C2 H5 Research Articles

Interventions for treatment and/or prevention of alcohol hangover: Systematic review.

To evaluate new research conducted over the past few years (2009-2016) assessing the effectiveness of potentially curative and/or preventive methods of alcohol hangover. Data were retrieved by a 4-stage systematic search process. A search of the online Pubmed and Scopus databases were performed, using a combination of keywords: "Alcohol," "Ethanol," and "C2 H5 OH," in combination with the terms "Hangover," "Treatment," and "Prevention." The search comprised studies listed between January 1, 2009 and June 30, 2016. Findings were synthesized using a systematic approach. Quantitative analysis was not done because of the heterogeneity of the included studies. Six controlled human studies were identified (placebo controlled-3, controlled studies with a comparator intervention-3). Of the interventions, the use of polysaccharide rich extract of Acanthopanax senticosus, red ginseng antihangover drink, Korean pear juice, KSS formula, and the After-Effect© were associated with a significant improvement of hangover symptoms (p<.05). The highest improvement was observed for the following symptoms: tiredness, nausea/vomiting, and stomachache. None of the methods were effective for all the symptoms. The available evidence suggests that several products are capable of significantly improving some, but not all, of the symptoms related to alcohol hangover. Therefore, further research is necessary to develop clinically effective hangover treatments.

Gas-phase fragmentations of N-methylimidazolidin-4-one organocatalysts.

N-methylimidazolidin-4-one organocatalysts were studied in the gas phase. Protonated and sodium-cationized (sodiated) molecules are conveniently accessible by electrospray mass spectrometry. Protonation enables three different closed-shell paths of ring cleavage leading to iminium ions. The fragmentation pattern is largely unaffected by exocyclic substituents and thus is valuable to characterize the substance type as N-methylimidazolidin-4-ones. Sodiated species show a distinctly different fragmentation that is less useful for characterization purposes: apart from signal loss due to dissociation of Na+ , the observation of benzyl radical loss is by far predominant. Only in absence of a benzyl substituent, an analogue of the third ring cleavage (loss of [C2 H5 NO]) is observed. Copyright © 2017 John Wiley & Sons, Ltd.

Near-Ultraviolet Fluorescent "ON-OFF-ON" Switching Sensors Based on Nitrogen-Enriched Dual-Color Single-Functional Polymer Carbon Nanosheets.

Graphene quantum-dot-like structures of highly enriched N-based dual-color single-functional polymer carbon nanosheets (GLNPCNs) with an average diameter as large as 170 nm (ca. five layers) are prepared through a facile hydrothermal method. Intermolecular C5 H5 N5 ⋅⋅⋅C5 H5 N5 and/or C2 H5 OH chemical polymerization interactions in the liquid state of the peripheral crown-ether-like "hole"-decorated compound GLNPCNs lead to a fascinating 2 D supramolecular polymer architecture, which exhibits near-ultraviolet (NUV) fluorescence, ultrahigh brightness, a narrow full-width at half-maximum, and excellent potential for practical applications. The unique NUV fluorescence of the GLNPCNs might be attributed to the "self-passivated" crown-ether-like layer on their surface; the GLNPCNs exhibit properties independent of the excitation wavelength, which is unexpected in the NUV region. Moreover, these GLNPCNs show highly selective and sensitive detection of hazardous and toxic silver (Ag+ ) ions, and discriminate other metal ions or anions in the range 1.5 nm to 50 μm through a fluorescence quenching response. The high sensing selectivity toward Ag+ ions could be attributable to the restricted rigid conformation of the peripheral crown-ether-like "hole", which binds exclusively to the Ag+ ion. In addition to Ag+ ion sensing, the GLNPCNs quenched by Ag+ ions exhibit high selectivity and sensitivity for cysteine (Cys) in the range 2.0 nm to 50 μm through a fluorescence recovery process, which could be attributed to the effective coordination/chelation interactions between Ag+ ions and the plentiful mercapto and amino groups of Cys. Our results suggest that the facile preparation, biocompatibility, outstanding photoluminescence, and physicochemical properties of these GLNPCNs make them potentially useful in numerous applications such as bioimaging, optical and electrochemical sensors, and energy devices.

Atmospheric pressure chemical ionization of explosives induced by soft X-radiation in ion mobility spectrometry: mass spectrometric investigation of the ionization reactions of drift gasses, dopants and alkyl nitrates.

A promising replacement for the radioactive sources commonly encountered in ion mobility spectrometers is a miniaturized, energy-efficient photoionization source that produce the reactant ions via soft X-radiation (2.8 keV). In order to successfully apply the photoionization source, it is imperative to know the spectrum of reactant ions and the subsequent ionization reactions leading to the detection of analytes. To that end, an ionization chamber based on the photoionization source that reproduces the ionization processes in the ion mobility spectrometer and facilitates efficient transfer of the product ions into a mass spectrometer was developed. Photoionization of pure gasses and gas mixtures containing air, N2 , CO2 and N2 O and the dopant CH2 Cl2 is discussed. The main product ions of photoionization are identified and compared with the spectrum of reactant ions formed by radioactive and corona discharge sources on the basis of literature data. The results suggest that photoionization by soft X-radiation in the negative mode is more selective than the other sources. In air, adduct ions of O2- with H2 O and CO2 were exclusively detected. Traces of CO2 impact the formation of adduct ions of O2- and Cl- (upon addition of dopant) and are capable of suppressing them almost completely at high CO2 concentrations. Additionally, the ionization products of four alkyl nitrates (ethylene glycol dinitrate, nitroglycerin, erythritol tetranitrate and pentaerythritol tetranitrate) formed by atmospheric pressure chemical ionization induced by X-ray photoionization in different gasses (air, N2 and N2 O) and dopants (CH2 Cl2 , C2 H5 Br and CH3 I) are investigated. The experimental studies are complemented by density functional theory calculations of the most important adduct ions of the alkyl nitrates (M) used for their spectrometric identification. In addition to the adduct ions [M + NO3 ]- and [M + Cl]- , adduct ions such as [M + N2 O2 ]- , [M + Br]- and [M + I]- were detected, and their gas-phase structures and energetics are investigated by density functional theory calculations. Copyright © 2016 John Wiley & Sons, Ltd.

A Gross-Margin Model for Defining Technoeconomic Benchmarks in the Electroreduction of CO2.

We introduce a gross-margin model to evaluate the technoeconomic feasibility of producing different C1 -C2 chemicals such as carbon monoxide, formic acid, methanol, methane, ethanol, and ethylene through the electroreduction of CO2 . Key performance benchmarks including the maximum operating cell potential (Vmax ), minimum operating current density (jmin ), Faradaic efficiency (FE), and catalyst durability (tcatdur ) are derived. The Vmax values obtained for the different chemicals indicate that CO and HCOOH are the most economically viable products. Selectivity requirements suggest that the coproduction of an economically less feasible chemical (CH3 OH, CH4 , C2 H5 OH, C2 H4 ) with a more feasible chemical (CO, HCOOH) can be a strategy to offset the Vmax requirements for individual products. Other performance requirements such as jmin and tcatdur are also derived, and the feasibility of alternative process designs and operating conditions are evaluated.

Cadmium(II)-Triazole Framework as a Luminescent Probe for Ca(2+) and Cyano Complexes.

A bidentate ligand, 1-{4-[4-(1H-1,2,4-triazol-1-yl)phenoxy]phenyl}-1H-1,2,4-triazole (TPPT), has been designed and synthesized. By using TPPT as a building block for self-assembly with Cd(NO3 )2 ⋅4 H2 O and CdCl2 ⋅10.5 H2 O, novel 1D double-chain {[Cd(TPPT)(NO3 )2 ]⋅3 H2 O}n (1) and 2D (4,4) layer [Cd(TPPT)Cl2 (H2 O)]n (2) have been constructed. When 1 was employed as a precursor and exposed to DMF or N,N'-dimethylacetamide (DMAC), the crystals of 1 dissolved and reassembled into two types of brown block-shaped crystals of 1D double chains: {[Cd(TPPT)2 (NO3 )2 ]⋅DMF}n (1 a) and {[Cd(TPPT)2 (NO3 )2 ]⋅DMAC}n (1 b). The anion-exchange reactions of complex 2 have also been investigated. After gently stirring crystals of 2 in CHCl3 /C2 H5 OH/H2 O containing NaBr, NaI⋅2 H2 O, or NaOAc⋅3 H2 O, the crystals retained their crystalline appearances. A remarkable single crystal to single crystal transformation was observed and 1D double chains of {[Cd(TPPT)Br2 ]⋅C2 H5 OH}n (2 a) and {[Cd(TPPT)2 I2 ]⋅CHCl3 }n (2 b), and 1D single chains of [Cd(TPPT)(H2 O)2 (CH3 COO)2 ]n (2 c), can be obtained. Luminescent properties indicate that 1 shows excellent selectivity for Ca(2+) and cyano complexes. To the best of our knowledge, this is the first example of a luminescent probe for Ca(2+) based on triazole derivatives.

Monolayer Co3 O4 Inverse Opals as Multifunctional Sensors for Volatile Organic Compounds.

Monolayers of periodic porous Co3 O4 inverse opal (IO) thin films for gas-sensor applications were prepared by transferring cobalt-solution-dipped polystyrene (PS) monolayers onto sensor substrates and subsequent removal of the PS template by heat treatment. Monolayer Co3 O4 IO thin films having periodic pores (d≈500 nm) showed a high response of 112.9 to 5 ppm C2 H5 OH at 200 °C with low cross-responses to other interfering gases. Moreover, the selective detection of xylene and methyl benzenes (xylene+toluene) could be achieved simply by tuning the sensor temperature to 250 and 275 °C, respectively, so that multiple gases can be detected with a single chemiresistor. Unprecedentedly high ethanol response and temperature-modulated control of selectivity with respect to ethanol, xylene, and methyl benzenes were attributed to the highly chemiresistive IO nanoarchitecture and to the tuned catalytic promotion of different gas-sensing reactions, respectively. These well-ordered porous nanostructures could have potential in the field of high-performance gas sensors based on p-type oxide semiconductors.

Switchable Room-Temperature Ferroelectric Behavior, Selective Sorption and Solvent-Exchange Studies of [H3 O][Co2 (dat)(sdba)2 ]⋅H2 sdba⋅5 H2 O.

A newly synthesized compound, [H3 O][Co2 (dat)(sdba)2 ]⋅H2 sdba⋅5 H2 O (I, dat=3,5-diamino-1,2,4-triazole; H2 sdba=4,4'-sulfonyldibenzoic acid), has Co2 "paddlewheel" units connected by sdba ligands to form one-dimensional chains, which are connected by dat to form an anionic three-dimensional structure with cds topology. The one-dimensional channels in the structure contain water molecules, hydronium ions and H2 sdba. The water molecules could be reversibly exchanged with D2 O, CH3 OH and C2 H5 OH molecules; these exchanges were performed in a single-crystal-to-single-crystal manner. Gas sorption studies on the dehydrated compound showed the selective adsorption of CO2 over methane at 195 K. Nonlinear optical measurements indicated that I exhibits a second harmonic generation signal that is approximately one-third that of urea. Studies of polarization versus electric field demonstrated compound I as a potential room-temperature ferroelectric material with a saturation polarization of 0.23 μC cm-2 and remnant polarization of 0.14 μC cm-2 . The dehydrated compound exhibited a simple paraelectric behavior.

Unravelling Mechanistic Aspects of the Gas‐Phase Ethanol Conversion: An Experimental and Computational Study on the Thermal Reactions of MO2+ (M=Mo, W) with Ethanol

The ion/molecule reactions of molybdenum and tungsten dioxide cations with ethanol have been studied by Fourier transform ion-cyclotron resonance mass spectrometry (FT-ICR MS) and density functional theory (DFT) calculations. Dehydration of ethanol has been found as the dominant reaction channel, while generation of the ethyl cation corresponds to a minor product. Cleary, the reactions are mainly governed by the Lewis acidity of the metal center. Computational results, together with isotopic labeling experiments, show that the dehydration of ethanol can proceed either through a conventional concerted [1,2]-elimination mechanism or a step-wise process; the latter occurs via a hydroxyethoxy intermediate. Formation of C2 H5 (+) takes place by transfer of OH(-) from ethanol to the metal center of MO2 (+) . The molybdenum and tungsten dioxide cations exhibit comparable reactivities toward ethanol, and this is reflected in similar reaction rate constants and branching ratios.

One-pot Synthesis of PtSn Bimetallic Composites and Their Application as Highly Active Catalysts for Ethanol Electrooxidation.

PtSn nanoparticles with different molar ratio are fabricated by chemical reduction to form a relatively efficient catalyst for ethanol electrooxidation in an alkaline solution of KOH (1.0 m) containing C2 H5 OH (1.0 m). The surface composition and structure of the as-prepared catalysts are characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray spectroscopy (EDX). Cyclic voltammogram (CV) and chronoamperometric (CA) measurements are used to evaluate the electrochemical activity and stability of the as-prepared catalysts. As the content of Sn in the catalysts changed, the catalysts showed different catalytic activity. The results indicate that the moderate addition of Sn can enhance the catalytic activity of Pt catalyst, and Pt3 Sn1 displays the highest catalytic activity and stability among the as-synthesized PtSn nanoparticles during the electrooxidation of ethanol.

Single-Site Zeolite-Anchored Organoiridium Carbonyl Complexes: Characterization of Structure and Reactivity by Spectroscopy and Computational Chemistry.

A family of HY zeolite-supported cationic organoiridium carbonyl complexes was formed by reaction of Ir(CO)2 (acac) (acac=acetylacetonate) to form supported Ir(CO)2 complexes, which were treated at 298 K and 1 atm with flowing gas-phase reactants, including C2 H4 , H2 , (12) CO, (13) CO, and D2 O. Mass spectrometry was used to identify effluent gases, and infrared and X-ray absorption spectroscopies were used to characterize the supported species, with the results bolstered by DFT calculations. Because the support is crystalline and presents a nearly uniform array of bonding sites for the iridium species, these were characterized by a high degree of uniformity, which allowed a precise determination of the species involved in the replacement, for example, of one CO ligand of each Ir(CO)2 complex with ethylene. The supported species include the following: Ir(CO)2 , Ir(CO)(C2 H4)2 , Ir(CO)(C2 H4), Ir(CO)(C2 H5), and (tentatively) Ir(CO)(H). The data determine a reaction network involving all of these species.

Multifold fluorescence enhancement in nanoscopic fluorophore-clay hybrids in transparent aqueous media.

Valuable emissive properties of organic fluorophores have become indispensable analytical tools in biophotonics, but frequently suffer from low solubilities and radiationless deactivation in aqueous media, that is, in biological ambience as well. In this report, nanoscaled dye-clay hybrids based on laponite, Na0.7 {(Li0.3 Mg5.5 )[Si8 O20 (OH)4 ]}, are taken advantage of to solubilize neutral dyes, which are natively not encountered in water. Previously reported efficiency and solubility bottlenecks of such hybrids can to a large extent be overcome by comparably simple chemical measures, as demonstrated here for two prominent examples, the fluorescent dyes Nile Red and Coumarin 153. On controlled co-adsorption of small bifunctional quaternary ammonium ions (Me3 N(+) C2 H5 OH and Me3 N(+) C2 H5 NH2 ) we observed an outright efficiency boost by an order of magnitude, and a 30-fold brightness gain. Even at higher concentrations, transparency and stability of the hybrid dispersions are retained, rendering them useful for employment as optically functional nanoparticles in bioassays and beyond.

Synthesis, crystal structure, and biological activities of two chiral mononuclear Mn((III)) complexes.

Two new chiral mononuclear Mn((III)) complexes, [MnL((R)) Cl (C2 H5 OH)]•C2 H5 OH () and [MnL((S)) (CH3 OH)2 ]Cl•CH3 OH (), {H2 L = (R,R)-or (S,S)-N,N'-bis-(2-hydroxy-1-naphthalidehydene)-cyclohexanediamine} were synthesized and characterized by various physicochemical techniques. Bond valence sum (BVS) calculations and the Jahn-Teller effect indicate that the Mn centers are in a +3 oxidation state. The statuses of the two complexes in the solution were confirmed as a pair of enantiomers by electrospray ionization, mass spectrometry (ESI-MS) spectrum. The binding ability of the complexes with calf thymus CT-DNA was investigated by spectroscopic and viscosity measurements. Both of the complexes could interact with CT-DNA via an intercalative mode with the order of (R-enantiomer) > (S-enantiomer). Under the physiological conditions, the two compounds exhibit efficient DNA cleavage activities without any external agent, which also follows the order of R-enantiomer > S-enantiomer. Interestingly, the concentration-dependent DNA cleavage experiments indicate an optimal concentration of 17.5 μM. In addition, the interaction of the compounds with bovine serum albumin (BSA) was also investigated, which indicated that the complexes could quench the intrinsic fluorescence of BSA by a static quenching mechanism.

Highly active ppm level organic copper catalyzed photo-induced ICAR ATRP of methyl methacrylate.

A novel photo-induced homogeneous atom transfer radical polymerization (ATRP) system is constructed using an organic copper salt (Cu(SC(S)N(C2 H5 )2 )2 ) as a photo-induced catalyst at 30 °C. Herein, N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDETA) is used as a ligand, ethyl 2-bromophenylacetate (EBPA) as an ATRP initiator, and (2,4,6-trimethylbenzoyl) diphenylphosphine oxide (TPO) as a photo-induced radical initiator to establish an ICAR (initiators for continuous activator regeneration) ATRP using methyl methacrylate (MMA) as a modal monomer. The effect of the concentration of the organic copper on the polymerization is investigated in detail. It is found that well-controlled polymerization can be obtained even with the amount of (Cu(SC(S)N(C2 H5 )2 )2 decreasing to a 1.56 ppm level, with the molecular weight of the resultant polymers increasing linearly with monomer conversion while maintaining a narrow molecular weight distribution (M¯w/M¯n < 1.3).

Quantum chemical study on the atmospheric photooxidation of ethyl acetate

The mechanism for OH radical initiated atmospheric photoxidation reaction of ethyl acetate was carried out by using the density functional theory method. Geometries have been optimized at the B3LYP level with a standard 6-31G(d,p) basis set. The single-point energy calculations have been performed at the MP2/6-31G(d), MP2/6-311++G(d,p), and CCSD(T)/6-31G(d) levels, respectively. All of the possible degradation channels involved in the oxidation of ethyl acetate by OH radicals have been presented and discussed. Among the five possible hydrogen abstraction pathways of the reaction of ethyl acetate with OH radicals, the hydrogen abstractions from the C1–H3 and C2–H5 bonds are the dominant reaction pathways due to the low potential barriers and strong exothermicity. The β-ester rearrangement of IM6 is energetically favorable but is not expected to be important. The α-ester rearrangement reaction and O2 direct abstraction from IM17 are the more favorable pathways and are strongly competitive. In addition, the α-ester rearrangement reaction is confirmed to be a one-step process. Acetic acid, formic acetic anhydride, acetoxyacetaldehyde, and acetic anhydride are the main products for the reaction of ethyl acetate with OH radicals.

Rotational spectrum of ethyl cyanoacetylene (C2H5C≡C–C≡N), a compound of potential astrochemical interest

Context. New radiotelescopes, such as the very sensitive ALMA, will enable the detection of interstellar molecules in much lower concentrations than previously possible. A successful identification of an interstellar molecule requires that laboratory microwave and millimeter-wave spectra are investigated. Several cyanopolyynes and alkynylcarbonitriles have already been detected in the interstellar medium (ISM). Cyanoacetylene (HC≡C–C≡N) is abundant in the ISM and its methyl derivative, 2-butynenitrile (CH3 C≡C–C≡N), is also present. The next derivative, ethyl cyanoacetylene, (2-pentynenitrile C2 H5 C≡C–C≡N) may also be present in interstellar space. Aims. We report the rotational spectrum of the ethyl cyanoacetylene (C2 H5 C≡C–C≡N). This is hoped to facilitate identifying gaseous ethyl cyanoacetylene in the ISM. Methods. We studied the rotational spectrum of C2 H5 C≡C–C≡N between 13 and 116 GHz with the microwave spectrometer of the University of Oslo. The spectroscopic study was augmented by high-level quantum-chemical calculations at B3LYP/cc-pVTZ and CCSD/cc-pVTZ levels of theory. Results. We present for the first time the rotational spectrum of the ethyl cyanoacetylene (C2 H5 C≡C–C≡N). We assigned 342 transitions of the vibrational ground state, accurate values were obtained for rotational and centrifugal distortion constants, and the dipole moment was determined as well.

About the detectability of glycine in the interstellar medium

Context. Glycine, the simplest of aminoacids, has been found in several carbonaceous meteorites. It remains unclear, however, wether glycine is formed in the interstellar medium (ISM) and therefore available everywhere in the Universe. For this reason, radioastronomers have searched for many years unsuccessfully to detect glycine in the ISM. Aims. We provide possible guidelines to optimize the return of these searches. Since, for most of the species observed so far in the ISM, the most abundant isomer of a given generic chemical formula is the most stable one (minimum energy principle (MEP)), we assess whether neutral glycine is the best molecule to search for or whether one of its isomers/conformers or ionic, protonated, or zwitterionic derivatives would have a higher probability of being detected.Methods. The question of the relative stability of these different species is addressed by means of quantum density functional theory (DFT) simulations within the hybrid B3LYP formalism. Each fully optimized structure is verified as a stationary point by means of a vibrational analysis. A comprehensive screening of 32 isomers/conformers of the C2 H5 O2 N chemical formula (neutral, negative, and positive ions together with the corresponding protonated species and the possible zwitterionic structures) is carried out. In the sensitive case of the neutral compounds, more accurate relative energies were obtained by means of high level post Hartree-Fock coupled cluster calculations with large basis sets (CCSD(T)/cc-pVQZ).Results. We find that neutral glycine is not the most stable isomer and, therefore, probably not the most abundant one, which might explain why it has escaped detection so far. We find instead that N-methyl carbamic acid and methyl carbamate are the two most stable isomers and, therefore, probably the two most abundant ones. Among the non-neutral forms, we found that glycine is the most stable isomer only if protonated or zwitterionic if present in interstellar ices. Conclusions. Assuming that MEP can be applied to optimize our search for glycine, our conclusion is that this search will remain extremely difficult with the present instruments and we propose searching instead for other examples among the most stable isomers.

A new weapon for the interstellar complex organic molecule hunt: the minimum energy principle

Context. The hunt for the interstellar complex organic molecules (COMs) supposed to be the building blocks of the molecules at the origin of life is a challenging but very expensive task. It starts with laboratory experiments, associated with theoretical calculations, that give the line frequencies and strengths of the relevant molecules to be identified and finishes with observations at the telescopes.Aims. The present study aims to suggest possible guidelines to optimize this hunt. Levering on the minimum energy principle (MEP) presented in a previous study, we discuss the link between thermodynamic stability and detectability of a number of structures in the important families of amides, sugars and aminonitriles. Methods. The question of the relative stability of these different species is addressed by means of quantum density functional theory simulations. The hybrid B3LYP formalism was used throughout. All 72 molecules part of this survey were treated on an equal footing. Each structure, fully optimized, was verified to be a stationary point by vibrational analysis. Results. A comprehensive screening of 72 isomers of CH3 NO, C2 H5 NO, C3 H7 NO, C2 H4 O2 , C3 H6 O3 and C2 H4 N2 chemical formula has been carried out. We found that formamide, acetamide and propanamide (the first two identified in the Inter-Stellar Medium) are the most stable compounds in their families demonstrating at the same time that the peptide bond > N-C=O at the origin of life is the most stable bond that can be formed. Dihydroxyacetone, whose detection awaits for confirmation, is far from being the most stable isomer of its family while aminoacetonitrile, that has been recently identified, is effectively the most stable species.Conclusions. The MEP appears to be a useful tool for optimizing the hunt for new species by identifying the potentially more abundant isomers of a given chemical formula.

Finite-temperature properties of the muonium substituted ethyl radical CH2MuCH2: nuclear degrees of freedom and hyperfine splitting constants*

The finite-temperature (T) properties of the muonium substituted ethyl radical CH2MuCH2 have been theoretically studied by Feynman path integral quantum Monte Carlo (PIMC) simulations. To derive the ensemble averaged expectation values we have combined the PIMC formalism with an efficient tight-binding (TB) Hamiltonian and a density functional operator of the B3LYP type in the EPRIII basis. The TB operator has been used to calculate the potential energy surface (PES) of the ethyl radical in the doublet ground state, the harmonic and anharmonic vibrational wave numbers as well as several probability density functions of the nuclei. The harmonic linear response approximation, which makes use of the Feynman centroid density, has been adopted to evaluate the anharmonic wave numbers. The large anharmonicities in the nuclear potential lead to bond lengths in thermal equilibrium which exceed the vibrationless parameters at the PES minimum. This enhancement is particularly strong for the C–Mu bond. It is responsible for the suppression of the intramolecular rotation for temperatures below room temperature. In C2 H5 the rotation is allowed down to 10 K. The dissimilar rotational dynamics for H2MuCH2 and C2 H5 has been studied with the help of TB-based probability density functions. The nuclear configurations of CH2MuCH2 and C2 H5, which are populated in thermal equilibrium, have been used to evaluate the isotropic and anisotropic hyperfine splitting (hfs) constants under explicit consideration of the nuclear vibrations and the internal rotation. The hfs constants have been determined with the help of the B3LYP-EPRIII Hamiltonian. The hindered low-temperature rotation in the Mu isomer is responsible for roto-vibrational corrections to the isotropic hfs constants which are smaller than the corrections in C2 H5. The shortcomings of single-configuration approaches for the evaluation of isotropic hfs constants have been demonstrated for both radicals. The ensemble corrections to the isotropic hfs parameters are correlated with fluctuations in the atomic spin densities. Differences in the absolute values of the isotropic hfs parameters in CH2MuCH2 and C2 H5 can be traced back to differences in the nuclear degrees of freedom. The ensemble shift for each isotropic hfs parameter can be explained by characteristic nuclear motions. For this discussion we make use of the distribution functions of the isotropic hfs constants. Roto-vibrational corrections to the anisotropic hfs constants are rather small. PIMC simulations have been performed between 25 and 1000 K, i.e. in a T interval that is large enough to consider nuclear effects beyond zero-point motions. The TB and B3LYP-EPRIII based physical quantities of CH2MuCH2 and C2 H5 have been compared with experimental findings whenever possible.

Reactions of superoxide anion radical with antioxidants and their use in voltammetry

Kinetic parameters were calculated for the electrochemical reduction of oxygen at a glassy-carbon electrode with the generation of superoxide radical anions in a 0.05 M solution of (C2 H5 ) 4NI in dimethylformamide in the presence of fat-soluble antioxidants, retinol and α-tocopherol. A procedure based on the protonation of the radical anion with antioxidant molecules is proposed for the voltammetric determination of antioxidants to determine milligram amounts of retinol and α-tocopherol in model solutions (RSD = 1-2%). The calibration graphs for retinol and α-tocopherol are linear in the concentration ranges 9.7 ×10-5 -2.3 × 10-3 and 6.2 × 10-4 -3.1 × 10-3 M, respectively. The detection limits for retinol and α-tocopherol are 4.8 × 10-5 and 4.1 × 10 -4 M, respectively. The procedure was applied to the determination of the active component (retinol and α-tocopherol) in pharmaceuticals.