Ethanol Radicals Research Articles

Recycling Bonded Nd-Fe-B Magnet Wastes by Chemical Reaction and Its Mechanism.

The difficulty of short-process bonded Nd-Fe-B magnet waste recycling lies in the effective removal of the cured polymer matrix while protecting the magnetic powder. In this study, the polymer matrix in bonded Nd-Fe-B magnet waste was destroyed using sodium hydroxide ethanol solution, and the effect of the recycling process on the magnetic powders was studied. The nonmagnetic polymer matrix was removed, while the magnetic phase was not destroyed. The carbon and oxygen contents of the recycled magnetic powders decreased by 92.96 and 89.30%, respectively, while the MS (saturation magnetization), Mr (remanence), and Hcj (coercivity) values of the recycled magnetic powders were 99.8, 98.5, and 95.9% of the original magnetic powders, respectively. The curing and decomposition processes of the polymer matrix were also analyzed. During the curing process, dicyandiamide and bisphenol A epoxy resin acted as bridges and skeletons, respectively, finally forming a thermosetting three-dimensional network structure. In the alkaline alcohol solution, the bridges and skeletons were destroyed by the free hydroxyl groups and free hydrogen radicals in ethanol, and small molecular products were dissolved in the solution.

The inhibitory and anticancer properties of Annona squamosa L. seed extracts.

Although Annona squamosa Linn. (Annonaceae) has been used in traditional medicine and is known to have several pharmacological properties, its impact on EGFR kinase has not been fully investigated. An assay (biochemical) was used to govern the potential of different A. squamosa seed extracts to scavenge free radicals in petroleum ether, acetone, ethanol, and methanol. We also tested A. squamosa leaf extracts for their ability to inhibit the growth of HEK 293, MCF7, and HepG2 cell lines. The PSE, ASE, ESE, and MSE all contained anti-cancer substances like anethole, cyclopentane, 1,1,3-trimethyl, and phosphonate oxide tributyl, according to phytochemical analysis. ESE extracts from A. squamosa seeds have been selected based on free radical generation probabilities, cytotoxicity studies, and phytochemical analysis. Subsequent insilico studies have been conducted, and the results have shown that interactions between compounds present in ESE extracts and the EGFR kinase are what give these compounds their inhibitory effects. Preliminary phytochemical and pharmacological activities were studied and reported. A. squamosa ESE extracts inhibited the growth of MCF7 cells, and a pharmacokinetic study showed that the compounds anethole, cyclopentane, 1,1,3-trimethyl, and phosphonium oxide tributyl had few undesirable side effects. These substances can be used to both prevent and treat cancer diseases.

Ignition characteristics of nitromethane-doped ethanol in a heated shock tube

Ignition delay times of nitromethane-doped ethanol dual fuels are measured under the micro-combustion engine conditions (8 ​× ​105 ​Pa and 904–1477 ​K). The promotion effect of nitromethane on ethanol ignition is more pronounced at a fuel-lean condition; it first increases and then decreases with increasing blending ratio and temperature. The optimal promotion effect is achieved at 950–1150 ​K with an addition of ~50% nitromethane (mole fraction). A chemical kinetic model is proposed to describe the ignition process of nitromethane-doped ethanol, and can reproduce the measured ignition delay times. Reaction pathway, sensitivity, and rate of production analyses are performed to reveal the promotion mechanisms of nitromethane. The consumption of ethanol via the H-abstraction reactions is enhanced due to the pyrolysis of nitromethane, and the produced ethanol radicals are beneficial to the re-establishment of the radical pool after the first-stage ignition of nitromethane. With decreasing temperature, nitromethane decomposes slowly, while the low-temperature oxidation of ethanol becomes more important. At a moderate temperature, both these two reasons result in a shorter ignition delay time.

Optimizing the Electrochemiluminescence of Readily Accessible Pyrido[1,2‐α]pyrimidines through “Green” Substituent Regulation

AbstractBright and low‐cost emitting organic molecules are very desirable for electrochemiluminescence (ECL). Here, we report a facile one‐step, three‐component reaction of readily available precursors to synthesize pyrido[1,2‐α]pyrimidine derivatives (1–4), all which give off green photoluminescence (PL). In contrast, the electrochemistry and ECL properties of these luminophores are affected by the extent of the conjugation and the nature of the peripheral substituents. Density functional theory (DFT) calculations identified the aromatic chain substitution could extend the conjugation of pyrido[1,2‐α]pyrimidine core and stabilize the electrogenerated radicals required for generation of an excited state, affording pyrido[1,2‐α]pyrimidine 3 the highest ECL activity among the studied samples. ECL in annihilation route confirmed weak emission, but great improvement was made using oxidizing co‐reactant species (benzoate radical from benzoyl peroxide, BPO) with an efficiency of 43 % relative to that of Ru(bpy)3(PF6)2. The pyrido[1,2‐α]pyrimidine 3/BPO system is more robust than those of reducing co‐reactant species [tri‐n‐propylamine radical or 2‐(dibutylamino) ethanol radical] and is one of the highest among the reported organic electrochemiluminophores. ECL spectroscopy revealed that the monomeric excited states were the main species to emit light. Their straightforward, one‐step, green synthesis, and their structure tunability represent significant advantages in the development of readily accessible dyes for PL and especially ECL applications.

Understanding the reaction mechanism of the reactivity of free radicals with graphene oxide

On pulse irradiation of an aqueous solution containing graphene oxide (GO), hydrated electrons (eaq−) are captured by GO in microsecond time scales as suggested recently (ref. 26). We have observed low reactivity of eaq− towards GO as compared to the reported value. It is shown here that the effect of pH (6.8 - 9.2) on the reactivity of eaq− with GO is not significant. The effect of solvent on the reactivity of GO towards free radical was also studied. No significant change in the decay kinetics of MV+• radical in the presence of GO was observed under our experimental conditions. Quenching of eaq− or solvated electron (esol−) in aqueous solution and ethanol, respectively, by GO is confirmed by decrease in the yield of MV+• radical in its presence. In ethanol suspension, the decrease in the rate of formation of MV+• was also observed. It appears that ethanol radicals also transfer electron to MV2+ and GO. Further, to substantiate the formation mechanism of reduced graphene oxide by phenols and amino acids, the pulse radiolysis experiments were carried out and it was observed that phenoxyl radicals as well as tryptophan radicals do not react with GO.

Efficient transformation of DDTs with Persulfate Activation by Zero-valent Iron Nanoparticles: A Mechanistic Study

In this study, persulfate (PS) activation by nano-Fe0 was used to degrade dichlorodiphenyltrichloroethane (DDT), and the mechanism of this process was elucidated with EPR, GC–MS and free-radical quenching studies. It was found that DDT was degraded efficiently in PS/nano-Fe0, and GC–MS analysis showed that benzoic acid, benzyl alcohol, dichlorobenzophenone and 2,2-bis(p-chlorophenyl)-ethane were the dominant products of DDT degradation, while only dechlorination products (DDD and DDE) were observed in nano-Fe0 without persulfate. EPR results showed that persulfate activation by nano-Fe0 led to the production of more sulfate radicals and hydroxyl radicals, which accounted for DDT degradation. But the free radical quenching studies suggested that the addition of ethanol to PS/nano-Fe0 favored the reductive dechlorination of DDT, which was ascribed that the formed ethanol radical (CH(CH3)OH) enhanced the reductive dechlorination of DDT. Furthermore, the nano-Fe0 loading not only affected the degradation efficiency of DDT, but also influenced the intermediate product distribution of DDT degradation in the PS/nano-Fe0 process.

Free Radical Scavenging Reactions of Tetrahydroxyquinone: A Pulse Radiolysis Study

AbstractFree radical induced redox reaction kinetics and mechanism of tetrahydroxy‐1,4‐benzoquinone (THQ) has been studied using pulse radiolysis technique. THQ efficiently scavenged hydrated electron, superoxide radical anion, ethanol radical, hydroxyl radical, azidyl radical, thiocyanate radical anion, sulfate radical anion, haloperoxyl radical, lipid peroxyl radical, tryptophanyl radical and tyrosyl radical. Transient absorption spectra of THQ semiquinone radical anion, THQ radical cation and THQ radical produced with these free radicals and rate constants for these reactions have been studied. A probable mechanism of free radical induced redox reactions of THQ has been proposed. Reaction of THQ with free radicals and cyclic voltammetry measurements suggest its oxidation potentials at 0.81 V and 0.94 V vs NHE. To the best of our knowledge, free radical reactions of THQ have been reported for the first time.

Verification of Radicals Formation in Ethanol–Water Mixture Based Solution Plasma and Their Relation to the Rate of Reaction

Our previous research demonstrated that using ethanol-water mixture as a liquid medium for the synthesis of gold nanoparticles by the solution plasma process (SPP) could lead to an increment of the reaction rate of ∼35.2 times faster than that in pure water. This drastic change was observed when a small amount of ethanol, that is, at an ethanol mole fraction (χethanol) of 0.089, was added in the system. After this composition, the reaction rate decreased continuously. To better understand what happens in the ethanol-water mixture-based SPP, in this study, effect of the ethanol content on the radical formation in the system was verified. We focused on detecting the magnetic resonance of electronic spins using electron spin resonance spectroscopy to determine the type and quantity of the generated radicals at each χethanol. Results indicated that ethanol radicals were generated in the ethanol-water mixtures and exhibited maximum quantity at the xethanol of 0.089. Relationship between the ethanol radical yield and the rate of reaction, along with possible mechanism responsible for the observed phenomenon, is discussed in this paper.

Astaxanthin diferulate as a bifunctional antioxidant

Astaxanthin when esterified with ferulic acid is better singlet oxygen quencher with k2 = (1.58 ± 0.1) 1010 L mol− 1s− 1 in ethanol at 25°C compared with astaxanthin with k2 = (1.12 ± 0.01) 109 L mol− 1s− 1. The ferulate moiety in the astaxanthin diester is a better radical scavenger than free ferulic acid as seen from the rate constant of scavenging of 1-hydroxyethyl radicals in ethanol at 25°C with a second-order rate constant of (1.68 ± 0.1) 108 L mol− 1s− 1 compared with (1.60 ± 0.03) 107 L mol− 1s− 1 for the astaxanthin:ferulic acid mixture, 1:2 equivalents. The mutual enhancement of antioxidant activity for the newly synthetized astaxanthin diferulate becoming a bifunctional antioxidant is rationalized according to a two-dimensional classification plot for electron donation and electron acceptance capability.

Stereoselective C-alkylation of an iron(II) dichloroclathrochelate via free-radical reactions with alcohols

Abstract Free-radical substitution of one of the two chlorine atoms of the tris-dioximate iron(II) dichloroclathrochelate with ethanol and iso-propanol radicals proceeding with high regioselectivity at their α-carbon atoms afforded the monofunctionalized macrobicyclic products, which were characterized both in solution and in solid state by multinuclear one- and two-dimensional NMR spectroscopy and X-ray crystallography, respectively.

Oxidation induced decomposition of ethylene carbonate from DFT calculations – importance of explicitly treating surrounding solvent

The oxidation induced reactions of the common lithium battery electrolyte solvent ethylene carbonate (EC) have been investigated for EC(2) using density functional theory and for selected reaction paths using Møller-Plesset perturbation theory (MP4). The importance of explicitly treating at least one solvent molecule interacting with EC during oxidation (removal of an electron) on the EC oxidation potential and decomposition reactions was shown by comparing oxidation of EC and EC(2). Accuracy of DFT results was evaluated by comparing with MP4 and G4 values for oxidation of EC. The polarized continuum model (PCM) was used to implicitly include the rest of the surrounding solvent. The oxidation potentials of EC(2) and EC(4) were found to be significantly lower than the intrinsic oxidation potential of an isolated EC and also lower than the oxidation potential of EC-BF(4)(-). The exothermic proton abstraction from the ethylene group of EC by the carbonyl group of another EC was responsible for the decreased oxidative stability of EC(2) and EC(4) compared to EC. The most exothermic path with the smallest barrier for EC(2) oxidation yielded CO(2) and an ethanol radical cation. The reaction paths with the higher barrier yielded oligo(ethylene carbonate) suggesting a pathway for the experimentally observed poly(ethylene carbonate) formation of EC-based electrolytes at cathode surfaces.

Free radical scavenging activity of conjugated linoleic acid as single or mixed isomers

Context: Conjugated linoleic acids (CLAs) are a mixture of positional and geometric isomers of linoleic acid (LA) and believed to have many positive biological activities.Objective: The present study was undertaken to assess the antioxidant activity of cis-9, trans-11 and trans-10, cis-12 as single or mixed CLA isomers at two ratios, 1:6 and 1:13 (trans-10, cis-12/cis-9, trans-11).Materials and methods: A microplate reader was used to determine the free radical scavenging properties of CLAs against DPPH radical in ethanol.Results: The kinetic reactions of CLA-DPPH• showed that all tested CLAs have exerted radical scavenging activities in a dose-dependent manner and observed to immediately react and quench DPPH radicals at all tested levels and no lag phase was noticed in CLA-DPPH• reactions. The median inhibitory concentration (IC50) value for cis-9, trans-11 CLA was observed to be more effective than other tested CLA. Total antioxidant capacity (TAC) of all tested CLAs were less effective radical scavengers as compared to vitamin E and butylated hydroxytoluene, although all tested CLAs were quenched a high amount (P < 0.05) of DPPH free radicals.Discussion and conclusion: All tested CLAs have the ability to directly react and quench DPPH free radicals in ethanol. Furthermore, trans-10, cis-12 CLA has greater maximal efficacy than other tested CLAs as free radical scavenger, while cis-9, trans-11 CLA is the most potent isomer to directly react and quench free radicals at low concentrations in the system, suggesting that the free radical scavenging activity of CLA isomers may contribute to their diverse biological activities.

Evidences from electron momentum spectroscopy for ultra-fast charge transfers and structural reorganizations in a floppy molecule: Ethanol

Calculations of electron momentum distributions employing advanced Dyson orbital theories and statistical thermodynamics beyond the RRHO approximation fail to quantitatively reproduce the outermost momentum profile inferred from experiments on ethanol employing high resolution Electron Momentum Spectroscopy [1]. Study of the influence of nuclear dynamics in the initial ground state and final ionized state indicates that this discrepancy between theory and experiment reflects a charge transfer occurring during an ultra-fast dissociation of the ethanol radical cation into a methyl radical and H2C=O-H+.

Radical-Scavenging Activity and Mechanism of Resveratrol-Oriented Analogues: Influence of the Solvent, Radical, and Substitution

Resveratrol (3,5,4'-trihydroxy-trans-stilbene, 3,5,4'-THS) is a well-known natural antioxidant and cancer chemopreventive agent that has attracted much interest in the past decade. To find a more active antioxidant and investigate the antioxidative mechanism with resveratrol as the lead compound, we synthesized 3,5-dihydroxy-trans-stilbene (3,5-DHS), 4-hydroxy-trans-stilbene (4-HS) 3,4-dihydroxy-trans-stilbene (3,4-DHS), 4,4'-dihydroxy-trans-stilbene (4,4'-DHS), 4-hydroxy-3-methoxy-trans-stilbene (3-MeO-4-HS), 4-hydroxy-4'-methoxy-trans-stilbene (4'-MeO-4-HS), 4-hydroxy-4'-methyl-trans-stilbene (4'-Me-4-HS), 4-hydroxy-4'-nitro-trans-stilbene (4'-NO(2)-4-HS), and 4-hydroxy-4'-trifluoromethyl-trans-stilbene (4'-CF(3)-4-HS). The radical-scavenging activity and detailed mechanism of resveratrol and its analogues (ArOHs) were investigated by the reaction kinetics with galvinoxyl (GO(*)) and 2,2-diphenyl-1-picrylhydrazyl (DPPH(*)) radicals in ethanol and ethyl acetate at 25 degrees C, using UV-vis spectroscopy. It was found that the reaction rates increase with increasing the electron-rich environment in the molecules, and the compound bearing o-dihydroxyl groups (3,4-DHS) is the most reactive one among the examined resveratrol analogues. The effect of added acetic acid on the measured rate constant for GO(*)-scavenging reaction reveals that in ethanol that supports ionization solvent besides hydrogen atom transfer (HAT), the kinetics of the process is partially governed by sequential proton loss electron transfer (SPLET). In contrast to GO(*), DPPH(*) has a relatively high reduction potential and therefore enhances the proportion of SPLET in ethanol. The relatively low rate constants for the reactions of ArOHs with GO(*) or DPPH(*) in ethyl acetate compared with the rate constants in ethanol prove that in ethyl acetate these reactions occur primarily by the HAT mechanism. The contribution of SPLET and HAT mechanism depends on the ability of the solvent to ionize ArOH and the reduction potential of the free radical involved. Furthermore, the fate of the ArOH-derived radicals, i.e., the phenoxyl radicals, was investigated by the oxidative product analysis of ArOHs and GO(*) in ethanol. The major products were dihydrofuran dimers in the case of resveratrol, 4,4'-DHS, and 4-HS and a dioxane-like dimer in the case of 3,4-DHS. It is suggested from the oxidative products of these ArOHs that the hydroxyl group at the 4-position is much easier to subject to oxidation than other hydroxyl groups, and the dioxane-like dimer is formed via an o-quinone intermediate.

Probing Nuclear Dynamics in Momentum Space: A New Interpretation of (e, 2e) Electron Impact Ionization Experiments on Ethanol

Calculations of electron momentum distributions for equilibrium geometries, employing advanced Dyson orbital theories and statistical thermodynamics beyond the RRHO approximation, fail to quantitatively reproduce the outermost momentum distribution profile inferred from (e, 2e) electron impact ionization experiments on ethanol employing high-resolution electron momentum spectroscopy. A very detailed study of the influence on this momentum distribution of nuclear dynamics in the initial ground state and in the final ionized state is presented according to a thermal averaging over exceedingly large sets of model structures as well as Born-Oppenheimer molecular dynamical simulations on the potential energy surface of the radical cation. Our results give very convincing albeit qualitative indications that the strong turn-up of the (e, 2e) ionization intensities characterizing the highest occupied molecular orbital (HOMO) of ethanol at low electron momenta is the combined result of (1) the extraordinarily flat nature of the conformational energy map of ethanol, which enables significant departures from energy minima in the ground electronic state, (2) strong anomeric interactions between an oxygen lone pair and the central C-C bond for the minor but significant fraction of conformers exhibiting a hydroxyl torsion angle (alpha) at around 90 degrees, and, last but not least, (3) the possibility to observe with this minor conformer fraction ultrafast and highly significant extensions of the central C-C bond, resulting, in turn, in an enhanced delocalization of the HOMO from the oxygen lone pair region onto the methyl group, immediately after the sudden removal of an electron. This charge transfer appears to occur at the very first stages, that is, within an effective time scale on the order of approximately 10 fs, of an ultrafast dissociation of the ethanol radical cation into a methyl radical and a protonated form of formaldehyde.

Kinetics of Radical Formation during the Mechanical Activation of Quartz

The kinetics of radical formation during the mechanical activation of quartz by wet grinding or sonication was investigated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) as a scavenger. The consumption of DPPH during the sonication of quartz in an ethanol suspension is a zeroth-order process. A linear relationship between the rate constant of the DPPH consumption and the quartz concentration in the suspension indicates that radical formation under sonication increases with the growing total surface area of the quartz particles. Sonication leads to the formation of free radicals by the mechanical activation of the particle surface. The kinetics of the DPPH consumption during wet grinding of quartz in a stirred media mill is described successfully by a modified zeroth-order rate law taking the total surface area of the quartz particles into account. The surface-normalized rate constant of the DPPH consumption decreases from 1.8x10(-7) mol L(-1) h(-1) m(-2) to 4.8x10(-8) mol L(-1) h(-1) m(-2) if the specific surface area of the feed material increases from 0.5 to 84 m2/g. This finding indicates that the breakage of the quartz particles contributes much more to radical formation than does the mechanical activation of the particles in the mill because the breakage rate increases with growing particle diameter. Ethanol but not DPPH was found on the surface of the ground quartz particles. From this finding, it can be concluded that radicals on the surface of the quartz particles react with ethanol, leading to the formation of ethanol radicals and H radicals. DPPH reacts with the H radicals. As a side reaction, radicals can react with oxygen, leading to the formation of peroxides.

Plasma Synthesis of Coated Metal Nanoparticles with Surface Properties Tailored for Dispersion

AbstractA method to produce copper nanoparticles coated with an organic plasma polymer layer is presented. The reaction mechanism for plasma polymerization of ethylene glycol is elucidated, and hydroxyl, methanol and ethanol radicals are shown to be present in the RF discharge. UV radiation is shown to have a significant effect on radical formation. Empirical evidence suggests that nanoparticles exhibit enhanced reactivity. Contact angle measurements of coated particles deposited onto copper collection surfaces show hydrophilic or hydrophobic properties when ethylene glycol or ethane, respectively, is used as the precursor gas. Such properties facilitate dispersion into other media by improving the interaction between the solid and liquid phases.magnified image

Aldehyde oxidase is induced during adipogenesis and is more abundant in visceral when compared to subcutaneous adipose tissue

Background: Aldehyde oxidase (AOX1), an enzyme mainly expressed by hepatocytes, is involved in the catabolism and activation of various drugs, in retinoic acid, ethanol and oxygen radical metabolism. Hyperglycemia stimulates the induction of reactive oxygen species (ROS) in adipocytes that are associated with insulin resistance and an inflammatory response. Because AOX1 is involved in hepatic ROS metabolism, the expression of this enzyme was analysed in primary human adipocytes and subcutaneous and visceral adipose tissue.

Radiolytic Transformation of 2,2′,4′-Trihydroxychalcone

Radiolysis of 2,2',4'-trihydroxychalcone, a natural antioxidant present in fruit and vegetables, was performed in ethanol in the absence or in the presence of dioxygen. The degradation process of chalcone was followed in de-aerated solution by HPLC, NMR, FAB-LSIMS mass spectroscopy and analytical TLC. Under anaerobic conditions, six new products (three couples of diastereoisomers) were identified. Four of them kept the chalcone skeleton with OCH(2)CH(3), CH(OH)CH(3) and H substitutions on C(alpha) and C(beta). Thus the target was the alpha-beta double bond on which ethanol radicals were added. The two other compounds were formed in a second stage and exhibited a cyclization between the substituent on C(beta) and the carbonyl group. In the presence of dioxygen, these reactions were prevented and chalcone was protected. This study was the first step toward understanding of the behavior chalcone in irradiated fruits and vegetables.

Fragmentations of singly charged ethanol cation: An ab initio/RRKM study

A theoretical study was performed to investigate the probable fragmentation channels of a singly charged ethanol radical to represent the signals of m/ e 45, 31, 44, 32, 30 and 28, found in the related mass spectra. The related fragments as implied in the mass spectra should originate from conformers of CH 3CH 2OH + through the H-elimination channels. In order to obtain reasonable rate constants, it is necessary to include the anharmonic frequencies in RRKM method to eliminate the unrealistic rotational mode in the transition state. Most of the C 2H 6O + isomerization reactions require more energy than the abstraction of methyl group and hydrogen atom from CH 3CH 2OH +. Consistent with experimental observation, at low energy, the H-abstraction channels are preferred due to the low energy barriers, while, at high energy, and the methyl abstraction channels are dominated. The fragments with formation energy barriers from high to low are CH 2 CH 2 + , CH 2O +, CH 2CHOH + and CH 2 OH 2 + accordingly, also in a good agreement with experimental observation.