Anodic Oxidation of α‐Lipoic Acid at a Glassy Carbon Electrode and Its Determination in Dietary Supplements

Abstract

Direct electrochemistry of alpha‐lipoic acid (ALA) was performed at a glassy carbon electrode using cyclic, differential pulse and square wave voltammetry over a wide range of pH. The oxidation of ALA is an irreversible process, pH independent, and involves the charge transfer of one electron. The diffusion coefficient of ALA was calculated from the results obtained at pH 6.9 in 0.1 M phosphate buffer and was shown to be D ₀=1.1×10^?5 cm² s^?1. The limits of detection (LOD) and quantification (LOQ) calculated from the results obtained at this pH are 1.8 and 6.1 µM, respectively.

The lipoic acid content in two dietary supplements samples, a syrup containing ALA and capsules of ALA, has been determined directly at the glassy carbon electrode by differential pulse voltammetry using the standard addition method.     

Kinetics of the reactions of OH with 3‐methyl‐2‐cyclohexen‐1‐one and 3,5,5‐trimethyl‐2‐cyclohexen‐1‐one under simulated atmospheric conditions

Relative rate coefficients for the reactions of OH with 3‐methyl‐2‐cyclohexen‐1‐one and 3,5,5‐trimethyl‐2‐cyclohexen‐1‐one have been determined at 298 K and atmospheric pressure by the relative rate technique. OH radicals were generated by the photolysis of methyl nitrite in synthetic air mixtures containing ppm levels of nitric oxide together with the test and reference substrates. The concentrations of the test and reference substrates were followed by gas chromatography. Based on the value k(OH + cyclohexene) = (6.77 ± 1.35) × 10^?11 cm³ molecule^?1 s^?1, rate coefficients for k(OH + 3‐methyl‐2‐cyclohexen‐1‐one) = (3.1 ± 1.0) × 10^?11 and k(OH + 3,5,5‐trimethyl‐2‐cyclohexen‐1‐one) = (2.4 ± 0.7) × 10^?11 cm³ molecule^?1 s^?1 were determined. To test the system we also measured k(OH + isoprene) = (1.11 ± 0.23) × 10^?10 cm³ molecule^?1 s^?1, relative to the value k(OH + (E)‐2‐butene) = (6.4 ± 1.28) × 10^?11 cm³ molecule^?1 s^?1. The results are discussed in terms of structure–activity relationships, and the reactivities of cyclic ketones formed in the photo‐oxidation of monoterpene are estimated. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 7–11, 2002     

Electrochemical Properties of Th(IV)‐Hexacyanoferrate Sol‐Gel Carbon Composite Electrode: Electrocatalytic Oxidation of Dopamine and Ascorbic Acid

A new sol‐gel carbon composite electrode using hexacyanoferrate (HCF)‐Th(IV) ion pair as a suitable modifier is fabricated in the present study. The Th(IV)‐HCF‐sol‐gel carbon composite electrode (THCF‐CCE) has been prepared by mixing methyl trimethoxysilan (MTMOS) sol‐gel precursor and carbon powder with ion pair and then to fix in a plastic tube. Cyclic voltammetry and chronoamperometry were employed to study the electrochemical and electrocatalytic properties of proposed electrode. The apparent charge transfer rate constant, k_s, and transfer coefficient, α, for electron transfer between ion‐pair and sol‐gel CPE were calculated as 3.10 ± 0.10 s^?1 and 0.52, respectively. The THCF‐CCE showed a significant electrocatalytic activity towards oxidation of ascorbic acid (AA) and dopamine (DA) in 0.1 M acidic phosphate buffer solutions (pH 3) containing KCl as a supporting electrolyte. The mean value of the diffusion coefficients for ascorbic acid and dopamine were found 4.12 × 10^?5 and 4.43 × 10^?5 (cm²s^?1), respectively. High stability, good reproducibility, rapid response, easy surface regeneration and fabrication are the important characteristics of the proposed sensor. The resulting peaks from the electrocatalytic oxidation of AA and DA were well resolved with good sensitivity. A linear response was observed for AA and DA in the concentration range of 1 × 10^?5 to 3 × 10^?3 M and 4 × 10^?6 to 2.2 × 10^?4 M, respectively.     

Measurements of the kinetics of the OH‐initiated oxidation of methyl vinyl ketone and methacrolein

The mechanisms of the OH‐initiated oxidation of methyl vinyl ketone and methacrolein have been studied at 300 K and 100 Torr total pressure, using a turbulent flow technique coupled with laser‐induced fluorescence detection of the OH radical. The rate constants for the OH + methyl vinyl ketone and OH + methacrolein reactions were measured to be (1.78 ± 0.08) × 10^?11 and (3.22 ± 0.10) × 10^?11 cm³ molecule^?1 s^?1, respectively, and were found to be in excellent agreement with previous studies. In the presence of O₂ and NO, the OH radical propagation and the loss of OH through radical termination resulting from the production of methyl vinyl ketone‐ and methacrolein‐based alkyl nitrates were measured at 100 Torr total pressure and compared to the simulations of the kinetics of these reaction systems. The results of these experiments are consistent with an overall rate constant of (2.0 ± 1.3) × 10^?11 cm³ molecule^?1 s^?1 for both the methyl vinyl ketone‐based peroxy radical + NO and methacrolein‐based peroxy radical + NO reactions, each with branching ratios of 0.90 ± 0.10 for the bimolecular channel (oxidation of NO to NO₂) and 0.10 ± 0.10 for the termolecular channel (production of methyl vinyl ketone‐ and methacrolein‐based alkyl nitrates). © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 12–25, 2003     

Electrocatalytic Determination of Ascorbic Acid at the Surface of 2,7‐Bis(ferrocenyl ethyl)fluoren‐9‐one Modified Carbon Paste Electrode

A chemically modified carbon paste electrode with 2,7‐bis(ferrocenyl ethyl)fluoren‐9‐one (2,7‐BFEFMCPE) was employed to study the electrocatalytic oxidation of ascorbic acid in aqueous solution using cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The diffusion coefficient (D=1.89×10^?5 cm² s^?1), and the kinetic parameter such as the electron transfer coefficient, α (=0.42) of ascorbic acid oxidation at the surface of 2,7‐BFEFMCPE was determined using electrochemical approaches. It has been found that under an optimum condition (pH 7.00), the oxidation of ascorbic acid at the surface of such an electrode occurs at a potential about 300 mV less positive than that of an unmodified carbon paste electrode. The catalytic oxidation peak currents show a linear dependence on the ascorbic acid concentration and linear analytical curves were obtained in the ranges of 8.0×10^?5 M–2.0×10^?3 M and 3.1×10^?5 M–3.3×10^?3 M of ascorbic acid with correlation coefficients of 0.9980 and 0.9976 in cyclic voltammetry and differential pulse voltammetry, respectively. The detection limits (2δ) were determined to be 2.9×10^?5 M and 9.0×10^?6 M with cyclic voltammetry and differential pulse voltammetry, respectively. This method was also examined for determination of ascorbic acid in pharmaceutical preparations.     

Gas‐phase ozonolysis: Rate coefficients for a series of terpenes and rate coefficients and OH yields for 2‐methyl‐2‐butene and 2,3‐dimethyl‐2‐butene

The kinetics of the gas‐phase reactions of O₃ with a series of selected terpenes has been investigated under flow‐tube conditions at a pressure of 100 mbar synthetic air at 295 ± 0.5 K. In the presence of a large excess of m‐xylene as an OH radical scavenger, rate coefficients k(O₃+terpene) were obtained with a relative rate technique, (unit: cm³ molecule^?1 s^?1, errors represent 2σ): α‐pinene: (1.1 ± 0.2) × 10^?16, ³Δ‐carene: (5.9 ± 1.0) × 10^?17, limonene: (2.5 ± 0.3) × 10^?16, myrcene: (4.8 ± 0.6) × 10^?16, trans‐ocimene: (5.5 ± 0.8) × 10^?16, terpinolene: (1.6 ± 0.4) × 10^?15 and α‐terpinene: (1.5 ± 0.4) × 10^?14. Absolute rate coefficients for the reaction of O₃ with the used reference substances (2‐methyl‐2‐butene and 2,3‐dimethyl‐2‐butene) were measured in a stopped‐flow system at a pressure of 500 mbar synthetic air at 295 ± 2 K using FT‐IR spectroscopy, (unit: cm³ molecule^?1 s^?1, errors represent 2σ ): 2‐methyl‐2‐butene: (4.1 ± 0.5) × 10^?16 and 2,3‐dimethyl‐2‐butene: (1.0 ± 0.2) × 10^?15. In addition, OH radical yields were found to be 0.47 ± 0.04 for 2‐methyl‐2‐butene and 0.77 ± 0.04 for 2,3‐dimethyl‐2‐butene. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 394–403, 2002     

A Solid State Polymer‐Coated Electrode Containing a Chiral Crown Ether Derivative for Enantioselective Detection of Phenylglycine Methyl Ester Isomer

All solid‐state enantioselective electrode (ASESE) based on a newly synthesized chiral crown ether derivative ((R)‐(?)‐(3,3′‐diphenyl‐1,1′‐binaphthyl)‐23‐crown‐6 incorporating 1,4‐dimethoxybenzene) was prepared and characterized by potentiometry. The ASESE clearly showed enantiomer discrimination for methyl esters of alanine, leucine, valine, phenylalanine, and phenylglycine, where the enantioselectivity for phenylglycine methyl ester was the highest (K_R,S=8.5±7.1%). Experimental parameters of ASESE for the analysis of (R)‐(?)‐phenylglycine methyl ester were optimized. The optimized ASESE showed a slope of 55.3±0.2 mV/dec for (R)‐(?)‐phenylglycine methyl ester in the concentration range of 1.0×10^?5–1.0×10^?2 M and the detection limit was 9.0×10^?6 M. The ASESE showed good selectivity for (R)‐(?)‐phenylglycine methyl ester against inorganic cations and various amino acid methyl esters. The concentration of (R)‐(?)‐phenylglycine methyl ester was determined in the mixture of (R)‐(?) and (S)‐(+)‐phenylglycine methyl ester, which ratios varied from 2 : 1 to 1 : 9. The lifespan of the electrode was alleged to be 30 days.     

Rate constants for the gas‐phase reactions of Cl atoms with a series of ethers

The laser photolysis–resonance fluorescence technique has been used to determine the absolute rate coefficient for the Cl atom reaction with a series of ethers, at room temperature (298 ± 2) K and in the pressure range 15–60 Torr. The rate coefficients obtained (in units of cm³ molecule⁻¹ s⁻¹) are dimethyl ether (1.3 ± 0.2) × 10⁻¹⁰, diethyl ether (2.5 ± 0.3) × 10⁻¹⁰, di‐n‐propyl ether (3.6 ± 0.4) × 10⁻¹⁰, di‐n‐butyl ether (4.5 ± 0.5) × 10⁻¹⁰, di‐isopropyl ether (1.6 ± 0.2) × 10⁻¹⁰, methyl tert‐butyl ether (1.4 ± 0.2) × 10⁻¹⁰, and ethyl tert‐butyl ether (1.5 ± 0.2) × 10⁻¹⁰. The results are discussed in terms of structure–reactivity relationship. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 105–110, 2000     

Electroanalytical Performance of (SiPy+Cl−/CuTsPc)5 LbL Film for Detecting Promethazine Hydrochloride

A (SiPy⁺Cl^?/CuTsPc)₅ layer‐by‐layer film was employed for the electroanalytical determination of promethazine hydrochloride in BR buffer pH 5.0 with peaks at 0.48 and 0.79 V. After optimisation of the square‐wave parameters (f=100 s^?1, a=40 mV and ΔE_s=2 mV), the peak at 0.79 V was used for quantification and a detection limit of 8.71×10^?9 mol L^?1 and a quantification limit of 9.31×10^?8 were calculated. The applicability of this procedure was tested on commercial formulations of promethazine hydrochloride by observing the stability, specificity, recovery and precision of the procedure in complex samples, without any preliminary treatment.     

Studies on reaction of reduced lipoic acid with Mukaiyama reagent and its application for pharmaceutical and food analysis

A new sensitive method for the determination of lipoic acid (LA) in selected food items based on its reaction with Mukaiyama reagent (2-chloro-1-methylpyridinium iodide, CMPI) was developed. It was stated that CMPI reacts with reduced form of lipoic acid (dihydrolipoic acid, DHLA) and the stable product is produced. The spectrum of the labeled form of DHLA exhibits new band at 312?nm. Based on its spectral characteristics new spectrophotometric and UV–high-performance liquid chromatography (HPLC) methods of LA determination were elaborated. Both methods allowed determination of the analyte in the concentration range of 5?×?10^?6–1?×?10^?4?mol?L^?1 with limit of detection 0.39?×?10^?6 and 0.77?×?10^?6?mol?L^?1 for spectrophotometric and HPLC method, respectively. The practical usability of newly developed methods was checked by determination of lipoic acid contents in its pharmaceutical preparate Revitanerw. The proposed method was precise and accurate. The relative error of determination did not exceed ±0.067%. As chromatographic method allowed the determination of analyte in the presence of complex matrix, it was applied for assay of free fraction of α-lipoic acid in selected food items. A procedure of LA isolation from biological matrix was developed. The extraction with dichloromethane allowed quantitative recovery at 102.94?±?4.20%. The green barley appeared to be the richest source of LA.     

Development and validation of a LC‐MS assay for the quantification of ikh12 a novel anti‐tumor candidate in rat plasma and tissues and its application in a pharmacokinetic study

IKH12 is a novel histone deacetylase 6 selective inhibitor. A rapid and sensitive liquid chromatography tandem mass spectrometry method was developed and validated for the quantification of IKH12 in rat plasma and tissue with kendine 91 as internal standard (IS). The samples were prepared by liquid–liquid extraction with tert‐butyl methyl ether. The chromatographic separation was accomplished by using a Zorbax Extend C₁₈ 4.6 × 150 mm, 5 µm column, with a mobile phase consisting of methanol and 0.1% formic acid (75:25 v/v). Multiple reaction monitoring, using electrospray ionization in positive ion mode, was employed to quantitatively detect IKH12 and IS. The monitored transitions were set at m/z 418 → 252 and 444 → 169 for IKH12 and kendine 91, respectively. The calibration curve was linear over the concentration range 2–1000 ng mL^?1. The intra‐ and inter‐assay precision and accuracy of the quality controls and the limit of quantification were satisfactory in all cases (according to European Medicines Agency guidelines). Stability studies showed that plasma samples were stable in the chromatography rack for 24 h and at ?80 °C for 2 months and also after three freeze–thaw cycles. This method was successfully applied to a pharmacokinetic study of IKH12 in rat. Copyright © 2015 John Wiley & Sons, Ltd.     

Kinetics and mechanism of the atmospheric oxidation of tertiary amyl methyl ether

Tertiary-amyl methyl ether (TAME) is proposed for use as an additive to increase the oxygen content of gasoline as stipulated in the 1990 Clean Air Amendments. The present experiments have been performed to examine the kinetics and mechanisms of the atmospheric removal of TAME. The kinetics of the reaction of OH with TAME was examined by using a relative rate technique in which photolysis of methyl nitrite or nitrous acid was used as the source of OH. The OH rate constant for TAME and two major products (t-amyl formate and methyl acetate) were measured and yields for ten products were determined as primary products from the reaction. Values determined for the rate constants for the reaction with OH were 5.48 × 10^?12 (TAME), 1.75 × 10^?12 (t-amyl formate), and 3.85 × 10^?13 cm³ molec^?1 s^?1 (methyl acetate) at 298 ± 2 K. The primary products (with corrected yields where required) from the OH + TAME that have been observed include (1) t-amyl formate (0.366), methyl acetate (0.349), acetaldehyde (0.43, corrected), acetone (0.036), formaldehyde (0.549), t-amyl alcohol (0.026), 3-methyoxy-3-methyl-butanal (0.044, corrected), t-amyloxy methyl nitrate (0.029), 3-methyoxy-3-methyl-2-butyl nitrate (0.010), and 2-methoxy-2-methyl butyl nitrate (0.004). Mechanisms leading to these products involve OH abstraction from each of the four different hydrogen atoms of TAME. © 1995 John Wiley & Sons, Inc.     

Arrhenius parameters for the gas‐phase reactions of O3 with two butenes and two methyl‐substituted butenes over the temperature range of 295–351 K

Gas‐phase reactions of ozone with two butenes (1‐butene and isobutene) and two methyl‐substituted butenes (2‐methyl‐1‐butene and 3‐methyl‐1‐butene) have been studied in an indoor chamber at 295–351 K. The O₃ concentrations were monitored by Model 49C‐Ozone analyzer. The butene concentrations were measured by gas chromatography–flame ionization detector. The Arrhenius expressions of k=3.50×10^?15e^{(?1756±84)/T} cm³ molecule^?1 s^?1, k=3.39×10^?15e^{(?1697±52)/T} cm³ molecule^?1 s^?1, k=6.18×10^?15e^{?(1822±80)/T} cm³ molecule^?1 s^?1, and k=7.24×10^?14e^{?(2741±139)/T} cm³ molecule^?1 s^?1 were obtained for the ozonolysis reactions of 1‐butene, isobutene, 2‐methyl‐1‐butene, and 3‐methyl‐1‐butene, respectively. Both the reaction rate constant and activation energy obtained in this work are in good agreement with those reported by using different techniques in the literature. © 2011 Wiley Peiodicals, Inc. Int J Chem Kinet 43: 238–246, 2011     

Preparation and properties of macroporous superabsorbent composite

A fast swelling macroporous superabsorbent composite was prepared by the copolymerization of partially neutralized acrylic acid, 2‐acryloylamino‐2‐methyl‐1‐propanesulfonic acid (AMPS), and attapulgite (APT) using N, N′‐methylenebisacrylamide (NNMBA) and trihydroxymethyl propane glycidol ether as crosslinking agents. For fast swelling rate (SR), sodium bicarbonate, polyethylene glycol (PEG), and sodium carboxymethylcellulose (CMC) were introduced into the reaction system as foaming agent and stabilizers. Furthermore, the copolymer was surface‐crosslinked with glycerine and sodium silicate, and then blended with aluminum sulfate and sodium carbonate. The influences of the amount of NNMBA, trihydroxymethyl propane glycidol ether, PEG, CMC and sodium bicarbonate, and reaction temperature on water absorbence both under atmospheric pressure and load, and on the SR were investigated. The water absorbence of the sample in 0.9 wt% NaCl aqueous solution under atmospheric pressure and certain load (P ≈ 2 × 10³ Pa) could reach 54 and 8 g.g^?1, respectively, and the SR could reach 0.471 ml g^?1 s^?1. The excellent strength, resilience, and the dispersion of swollen hydrogel were also observed for the sample. Moreover, the surface morphology of macroporous superabsorbent composite was characterized using scanning electron microscope. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation and characterization of branched and linear sulfonated poly(ether ketone sulfone) proton exchange membranes for fuel cell applications

Branched sulfonated poly(ether ketone sulfone)s (Br‐SPEKS) were prepared with bisphenol A, bis(4‐fluorophenyl)sulfone, 3,3′‐disodiumsulfonyl‐4,4′‐difluorobenzophenone, and THPE (1,1,1‐tris‐p‐hydroxyphenylethane), respectively, at 180 °C using potassium carbonate in NMP (N‐methylpyrrolidinone). THPE, as a branching agent, was used with 0.4 mol % of bisphenol A to synthesize branched copolymers. Copolymers containing 10–50 mol % disulfonated units were cast from dimethylsulfoxide solutions to form films. Linear sulfonated poly(ether ketone sulfone)s (SPEKS) were also synthesized without THPE. The films were converted from the salt to acid forms with dilute hydrochloric acid. A series of copolymers were studied by Fourier transform infrared, ¹H‐NMR spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. The ion‐exchange capacity (IEC), a measure of proton conductivity, was evaluated. The synthesized Br‐SPEKS and SPEKS membranes exhibit conductivities (25 °C) from 1.04 × 10^?3 to 4.32 × 10^?3 S/cm, water swell from 20.18 to 62.35%, IEC from 0.24 to 0.83 mequiv/g, and methanol diffusion coefficients from 3.2 × 10^?7 to 4.7 × 10^?7 cm²/S at 25 °C. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1792–1799, 2008     

Hybrid phospholipid bilayer coatings for separations of cationic proteins in capillary zone electrophoresis

Protein separations in CZE suffer from nonspecific adsorption of analytes to the capillary surface. Semipermanent phospholipid bilayers have been used to minimize adsorption, but must be regenerated regularly to ensure reproducibility. We investigated the formation, characterization, and use of hybrid phospholipid bilayers (HPBs) as more stable biosurfactant capillary coatings for CZE protein separations. HPBs are formed by covalently modifying a support with a hydrophobic monolayer onto which a self‐assembled lipid monolayer is deposited. Monolayers prepared in capillaries using 3‐cyanopropyldimethylchlorosilane (CPDCS) or n‐octyldimethylchlorosilane (ODCS) yielded hydrophobic surfaces with lowered surface free energies of 6.0 ± 0.3 or 0.2 ± 0.1 mJ m^?2, respectively, compared to 17 ± 1 mJ m^?2 for bare silica capillaries. HPBs were formed by subsequently fusing vesicles comprised of 1,2‐dilauroyl‐sn‐glycero‐3‐phosphocholine or 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine to CPDCS‐ or ODCS‐modified capillaries. The resultant HPB coatings shielded the capillary surface and yielded reduced electroosmotic mobility (1.3–1.9 × 10^?4 cm² V^?1s^?1) compared to CPDCS‐ and ODCS‐modified or bare capillaries (3.6 ± 0.2 × 10^?4 cm² V^?1s^?1, 4.8 ± 0.4 × 10^?4 cm² V^?1s^?1, and 6.0 ± 0.2 × 10^?4 cm² V^?1s^?1, respectively), with increased stability compared to phospholipid bilayer coatings. HPB‐coated capillaries yielded reproducible protein migration times (RSD ≤ 3.6%, n ≥ 6) with separation efficiencies as high as 200 000 plates/m.     

Rate coefficients for the gas‐phase reactions of OH radicals with methylbutenols at 298 K

The relative‐rate method has been used to determine the rate coefficients for the reactions of OH radicals with three C₅ biogenic alcohols, 2‐methyl‐3‐buten‐2‐ol (k₁), 3‐methyl‐3‐buten‐1‐ol (k₂), and 3‐methyl‐2‐buten‐1‐ol (k₃), in the gas phase. OH radicals were produced by the photolysis of CH₃ONO in the presence of NO. Di‐n‐butyl ether and propene were used as the reference compounds. The absolute rate coefficients obtained with the two reference compounds agreed well with each other. The O₃ and O‐atom reactions with the target alcohols were confirmed to have a negligible contribution to their total losses by using two kinds of light sources with different relative rates of CH₃ONO and NO₂ photolysis. The absolute rate coefficients were obtained as the weighted mean values for the two reference compound systems and were k₁ = (6.6 ± 0.5) × 10^?11, k₂ = (9.7 ± 0.7) × 10^?11, and k₃ = (1.5 ± 0.1) × 10^?10 cm³ molecule^?1 s^?1 at 298 ± 2 K and 760 torr of air. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 379–385 2004     

Synthesis and proton conductivities of phosphonic acid containing poly‐(arylene ether)s

A novel phosphonic acid containing bisphenol was successfully synthesized from phenolphthalein and m‐aminophenylphosphonic acid. A series of homo‐ and copoly‐(arylene ether)s containing phosphonic acid groups were prepared by solution nucleophilic polycondensation. These phosphonic acid containing polymers can readily be dissolved in common organic solvents, such as dimethyl sulfoxide, N‐methyl‐2‐pyrrolidinone, and N‐cyclohexylpyrrolidinone, and can be cast into tough and smooth films. The presence of phosphonic acid pendants in the poly‐(arylene ether)s was confirmed by NMR, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, and conductivity measurements. This is the first report on the attachment of phenylphosphonic acid groups as side chains to aromatic polyethers. These poly‐(arylene ether)s had very high glass‐transition temperatures ranging from 254 to >315 °C and high molecular weights. The conductivities of the synthesized polymers were analyzed by the Cole–Cole method, and they ranged from 10^?5 to 10^?6 Scm^?1. The synthesized polymers also exhibited good solution processability. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3218–3226, 2001     

Kinetics and mechanism of the reaction of propylene oxide with chlorine atoms and hydroxy radicals

The kinetics and mechanism of gas‐phase propylene oxide (PPO) reactions were studied in a 142‐L reaction chamber by long‐path Fourier transform infrared spectroscopy at atmospheric pressure and 298 K. Rate coefficients for the reaction of PPO with ozone (O₃), chlorine atoms (Cl), and hydroxyl radicals (OH) were measured using the relative rate technique. Product yields of acetic acid, acetic formic anhydride, formic acid, and carbon monoxide were determined for the following reactions: PPO with Cl both in the presence and absence of NO, PPO with OH and NO, methyl acetate with Cl both in the presence and absence of NO, and ethyl formate with Cl both in the presence and absence of NO. The measured rate coefficients for PPO with O₃, Cl, and OH are <3.5 × 10^?21 cm³ molecule^?1 s^?1, (3.0 ± 0.7) × 10^?11 cm³ molecule^?1 s^?1, and (3.0 ± 1.0) × 10^?13 cm³ molecule^?1 s^?1, respectively. The carbon balance for the products measured ranged from 10% (for OH + PPO) to 100% (for Cl + methyl acetate in the absence of NO). The mechanistic and atmospheric implications of these measurements are discussed. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 507–521, 2011     

Synthesis of 1‐Methyl‐3‐aryl‐substituted Titanocene and Zirconocene Dichlorides and Crystal Structure of Bis[η5‐1‐methyl‐3‐(α, α‐dimethylbenzyl) cyclopentadienyl] titanium Dichloride

The syntheses of a series of l‐methyl‐3‐aryl‐substituted titanocene and zirconocene dichlorides are reported. These complexes are synthesized by the reaction of 2‐ and 3‐methyl‐6, 6‐dimethylfulvenes (1:4) with aryllithium, followed by the reaction with TiCl₄·2THF, ZrCl₄ and (CpTiCl₂)₂O respectively, to give complexes 1–5. The complex [η⁵‐1‐methyl‐3‐(α, α‐dimethylbenzyl) cyclopentadienyl] titanium dichloride has been studied by X‐ray diffraction. The red crystal of this complex is monoclinic, space group P2_t/C with unit cell parameters: a =6.973(6) × 10^?1 nm, b =36.91(2) × 10^?1 nm, c = 10.063(4) × 10^?1 nm, α=β= γ = 93.35(5)°, V = 2584(5) × 10^?3 nm³ and Z = 4. Refinement for 1004 observed reflections gives the final R of 0.088. There are four independent molecules per unit cell.