vapor pressure data by static method at 308.15±0.01 K over the entire composition range. The G ^E values for the binary mixtures containing cyclohexane or benzene are positive; while these are negative for toluene, o-, m- and p-xylene system over the whole composition range. The G ^E values of an equimolar mixture for these systems vary in the order: cyclohexane>benzene>o-xylene>m-xylene>p-xylene>toluene. The G ^E values for these systems were also calculated by Sanchez and Lacome theory using the previously published excess enthalpy and excess volume data. It is found that while values of G ^E from Sanchez and Lacombe theory are in reasonably good agreement with those calculated by Barker method for m-xylene and p-xylene mixtures, agreement is very poor for other systems although they predict the sign of G ^E data except in the case of mixtures containing benzene.     

Theoretical and experimental study on the selectivity of dehydrogenation of α-limonene in ZSM-5 and zeolite-Y

Dehydrogenation of the natural terpene α-limonene to the industrially important p-cymene was studied over two zeolite-supported Pd catalysts, ZSM-5 and zeolite-Y. Reactor tests indicate that transalkylation of the p-cymene product can be avoided by employing the shape-selective properties of a medium-pore ZSM-5 catalyst. The diffusion properties of the three isomers of cymene were then calculated in the two zeolites using molecular mechanics. In case of ZSM-5, p-cymene was found to have the lowest barrier of the three isomers for diffusion through the straight, spherical channel of the zeolite. For zeolite-Y, differences in diffusivity for the three isomers were very small. Theory and experiments showed, in excellent agreement, that only ZSM-5 selectively produces p-cymene. This work shows that molecular mechanics is a powerful and reliable method for the screening of zeolites for performing shape-selective catalysis. This revised version was published online in July 2006 with corrections to the Cover Date.     

Removal of TEX vapours from air in a peat biofilter: influence of inlet concentration and inlet load

This paper presents the results of the study of the removal of toluene, ethylbenzene, and o‐xylene (TEX) by biofiltration using a commercial peat as filter‐bed material. Runs with a single organic compound in air, and with the mixture of TEX in air, were carried out for at least 55 days in laboratory‐scale reactors inoculated with a conditioned culture. The influence of organic compound inlet load and of gas flow rate on the biofilter's performance was studied, including relatively high values of pollutant inlet concentration (up to 4.3 gC m^?3 for ethylbenzene, 3.2 gC m^?3 for toluene, and 2.7 gC m^?3 for o‐xylene). Results obtained show maximum elimination capacities of 65 gC m^?3 h^?1 for o‐xylene, 90 gC m^?3 h^?1 for toluene, and 100 gC m^?3 h^?1 for ethylbenzene, and high removal efficiency (>90%) even for moderately elevated concentrations: 3.0, 2.5 and 1.8 gC m^?3 for ethylbenzene, toluene and o‐xylene, respectively. The behaviour of the TEX mixture was in good agreement with the results obtained for the runs in which only one organic compound was present. Ethylbenzene and toluene are degraded easier than o‐xylene, and inhibitory effects due to the presence of multiple substrates were not observed. Copyright © 2005 Society of Chemical Industry     

Discovery of N-Aryloxypropylbenzylamines as Voltage-Gated Sodium Channel NaV1.2-Subtype-Selective Inhibitors

We previously reported that a lipophilic N-(4′-hydroxy-3′,5′-di-tert-butylbenzyl) derivative ( 1 ) of the voltage-gated sodium channel blocker mexiletine, was a more potent sodium channel blocker in vitro and in vivo. We demonstrate that replacing the chiral methylethylene linker between the amine and di-tert-butylphenol with an achiral 1,3-propylene linker (to give ( 2 )) maintains potency in vitro. We synthesized 25 analogues bearing the 1,3-propylene linker and found that minor structural changes resulted in pronounced changes in state dependence of blocking human Na_V1.2 and 1.6 channels by high-throughput patch-clamp analysis. Compared to mexiletine, compounds 1 and 2 are highly selective Na_V1.2 inhibitors and >500 times less potent in inhibiting Na_V1.6 channels. On the other hand, a derivative (compound 4 ) bearing 2,6-dimethoxy groups in place of the 2,6-dimethyl groups found in mexiletine was found to be the most potent inhibitor, but is nonselective against both channels in the tonic, frequency-dependent and inactivated states. In a kindled mouse model of refractory epilepsy, compound 2 inhibited seizures induced by 6 Hz 44 mA electrical stimulation with an IC₅₀ value of 49.9±1.6 mg kg⁻¹. As established sodium channel blockers do not suppress seizures in this mouse model, this indicates that 2 could be a promising candidate for treating pharmaco-resistant epilepsy.     

Fluorine-containing organic molecules as structure directing agents in the synthesis of crystalline microporous materials. Part III: Synthesis of all-silica zeolites from fluorine-containing derivatives of 1-benzyl-1-methylpyrrolidinium

In order to investigate the effect that a variation of the chemical nature of the structure directing agent may have in the products of synthesis, the cation 1-benzyl-1-methylpyrrolidinium (BMPIRROL) and several fluorinated derivatives of this cation have been employed as structure directing agents in the synthesis of pure silica molecular sieves in fluoride medium. It has been found that the hydrogen-bearing cation strongly directs the formation of pure silica zeolite beta, highly crystalline and stable at long crystallization time. On the contrary, employing the same synthesis conditions and molar compositions, only the 1-orthofluorobenzyl-1-methylpyrrolidinium (o-FBMPIRROL) directs the crystallization of this phase while the 1-metafluorobenzyl-1-methylpyrrolidinium (m-FBMPIRROL) and the 1-parafluorobenzyl-1-methylpyrrolidinium (p-FBMPIRROL) direct the formation of the ZSM-12 zeolite. The fluorinated derivatives are more unstable than their hydrogen-bearing counterpart since the co-crystallization of the small pore octadecasil structure was observed for the three fluorinated derivatives. Nevertheless, the results show that the presence of fluorine in the organic molecule and its position in the aromatic ring has a marked effect in the crystallization pathway.     

Separation of o- and p- chlorotoluene by solvent extraction

Phase equilibrium data are presented for o- and p-chlorotoluene distributed between n-heptane and aq. methanol (95 vol.-%), ‘Sulfolane’ and dimethyl sulphoxide (DMSO) and used to evaluate the possibility of employing distribution between these solvents as a means of separating a mixture of the isomers.     

Isopropylation of ethylbenzene over MCM-22 molecular sieve

MCM-22 materials (Si/Al ratios 24, 50 and 75) were synthesized and characterized. The catalytic activity was examined in the vapour phase isopropylation of ethylbenzene with isopropyl alcohol. Based on ethylbenzene conversion, the order of activity of the catalysts is found to be MCM-22(50) > MCM-22(24) = MCM-22(75). The selective formation of p-isopropyl ethylbenzene (p-IPEB) suggests that the reaction occurs mainly inside the 10-membered ring channel. The time on stream study over MCM-22(50) showed steady conversion for 6 h with nearly the same selectivity to p-isopropyl ethylbenzene (p-IPEB) and o-isopropyl ethylbenzene (p-IPEB).     

Alkylation of toluene with ethene over H-ZSM-5 zeolites

It is shown that the alkylation of toluene with ethylene to give p-ethyltoluene can be conducted selectively on small crystals ( 1μ) of unmodified H-ZSM-5 zeolites to a level higher than that corresponding to a thermodynamic equilibrium composition. A comparison of the ethyltoluene isomers formed with H-Y and H-ZSM-5 zeolites at various conversions and temperatures indicates that p-ethyltoluene is preferentially formed in the channel intersections of the H-ZSM-5 zeolite, even during the initial alkylation step. The final ethyltoluene isomer composition is a result of competition between the rates of alkylation and isomerization and subsequent diffusional transport of individual isomers through the zeolite channels. Zeolite coking causes an apparent increase in the p-ethyltoluene selectivity; however, a more dramatic decrease in toluene conversion results in the formation of a considerably lower amount of p-ethyltoluene. This is caused by a partial blocking of the zeolite channel system.