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A density functional theory-assisted synthesis of self-curing epoxy–acrylic resin (EMPA) is described. The calculated quantum chemistry reaction index of the reacting monomer in the basic state, i.e., the radical reaction index (Fk0), is used as a guide to optimize the synthesis conditions. The reliability of the Fk0-assisted synthesis method is confirmed after evaluating the physical appearance, mechanical properties after curing, and thermal stability of the obtained EMPA. The special functional groups of the resin are characterized by Fourier transform infrared spectroscopy to prove the rationality of the reaction mechanism. The cross-sectional morphology characteristics of the cured resin are observed by field-emission scanning electron microscopy. The results show that the closer the molar ratio of monomers in the reaction to the ratio of Fk0 of the reacting monomers, the better the polymerization performance.

In a water ozonation process, dissolved organics undergo two reactions at least: direct ozone attack and oxidation with hydroxyl radicals generated from the ozone decomposition. In the particular case of urban wastewater contaminated with pharmaceuticals, competition between these two reactions can be studied through application of gas&ndash, liquid reaction kinetics. However, there is a lack in literature about kinetic modeling of ozone processes in water specially in photocatalytic ozonation. In this work, lumped reactions of ozone and hydroxyl radicals with total organic carbon have been proposed. Urban wastewater containing a mixture of eight pharmaceutical compounds has been used to establish the kinetic model that simulates the mineralization process. The kinetic model is based on a mechanism of free radical and molecular reactions and the knowledge of mass transfer, chemical reaction rate constants, and radiation transfer data. According to the model, both single ozonation and photocatalytic ozonation present two distinct reaction periods characterized by the absence and presence of dissolved ozone. In the first period (less than 10 min), pharmaceuticals mainly disappear by direct ozone reactions and TOC variation due to these compounds has been modeled according to gas&ndash, liquid reaction kinetics through a lumped ozone-pharmaceutical TOC fast second order reaction. The corresponding rate constant of this reaction was found to change with time from 3 &times, 105 to 200 M&minus, 1 s&minus, 1 with Hatta values higher than 0.3. In the second period (nearly 5 h), competition between direct and hydroxyl radical reactions takes place and a kinetic model based on a direct and free radical reaction mechanism is proposed. Main influencing parameters to be known were: Direct ozone reaction rate constant, catalyst quantum yield, and hydroxyl radical scavengers. The first two take values of 0.5 M&minus, 1 and 5 &times, 10&minus, 4 mol&middot, photon&minus, 1, respectively, while a fraction of TOC between 10% and 90% that changes with time was found to possess hydroxyl radical scavenger nature.

In order to understand the reaction mechanism of lignin pyrolysis, the pyrolysis process of guaiacol (o-methoxyphenol) as a lignin model compound was studied by free radical detection technology (electron paramagnetic resonance, EPR) in this paper. It was proven that the pyrolysis reaction of guaiacol is a free radical reaction, and the free radicals which can be detected mainly by EPR are methyl radicals. This paper proposes a process in which four free radicals (radicals 1- C6H4(OH)O*, radicals 5- C6H4(OCH3)O*, methyl radicals, and hydrogen radicals) are continuously rearranged during the pyrolysis of guaiacol.

Oxidation-responsive emulsions were obtained by stabilizing mineral oil droplets using amphiphilic poly(vinyl pyrrolidone-co-allyl phenyl sulfide) (P(VP-APS)). 1H nuclear magnetic resonance (NMR) spectroscopy revealed that P(VP-APS) whose APS content was 0%, 3.28%, 3.43% and 4.58% were successfully prepared by free radical reaction and the sulfide of APS was oxidized by H2O2 treatment. X-ray Photoelectron Spectroscopy (XPS) also disclosed that the sulfide of APS was oxidized to sulfone by the oxidizing agent. The optical density of copolymer solutions and the interfacial activity of the copolymers markedly decreased by H2O2 treatment possibly because the sulfide of APS was oxidized and the amphiphilicity of the copolymers were weakened. The increase rate of the oil droplet diameter of the emulsions was outstandingly promoted when H2O2 solution (10%, v/v) was used as an aqueous phase. The phase separation of the emulsions was also expedited by the oxidizing agent. The oxidation of APS and the weakened interfacial activity were thought to be a main reason for the demulsification of P(VP-APS)-stabilized emulsions.

The mononuclear copper complexes [Cu{NH=C(OR)NC(OR)=NH}2] with alkoxy-1,3,5-triazapentadiene ligands that have different substituents (R = Me (1), Et (2), nPr (3), iPr (4), CH2CH2OCH3 (5)) were prepared, characterized (including the single crystal X-ray analysis of 3) and studied as catalysts in the mild oxidation of alkanes with H2O2 as an oxidant, pyridine as a promoting agent and cyclohexane as a main model substrate. The complex 4 showed the highest activity with a yield of products up to 18.5% and turnover frequency (TOF) up to 41 h&minus, 1. Cyclohexyl hydroperoxide was the main reaction product in all cases. Selectivity parameters in the oxidation of substituted cyclohexanes and adamantane disclosed a dominant free radical reaction mechanism with hydroxyl radicals as C&ndash, H-attacking species. The main overoxidation product was 6-hydroxyhexanoic acid, suggesting the presence of a secondary reaction mechanism of a different type. All complexes undergo gradual alteration of their structures in acetonitrile solutions to produce catalytically-active intermediates, as evidenced by UV/Vis spectroscopy and kinetic studies. Complex 4, having tertiary C&ndash, H bonds in its iPr substituents, showed the fastest alteration rate, which can be significantly suppressed by using the CD3CN solvent instead of CH3CN one. The observed process was associated to an autocatalytic oxidation of the alkoxy-1,3,5-triazapentadiene ligand. The deuterated complex 4-d32 was prepared and showed higher stability under the same conditions. The complexes 1 and 4 showed different reactivity in the formation of H218O from 18O2 in acetonitrile solutions.

In this paper, a kind of self-curable unsaturated polyester PGA-UP with vinyl groups on the end of molecule chains was synthesized through esterification reaction of glycidol with acrylic acid. The self-curable function of unsaturated polyester was put forward as a new solution to air pollution problems caused by the cross-linking monomer’s volatilization in unsaturated polyesters (UP) industry. The synthetic method, reaction process, molecular structure and self-curing properties were studied. Investigation demonstrates that the unsaturated polyester resin PGA-UP could be synthesized through a two-step process and the liquid product was a mixed outcome of different extent esterification. The unsaturated polyester resin could be self-cured through the free radical reaction of vinyl groups on the end of the molecules when they were initiated by 1% benzoyl peroxide (BPO) at 80°C for 1 hours and 120°C for 2 hours with no cross-linking monomers. The intension strength of the self-cured PGA-UP is 13.5Mpa, close to the 15.6MPa of an usual unsaturated polyester S-UP made in our lab. The self-curable PGA-UP presents good potential application and the research will contribute to improve the environmental problems caused by volatile of cross-linking monomers in unsaturated polyester applications. 1H-NMR and FT-IR were used to characterize.

Reaction of a 2β-bromomethyl penam with triphenyltin hydride gave, via ring expansion of the derived 2β-methyl radical, the corresponding cepham system; a similar process may be in operation during the biosynthetic ring expansion of penicillin N to deacetoxycephalasporin C.1

Homolytic reductive debromination of a 2β-bromomethyl penam by triphenyltin hydride provides, via ring expansion of the derived 2β-methyl radical, the corresponding cepham system; a similar process may explain the biosynthetic ring expansion of penicillins to cephalosporins.

Temperature-dependent free radical reactions were investigated using nitroxyl radicals as redox probes. Reactions of two types of nitroxyl radicals, TEMPOL (4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl) and carbamoyl-PROXYL (3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-N-oxyl), were tested in this paper. Heating a solution containing a nitroxyl radical and a reduced form of glutathione (GSH) caused temperature-dependent decay of electron paramagnetic resonance (EPR) signal intensity of the nitroxyl radical. Heating a solution of the corresponding hydroxylamine form of the nitroxyl radical showed EPR signal recovery. The GSH-dependent reduction of nitroxyl radicals at 70[Deg]C was suppressed by antioxidants, spin trapping agents, and/or bubbling N2 gas, although heating carbamoyl-PROXYL with GSH showed temporarily enhanced signal decay by bubbling N2 gas. Since SOD could restrict the GSH-dependent EPR signal decay of TEMPOL, O2- is related with this reaction. O2- was probably generated from dissolved oxygen in the reaction mixture. Oxidation of the hydroxylamines at 70[Deg]C was also suppressed by bubbling N2 gas. Heating a solution of spin trapping agent, DMPO (5,5-dimethyl-1-pyrroline-N-oxide) showed a temperature-dependent increase of the EPR signal of the hydroxyl radical adduct of DMPO. Synthesis of hydroxyl radical adduct of DMPO at 70[Deg]C was suppressed by antioxidants and/or bubbling N2 gas. The results suggested that heating an aqueous solution containing oxygen can generate reactive oxygen species, mainly O2-.

The prebiotic formation of nucleobases, the building blocks of RNA/DNA, is of current interest. Highly reactive radical species present in the atmosphere under irradiation have been suggested to be involved in the prebiotic synthesis of nucleobases from formamide (FM). We studied several free radical reaction pathways for the synthesis of pyrimidine bases (cytosine, uracil, and thymine) from FM under cold conditions. These pathways are theoretically determined using density functional theory (DFT) computations to examine their kinetic and thermodynamic feasibilities. These free radical reaction pathways share some common reaction types such as H-rearrangement, (•)H/(•)OH/(•)NH2 radical loss, and intramolecular radical cyclization. The rate-determining steps in these pathways are characterized with low energy barriers. The energy barriers of the ring formation steps are in the range of 3-7 kcal/mol. Although DFT methods are known to significantly underestimate the barriers for addition of (•)H radical to neutral species, many of these reactions are highly exergonic with energy release of -15 to -52 kcal/mol and are thus favorable. Among the suggested pathways for formation of cytosine (main route, routes 7a and 1a), uracil (main route, routes 7b and 1b), and thymine (main route and route 26a), the main routes are in general thermodynamically more exergonic and more kinetically favored than other alternative routes with lower overall energy barriers. The reaction energies released following formation of cytosine, uracil, and thymine from FM via the main radical routes amount to -59, -81, and -104 kcal/mol, respectively. Increasing temperature induces unfavorable changes in both kinetic and thermodynamic aspects of the suggested routes. However, the main routes are still more favored than the alternative pathways at the temperature up to the boiling point of FM.

Analogs of the seco-cyclopyrroloindoline (seco-CPI), the DNA alkylation pharmacophore of CC-1065 and the duocarmycins, can be prepared through a 5-exo-trig radical cyclization of a free radical and a 3-chloro-2-allylic moiety. This manuscript reports an unexpected discovery that, depending on the structure and stability of the free radical, the cyclization process leads to the production of an appreciable amount of seco- cyclopropyltetrahydroquinolines 7a-d along with the seco-cyclopropoyltetra- hydroindoline products (6a-e). For instance, free radical reaction of the bromoallylic chloride 5a produced an equal amount of 6-benzyloxy-N-t-butoxycarbonyl-3- (chloromethyl)furano[e]indoline (6a), and 7-benzyloxy-N-t-butoxycarbonyl-3-chloro- 1,2,3,4-tetrahydrofurano[f]quinoline (7a). Three other examples that produced mixtures of indoline and quinoline products are provided. In only one of the examples reported in this manuscript, the 6-benzyloxy-N-t-butoxycarbonyl-3-(chloromethyl)benzo[e]indoline, was a seco-CBI precursor 6e formed exclusively, consistent with literature precedents.

A highly regioselective radical addition of N,N-dichlorobenzenesulfonamide (dichloramine-B) to 1-alkenes is achieved at -78 degrees C by the use of triethylborane as a radical initiator. The reaction of 1,3-dienes with N,N-dichlorosulfonamide in the presence of Et(3)B regioselectively provides N-chloro-N-allylamide derivatives. N-chloro-N-allylamides thus obtained react with a variety of alkenes to furnish pyrrolidine derivatives in good yields. A radical annulation reaction among N,N-dichlorosulfonamide, 1,3-dienes, and alkenes has been developed.

Free radical-initiated peptide sequencing (FRIPS) mass spectrometry derives advantage from the introduction of highly selective low-energy dissociation pathways in target peptides. An acetyl radical, formed at the peptide N-terminus via collisional activation and subsequent dissociation of a covalently attached radical precursor, abstracts a hydrogen atom from diverse sites on the peptide, yielding sequence information through backbone cleavage as well as side-chain loss. Unique free-radical-initiated dissociation pathways observed at serine and threonine residues lead to cleavage of the neighboring N-terminal C_α–C or N–C_α bond rather than the typical Cα–C bond cleavage observed with other amino acids. These reactions were investigated by FRIPS of model peptides of the form AARAAAXAA, where X is the amino acid of interest. In combination with density functional theory (DFT) calculations, the experiments indicate the strong influence of hydrogen bonding at serine or threonine on the observed free radical chemistry. Hydrogen bonding of the side-chain hydroxyl group with a backbone carbonyl oxygen aligns the singly occupied π orbital on the β-carbon and the N–C_α bond, leading to low-barrier β-cleavage of the N–C_α bond. Interaction with the N-terminal carbonyl favors a hydrogen-atom transfer process to yield stable c and z• ions, whereas C-terminal interaction leads to effective cleavage of the C_α–C bond through rapid loss of isocyanic acid. Dissociation of the C_α–C bond may also occur via water loss followed by β-cleavage from a nitrogen-centered radical. These competitive dissociation pathways from a single residue illustrate the sensitivity of gas-phase free radical chemistry to subtle factors such as hydrogen bonding that affect the potential energy surface for these low-barrier processes.

Smog chamber/FTIR techniques were used to study the Cl atom initiated oxidation of CF 3 OCF 2 H in 700 Torr of N 2 /O 2 at 295±2 K . Atmospheric oxidation of CF 3 OCF 2 H proceeds via the formation of CF 3 OCF 2 radicals. The atmospheric fate of CF 3 OCF 2 radicals is addition of O 2 to give CF 3 OCF 2 O 2 radicals. In the atmosphere CF 3 OCF 2 O 2 radicals are converted via COF 2 and CF 3 OH into CO 2 and HF. Relative rate techniques were used to measure k( Cl + CF 3 OCF 2 H )=(2.3±0.3)×10 −17 cm 3 molecule −1 s −1 . The results are discussed with respect to the atmospheric degradation and environmental impact of CF 3 OCF 2 H.

Degradation rates ranging from 0.22 ± 0.11 to 1.52 ± 0.50 mg/L-h were measured for ethylene glycol in riboflavin solutions exposed to natural sunlight. Significant degradation rates were noted in systems using 6 and 10 mg/L riboflavin at pH values of 4, 7, and 10. No significant degradation was found in systems using methylene blue as the photosensitizing agent. Possible mechanisms for ethylene glycol degradation include a combination hydrogen or electron abstraction by an excited photosensitizer and reaction with singlet oxygen or reaction with superoxide radicals.

Pyrroloquinone ring systems are important structural units present in many biologically active molecules including a number of marine alkaloids. For example, they are found in a series of marine metabolites, such as tsitsikammamines, zyzzyanones, wakayin, and terreusinone. Several of these alkaloids have exhibited antimicrobial, antimalarial, antifungal, antitumor, and photoprotecting activities. Synthesis of pyrroloquinone unit is the key step in the synthesis of many of these important organic molecules. Here, we present a ceric (IV) ammonium nitrate (CAN) mediated oxidative free radical cyclization reaction of 1,3-dicarbonyl compounds with aminoquinones as a facile methodology for making various substituted pyrroloquinones. 1,3-dicarbonyl compounds used in this study are ethyl acetoacetate, acetylacetone, benzoyl acetone, andN,N-dimethyl acetoacetamide. The aminoquinones used in this study are 2-(benzylamino)naphthalene-1,4-dione and 6-(benzylamino)-1-tosyl-1H-indole-4,7-dione. The yields of the synthesized pyrroloquinones ranged from 23–91%.

The reactions of the OH radicals and the Cl atoms with 3-hydroxy 2-butanone (3H2B) and 4-hydroxy 2-butanone (4H2B) were investigated in the gas-phase using relative rate method. The kinetic study on the OH-reactions was carried out using a Pyrex atmospheric chamber at 600–760 Torr of purified air. The temperature ranges were 298–338 K for 3H2B and 278–333 K for 4H2B. A slight negative dependence of the rate coefficients behaviour was observed and the Arrhenius expressions obtained are (in cm 3 molecule −1 s −1 ): k 3H2B(OH) = (1.25 ± 0.20) × 10 −12 exp(612 ± 50/T −1 ) and k 4HB (OH) = (7.50 ± 2.0) × 10 −12 exp(196 ± 20/T −1 ). Rate coefficients for the gas-phase reactions of Cl atoms with 3H2B and 4H2B were measured using an atmospheric simulation chamber made of Teflon at 298 ± 3 K and 760 Torr. The obtained rate coefficients (in cm 3 molecule −1 s −1 ) were (4.90 ± 0.45) × 10 −11 and (1.45 ± 0.15) × 10 −10 for 3H2B and 4H2B, respectively. The obtained data are presented, compared to those reported in the literature and the reactivity trends discussed. The estimated tropospheric lifetimes obtained in this work suggest that once emitted into the atmosphere, 3H2B and 4H2B will be oxidized near the emission sources.

Sodium hypochlorite solutions are used to treat membranes prepared from a polymeric blend containing poly(vinyl pyrrolidone) (PVP) to increase their water permeability. Sodium hypochlorite affects the membrane material in such a way that PVP is selectively removed from the membrane matrix. The mechanism of the reaction between hypochlorite and PVP is investigated by several chemical analysis techniques of the reaction products. Strong indications are found that the reaction involves chain scission of PVP according to a radical mechanism.

International audience; Synthesis of highly end-functionalized polyethylene chains was accomplished using both coordination chemistry and radical mediated thiol?ene chemistry. A vinyl end-terminated polyethylene (Mn =1440 g·mol?1, PDI = 1.8) with a functionalization rate of 100% was synthesized using a P,O-chelated catalyst [Ni\Ph2PC(COOEt)═C(C6H5)O\Ph(PPh3)]. Thiol?ene reactions were subsequently undertaken between vinyl-terminated polyethylene and the thiol-containing molecules thioglycolic acid, 2-mercaptoethanol, 1-thioglycerol, chloropropanethiol, and methyl thioglycolate. A range of end-functionalized polyethylenes was thus prepared using simple reaction conditions and exhibiting degrees of functionalization higher than 93%.

金沢大学大学院自然科学研究科生理活性物質科学, 金沢大学薬学部

1o páginas, 1 figura, 8 esquemas., Readily available proline derivatives can be transformed in one step into β-iodinated iminosugar-based nucleosides, under very mild conditions. The method couples a tandem radical decarboxylation–oxidation–β-iodination to the addition of nitrogen bases. The iodo group is introduced into the previously unfunctionalized 3-position. The resultant β-iodo derivatives are useful precursors of highly functionalizednucleoside analogues., This work was supported by the Spanish Ministerio de Educación y Ciencia (MEC) and Ministerio de Ciencia e Innovación (MICINN), Investigation Programmes CTQ2006-14260/PPQ and CTQ2009-07109 of the Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica. The authors also acknowledge financial support from the European Regional Development Funds (FEDER funds). D. H. thanks the MEC for a fellowship and the Gobierno de Canarias (ACIISI)-BIOSIGMA SL for a research contract.

11 páginas., Common amino acid derivatives can be transformed in one-step fashion into N-azanucleosides. The method is a sequential process initiated by a domino radical decarboxylation/oxidation reaction; an acyliminium ion is formed as an intermediate and can be trapped by nitrogen bases (purines, pyrimidines, and benzotriazole). The mildness of the reaction conditions and the good yields obtained make this procedure an interesting alternative to the conventional processes. Good stereoselectivities were obtained with 4-(silyloxy)proline derivatives as substrates.

The kinetics of the heterogeneous reaction of OH radicals with 15 polycyclic aromatic hydrocarbons (PAHs) present in laboratory generated simulated kerosene combustion soot was studied at T = 290 K in a low pressure discharge-flow reactor combined with an electron-impact mass spectrometer. The kinetics of soot-bound PAH consumption in reaction with OH were monitored using off-line HPLC measurements of their concentrations in soot samples as a function of time of exposure to OH. Concentration of OH radicals in the gas phase was measured by mass spectrometry. The first-order rate constants measured for the individual PAH at T = 290 K ranged from 0.02 to 0.04 s −1 and were found to be independent of the OH concentration ([OH] = (0.34–2.5) × 10 12 molecule cm −3 ) and of the molecular structure of the PAH. In addition, the uptake coefficient of OH on soot surface and the diffusion coefficient of OH in He were measured to be 0.19 ± 0.03 (calculated with geometric surface area) and (615 ± 80) Torr cm 2 s −1 , respectively. Comparison of the results on the PAH + OH reaction to those from previous studies carried out on different carbonaceous substrates, indicates probable dependence of the heterogeneous reactivity of PAH toward OH on the substrate nature. Rapid reaction with OH can be an important potential pathway of the atmospheric degradation of non-volatile PAH present mainly in the particulate phase in the atmosphere.

Reaction of thiomaleic anhydride with triphenylphosphine gives the title compound which undergoes reaction with a variety of aldehydes to give a range of alkylidene thiomaleic anhydrides (substituted monothio itaconic anhydrides). Subsequent treatment with tert-butoxycarbonylamino-substituted thiols, or under radical conditions with tert-butoxycarbonylamino-substituted alkyl halides results in a series of substituted monothiomaleic anhydrides, that on exposure to trifluoroacetic acid and then base lead to thiocarboxyl substituted 1,4-thiazepin-5-ones and piperidinones, respectively, that are ultimately trapped by reaction with 2,4-dinitrobenzenesulfonamides to give the corresponding amides.

International audience; The inhibition effect of toluene on the kinetics of n-alkane pyrolysis has been well-known for a long time. However, most studies were performed at high-temperature−low-pressure conditions. The present study investigates a wider range of experimental pressures and temperatures (from 0.001 to 700 bar and from 350 to 600 °C). To account for those, a kinetic model based on free-radical reactions was developed. This model was tested against available literature data for the low-pressure range and against new experiments for the high-pressure range. Whatever the temperature and pressure, it arises that toluene has indeed an inhibitive effect on the pyrolysis of n-octane. This effect is explained by the formation of benzyl radicals stabilized by resonance, via hydrogen-transfer reactions, that leads to new termination reactions. However, this inhibition will be significantly modulated as a function of the pressure, temperature, and reaction progress, from strong to very weak. Our paper describes the mechanistic reasons for this change in the extent of the inhibition effect and proposes an integrated model for the kinetic effects of monoaromatic hydrocarbons on n-alkanes during pyrolysis.

International audience; Various xanthates can be added to N-vinyl phthalimide with little formation of oligomers, if the xanthate is used in excess and the medium slightly diluted. The adduct xanthates thus obtained can in turn undergo radical additions to numerous olefins, providing a convergent and modular access to densely functionalized amines. © 2010 Elsevier Ltd.

International audience; Radical chain end functionalization of polystyrene previously prepared by NMP using the SG1 nitroxide was investigated. Hydroxy-functional polystyrenes were easily prepared by two different pathways: via an exchange with TEMPO nitroxide followed by a Zn/AcOH reduction or via a radical hydroxylation using the in situ preparation/reduction of the corresponding hydroperoxide. The introduction of a bromine end group was performed by radical bromination under mild conditions using ethyl 2-bromoisobutyrate as bromine transfer agent. The latter polymer was further reacted with NaN3 and also used as a macroinitiator to prepare PS-b-PMMA by ATRP to confirm the chemical post-transformation. Azide-functional polystyrenes were also prepared by a one-step radical azidation reaction using ethanesulfonyl azide. In all cases, the chemical transformations were followed by both liquid chromatography at the critical condition in pure eluent and Maldi-Tof MS.

The homolysis of peracetic acid (PAA) as a relevant source of free radicals (e.g., *OH) was studied in detail. Radicals formed as a result of chain radical reactions were detected with electron spin resonance and nuclear magnetic resonance spin trapping techniques and subsequently identified by means of the simulation-based fitting approach. The reaction mechanism, where a hydroxyl radical was a primary product of O-O bond rupture of PAA, was established with a complete assessment of relevant reaction thermochemistry. Total energy analysis of the reaction pathway was performed by electronic structure calculations (ab initio and semiempirical methods) at different levels and basis sets [e.g., HF/6-311G(d), B3LYP/6-31G(d)]. Furthermore, the heterogeneous MnO2/PAA system was tested for the elimination of a model aromatic compound, phenol from aqueous solution. An artificial neural network (ANN) was designed to associate the removal efficiency of phenol with relevant process parameters such as concentrations of both the catalyst and PAA and the reaction time. Results were used to train and test ANN to identify an optimized network structure, which represented the correlations between the operational parameters and removal efficiency of phenol.

The study of the reaction with MeONa/MeOH of chlorinated γ-lactams, prepared from the atom transfer radical cyclization of N-allyl-α-perchloroamides, has been extended to the case of substrates carrying an exo halogen atom on a branched carbon. Only with secondary exo C–Cl groups, that are not located on a fused ring, does the functional rearrangement follow the typical transformation route, which with trichloro-lactams can proceed further to give 4-alkylidene derivatives. From a practical point of view, the outcome of the reaction with di- or trichloro N-cinnamylamides is synthetically valuable, affording the 5-methoxy-1H-pyrrol-2(5H)-one or 3-benzylidenepyrrolidine-2,5-dione, respectively, in good to excellent yield.

International audience; Cobalt-mediated radical coupling (CMRC) is successfully applied to poly(vinyl acetate) (PVAc) and poly(N-vinylpyrrolidone) (PNVP) precursors for the first time. The coupling process is based on addition of isoprene onto polymer chains preformed by controlled radical polymerization with cobalt complexes (CMRP). The extents of coupling were high (>90%) to moderate (75−80%) for PVAc and PNVP precursors, respectively. Effects of the length of the polymer precursors and conditions used in the polymerization step on the coupling efficiency are discussed. Mass spectrometry (MS) and nuclear magnetic resonance (NMR) analyses conducted on the coupling products demonstrate the preferential insertion of two isoprene units in the final polymers. The CMRC mechanistic proposal, supported by DFT calculations, is based on this microstructure feature. Finally, illustration of the macromolecular engineering potential of this technique is given by the preparation of symmetrical PVAc-b-PNVP-b-PVAc triblock copolymers starting from the corresponding PVAc-b-PNVP-[Co] diblock copolymer.

The mechanistic details of Mn(OAc)(3)-based oxidative free-radical additions and cyclizations are reviewed. The mechanisms of electron transfer to generate radicals, electron transfer to convert the radicals to oxidized products, and further oxidation of the products are covered.

5 páginas, 2 figuras, 2 tablas, 6 esquemas., An unusual scission–rearrangement process, which couples radical and ionic reactions, was observed with galactofuranose derivatives. This one-pot procedure afforded, in good yields, highly functionalized 1,4-dioxanes, which could be considered as six-membered-ring sugar analogues. The synthesis of C-glycoside analogues is also possible with this methodology., This work was supported by the Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica, and Ministerio de Educación y Ciencia, Spain (Research Program CTQ2006-14260/PPQ). We also acknowledge financial support from FEDER funds. D. H. thanks the Gobierno de Canarias (Consejería de Industria) – CSIC for a research contract.

Homobenzonorbornadiene and benzobarrelene were reacted with dimedone/acetylacetone and Mn(OAc)(3) in the presence of Cu(OAc)(2) in acetic acid. Mainly rearranged products having a [2.2.2]skeleton and the nonrearranged dihydrofuran derivatives were obtained. These observations clearly indicated that the second oxidation takes place before the cyclization reaction. Furthermore, intramolecular tandem oxidations were observed where unusually oxyl radicals attack the double bond to form the products. The mechanism of the formation of the products is discussed. (C) 2008 Elsevier Ltd. All rights reserved.

The electrochemical reductive cyclisation of unsaturated organic halides in the presence of Ni(II) complexes as catalysts was examined in aprotic solvents such as DMF and in protic solvents such as ethanol, butanol or ethanolewater mixtures. The presence of the alcohol media enhanced the rate of recycling of the catalytic species., La cyclisation réductive électrochimique d’halogénures insaturés en présence de complexes de Ni(II) comme catalyseurs a été examinée dans des solvants comme le DMF et dans des solvants protiques comme l’éthanol, le butanol ou des mélanges éthanol-eau. La présence du milieu alcoolique augmente la vitesse du recyclage des espèces catalytiques., Fundação para a Ciência e a Tecnologia (FCT)

The diastereoselective MnIII-promoted radical addition of β-oxoesters 1 onto N-cinnamoyloxazolidinones 2 afforded 2,3-dihydrofurans 3. After catalytic hydrogenation of the C=C bond, followed by reductive removal of the chiral auxiliary, the resulting enantiopure tetrahydrofurans 5 were transformed in two steps into naturally occurring (–)-virgatusin and (+)-urinaligran and two other, nonnatural, tetrasubstituted THF lignans. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

The degradation of vitamin E by aerobic bacterial communities, isolated from marine sediment and microbial mat samples, was investigated. PCR-DGGE profiles and cloning/sequencing experiments revealed that biodegradation of vitamin E in sediments is mainly carried out by strains belonging to the genera Idiomarina and Bacillus for which the DGGE pattern matched with the pattern obtained from the second sediment subculture. Biodegradation processes appeared to involve an initial ω-oxidation of the isoprenoid side chain and subsequent β-oxidation sequences affording 2,5,7,8-tetramethyl–2(2’-carboxyethyl)-6-hydroxychroman (α-CEHC). This compound was not accumulated at the end of the growth, showing that the bacterial degradation of vitamin E is not limited to its isoprenoid side chain. In cultures still containing residual sediment, the presence of metabolites with a shortened side chain and an opened chroman ring (e.g., α-tocopheronolactone and α-tocopherylhydroquinonolactone) attested to the simultaneous involvement of biodegradation and autoxidation processes. The induction of autoxidation during these incubations was attributed to some of the sediment components, which could act as catalysts of free radical reactions. In oxic environments, the combination of free radical oxidation and aerobic biodegradation processes should result in a very fast degradation of vitamin E. Different pathways are proposed to explain the formation of the different compounds resulting from these interactions.

In this study, we present the synthesis of poly-MMA macroperoxy initiators obtained by the ATRP of MMA with bromo methyl benzyl t-butyl peroxy ester (t-BuBP) as an initiator, and CuX (X:Br or Cl)/2,2'-bipyridine (bpy) as a catalyst system at 0, 20, 30 and 40C. The peroxygen groups do not decompose during the ATRP reaction, because low reaction temperatures used for the ATRP reaction are not enough to decompose them. The peroxygen groups of poly-PMMA macroperoxy initiators can lead them to react with a monomer by using appropriate reaction conditions to obtain the block or graft copolymers. For this purpose, poly-MMA macroperoxy initiators were used to synthesize poly(MMA-b-S) block copolymers with S and used for graft copolymerization of polybutadiene (PBd) and natural rubber (RSS-3) to obtain crosslinked poly(MMA-g-PBd) and poly(MMA-g-RSS-3) graft copolymers. Swelling ratio values of the crosslinked graft copolymers in CHCl3 were calculated. The characterizations of the polymers were achieved by FT-IR, 1H-NMR, GPC, DSC, SEM, and the fractional precipitation () techniques. The reaction schemes were also performed using the HYPERCHEM 7.5 program. The mechanical properties of the products were investigated.

In the reaction between perfluoroolefins and perfluoroalkylhypofluorites the existence of two different free radical reaction mechanisms is demonstrated by the presence of characteristic byproducts. These kinetic schemes can be experimentally controlled by tuning the hypofluorite concentration in the reaction media. In particular, in the reactions between trifluoromethyl hypofluorite and highly reactive perfluoroolefins like CF 2 CFOCF 3 and CF 2 CF 2 , the free radical oligomerization and dimerization products can be suppressed by utilizing the opportune experimental conditions. The pure perfluorinated ethers obtained, having low Ostwald coefficient, can be utilized as contrast agents for diagnostic ultrasound imaging injectable microbubbles composition.