Presence Of Organic Peroxides Research Articles

A Facile Highly Selective Anti‐Markovnikov Hydroamination of Vinyl Pyridines by Free Radical Oxidation

AbstractIn this paper, we report a new and facile protocol for anti‐Markovnikov hydroamination of vinyl pyridines under mild condition. In the presence of organic peroxide, pyridylethylation of a wide variety of aryl/alkyl amines with different substituent and electronic characteristics by intermolecular anti‐Markovnikov hydroamination was successfully carried out. Furthermore, moderate to excellent yields were obtained along with high selectivity through condition optimization. The highest yield of target product can reach 93 % in gram‐scale reaction. On the basis, we proposed a kind of aza‐Michael‐type free radical addition mechanism, which was well supported by deuterium labeling studies and reference experiments.

Organic Peroxide-Sensing Repressor OhrR Regulates Organic Hydroperoxide Stress Resistance and Avermectin Production in Streptomyces avermitilis.

The bacterium Streptomyces avermitilis is an industrial-scale producer of avermectins, which are important anthelmintic agents widely used in agriculture, veterinary medicine, and human medicine. During the avermectin fermentation process, S. avermitilis is exposed to organic peroxides generated by aerobic respiration. We investigated the role of MarR-family transcriptional regulator OhrR in oxidative stress response and avermectin production in S. avermitilis. The S. avermitilis genome encodes two organic hydroperoxide resistance proteins: OhrB1 and OhrB2. OhrB2 is the major resistance protein in organic peroxide stress responses. In the absence of organic peroxide, the reduced form of OhrR represses the expression of ohrB2 gene by binding to the OhrR box in the promoter region. In the presence of organic peroxide, the oxidized form of OhrR dissociates from the OhrR box and the expression of ohrB2 is increased by derepression. OhrR also acts as a repressor to regulate its own expression. An ohrR-deletion mutant (termed DohrR) displayed enhanced avermectin production. Our findings demonstrate that OhrR in S. avermitilis represses avermectin production by regulating the expression of pathway-specific regulatory gene aveR. OhrR also plays a regulatory role in glycolysis and the pentose phosphate (PP) pathway by negatively controlling the expression of pykA2 and ctaB/tkt2-tal2-zwf2-opcA2-pgl.

Influence of the Coordination Surrounding of Co(II)- and Co(III)-Tetraphenylporphyrins on Their Destruction Processes in the Presence of Organic Peroxides

The interaction of Co(II)- and Co(III)-5,10,15,20-tetraphenylporphyrins with tert-butylhydroxyperoxide and di-tert-butylhydroxyperoxide in benzene at 298 K were studied by spectrophotometry and 1H NMR spectroscopy. Kinetic parameters of the destruction reactions of porphyrin macrocycle depending on the nature of peroxide the valence of cobalt cation, and the presence and nature of axial ligands were calculated. Products of consecutive decomposition of tetrapyrrole macrocycle to monopyrroles were determined by mass spectrometry.

Heterophasic Polypropylene Copolymer Grafted with Itaconic Acid: Molecular Structure Analysis Through Fractionation Techniques

SummaryThe functionalization of polypropylene (PP) through the grafting of unsaturated polar monomers such as maleic anhydride (MAH), acrylic acid and its derivatives, in the presence of organic peroxide as initiator, has received much attention over the past decades. However, up to now, only few studies have been reported on the effect of these polar monomers on crystallization and how they are distributed in the polymeric chain. In the present work heterophasic polypropylene copolymer was grafted with itaconic acid (AIt) using reactive extrusion. The main objective of this work was to evaluate the influence of itaconic acid in the rubber and crystalline phases in samples of PP. The separation of the different phases by xylene solubles analysis showed that the acid has preference to incorporate in the rubber fraction. The amount of itaconic acid was determinate by FTIR. It was concluded that the addition of peroxide and itaconic acid to the polymer causes changes of chemical and structural order in the generated material. The results showed a narrowing in the profile of crystallization of the samples analyzed by CRYSTAF resulting of a higher interaction between crystalline and amorphous phases, due to the presence of hydrogen bridges arising from the grafted acid.

Crosslinking of high‐density polyethylene in the presence of organic peroxides

AbstractThe crosslinking efficiency of various commercially available organic peroxides (dicumyl peroxide, O,O‐t‐butyl O‐2‐ethylhexylperoxycarbonate, t‐butyl peroxybenzoate, t‐butyl 3,5,5‐trimethylperoxyhexanoate, and t‐butyl 2‐ethylperoxyhexanoate) was tested on high‐density polyethylene (HDPE) in its molten state. The variations of the concentrations of the peroxides versus the crosslinking extent were plotted for these peroxides, and the values were compared. Dicumyl peroxide was found to be the best crosslinking agent for HDPE. The efficiency of the HDPE crosslinking with each peroxy derivative was analyzed on the basis of the behavior of the radicals generated from it. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 75–81, 2004

Fungal laccase grafts acrylamide onto lignin in presence of peroxides

Laccase (EC 1.10.3.2) from the white-rot basidomycete Trametes versicolor in the presence of organic peroxides, particularly dioxane peroxide, tetrahydrofuran peroxide and t-butylhydroperoxide, initiated free-radical copolymerization of acrylamide and lignin. Hydrogen peroxide showed no such effect. Both the type of peroxide and the catalytic efficiency of the enzyme were important to ensure a significant yield of copolymerisate and a high rate of acrylamide incorporation into a lignin backbone. The mechanism of the enzymatic grafting is discussed.

Some Properties of Blends Based on High Density Polyethylene Grafted with Di-2-Ethyl-Hexyl Fumarat

Blends based on high density polyethylene (MFI=0.3 g/10 min) and low density polyethylene grafted with di-2-ethyl-hexyl fumarate are presented. These blends were obtained through component homogenization, in different proportions, on a Berstorff laboratory roll-mill, for 10 minutes at 180°C. Low density polyethylene (MFI=2.0 g/10min) grafting was carried out in polymer melt, through radicalic initiation, in the presence of organic peroxides, at a temperature of 140—160°C. The content of the monomer grafted on polymer chain was determined through IR absorption spectrophotometry using the absorption band of 1735 cm−1. From the experimental, obtained blends plates, 1 mm thick, were manufactured with the purpose of determining the main tensile properties. For the respective blends melt flow index evolution were followed.

Hydroperoxynaphthalimide Derivative‐mediated Oxidation of Heme Proteins on Photoirradiation: Horseradish Peroxidase

Abstract— Horseradish peroxidase (HRP) was photoirradiated in the presence of organic peroxide (1, hydroperoxynaphthalimide derivative) at around 353 nm and 0°C. This compound bound to a heme pocket of HRP as shown by its inhibitory effect on catalysis by HRP (Ki= 5.5 times 10−5 M) and subsequently it formed an intermediate in the same way as H202. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) suggested cleavage of the peptide chain of HRP on photoirradiation with 1. From CD spectra and SDS‐PAGE, it was presumed that the destruction of both secondary structure and heme of the enzyme occurred to some extent upon photoirradiation, which resulted in a decrease in the catalytic activity. The absorption spectra also suggested that the heme group of the enzyme was destroyed, and the fluorescence spectra showed that the Trp residue in the photoirradiated HRP was oxidized to N‐formylkynurenine by a hydroxyl radical generated from 1. Energy transfer from the excited naphthalimide moiety or hydrogen abstraction also seemed to make some contribution to the alteration of the heme group.

Asbestos induced oxidative injury to DNA.

DNA-damaging effects of asbestos in the presence of organic peroxides and hydroperoxides were investigated. The destabilization of the secondary structure of DNA, damage to deoxyribose sugar and DNA fidelity were measured, respectively, by S-1 nuclease hydrolysis, the formation of thiobarbituric acid (TBA)-reacting species and a melting temperature (Tm) profile using calf thymus DNA. S-1 nuclease hydrolysis and Tm determinations have shown that the presence of benzoylperoxide (BOOB), cumene hydroperoxide (COOH) or tertiary-butyl hydroperoxide (t-BOOH) increased asbestos-mediated DNA damage by a large factor compared either to asbestos alone or to peroxide or hydroperoxide alone. However, no formation of TBA-reacting species could be observed in this system. The quenchers of reactive oxygen species (ROS) afforded protection against DNA damage. These results suggest that asbestos in the presence of organic peroxides and hydroperoxides damage the DNA which is mediated by the generation of oxygen free radicals. The significance of these results in relation to the development of cancer of the respiratory tract among the asbestos exposed population is discussed.

The effects of enzymes on the photobleaching of fluorescein and fluorescein isothiocyanate conjugates

It is shown that fluorescein is susceptible to bleaching in the presence of organic peroxides, hydroperoxides and oxyradicals. The effectiveness with which enzymes, which can inhibit oxidation processes, retard the photobleaching of fluorescein isothiocyanate conjugates indicates that dye/protein oxidation products are involved in the mechanism of dye fading.

Measurements of peroxides in cloudwater and rain

Measurements of total peroxide content are reported for 190 cloud water samples from nonsupercooled stratiform clouds, and for 54 rain samples, collected at several nonurban sites in the eastern United States. Observed aqueous peroxide concentrations ranged from less than 0.1 μM to over 100 μM, with rain samples, precipitating cloudwater samples, and nonprecipitating cloudwater samples all exhibiting median values of less than 10 μM and similar concentration distributions. Specific analyses for H2O2 on 48 of the samples showed that in the majority of samples tested, H2O2 was the sole contributor to the total peroxide concentration, but in some samples, substantial signal was observed after selective destruction of H2O2, possibly indicating the presence of organic peroxides. Calculation of the total potential partial pressure of H2O2 for the samples collected in nonprecipitating clouds, using the measured aqueous concentrations and cloud liquid water content values, indicates a median potential partial pressure of H2O2 of 0.1 ppbv, and a maximum value of approximately 1 ppbv, Gaseous SO2 and aqueous peroxide were rarely simultaneously present in substantial concentrations; generally one reactant was present in great excess over the other, consistent with the occurrence of the aqueous phase reaction of peroxide with S(IV) in which one or the other species is the limiting reagent. Evaluation of the rates of S(IV) oxidation by peroxide and ozone, under conditions representative of the clouds sampled in this study, indicates that the former reaction, but not the latter, can produce substantial acidification in such clouds.

Hydrophosphorylation of polyallene

A study was made of hydrophosphorylation of polyallene in the presence of organic peroxides. Hypophosphorous acid and its salts, alkylphophonous acids and dialkylphosphites were used as hydrophosphorylating agents. Phosphono-alkylated polymers containing up to 11% phosphorous, insoluble in organic solvents and not supporting combustion were obtained. It was found that hydrophosphorylation of polyallene reduces the crystallinity of polymers and increases their heat stability. Polymer-analogous conversions of polyallenephosphonous acid were carried out.

Reaction of Maleic Anhydride with Unsaturated Fatty Acids in the Presence of Organic Peroxides

Reaction of maleic anhydride with linoleic and oleic acids in the presence of organic peroxides was investigated. The peroxides used were benzoyl peroxide (BPO), di-tert-butyl peroxide (DtBPO), and dicumyl peroxide (DCPO). The maleinization reaction was accelerated by the presence of organic peroxides, and was carried out at a temperature that the peroxides decompose (about 130°C). The orders of the activities of the reaction were as follows : (i) On the peroxides DCPO ≥ DtBPO >> BPO (ii) On the maleic anhydride and its related compounds maleic anhydride >> maleic acid > dimethyl fumarate ≥ fumaric acid > dimethyl maleate (iii) On fatty acids linoleic acid > oleic acidIn the case of the reaction of linoleic acid with maleic anhydride, a product of resinous powder (mp ; about 130°C) was obtained. On the structure of maleinized product it was presumed that the main product was dimer, crosslinked by maleic anhydride, of maleic anhydride added to linoleic acid (III), and that the by-product was ketonic compounds derived by decarboxylation from two acid anhydride groups in the main product (III).(III) From the results obtained, a biradical addition reaction mechanism was postulated.

Homolytic mechanisms of aromatic rearrangements. Part I. The rearrangement of N-chloroacetanilide

The kinetics and products of the rearrangement of N-chloroacetanilide, catalysed by light and by benzoyl peroxide in carbon tetrachloride, catalysed by t-butyl peroxide in chlorobenzene, and in hot glacial acetic acid, and the products of the rearrangement catalysed by hydrogen chloride in acetic acid and in carbon tetrachloride, have been investigated. The reactions in the presence of light or free-radical initiators, and in acetic acid, are autocatalysed, partly owing to the formation of hydrogen chloride in a side-reaction. The kinetics, and the ratios of isomeric chloroacetanilides formed under various conditions, are consistent with an initial homolytic reaction, which is followed by a faster, heterolytic reaction, catalysed by hydrogen chloride. In the presence of organic peroxides, a third mechanism, involving nuclear chlorination of acetanilide by t-butyl hypochlorite or benzoyl hypochlorite, is also an important contributor to the total reaction.

THE ADDITION OF CARBOXYLIC ACIDS TO ACETYLENIC COMPOUNDS

The free radical induced addition of acetic acid and its derivatives to olefins has been reported recently. As an extension of this reaction, the addition of acetic acid to acetylenic compounds was investigated.Adipic acid was found to be the major product of the reaction of excess acetic acid and acetylene at 110–120 °C under pressure in the presence of organic peroxides. A second oily acidic product with a molecular weight of about 300, not yet identified, was found to the extent of about 2 parts by weight to every 3 parts of adipic acid.Octen-3-oic acid and its anhydride were synthesized from hexyne-1 and excess acetic acid in the presence of organic peroxides. Acetic anhydride was substituted for acetic acid, with the net advantage that acetylene was more soluble in the solvent. The general scope of the reaction was expanded to include other transfer agents, such as acetone, formic acid, and propionic acid.

New Procedure for Determination of Oxygenated Water in the Presence of Organic Peroxides

New Procedure for Determination of Oxygenated Water in the Presence of Organic Peroxides

The Action of Sulphuryl Chloride on Wool

Sulphuryl chloride is known to make wool unshrinkable by canning disulphide bond breakdown in the surface scale structxire of the fibres. It has now been found that the aotion of sulphuryl chloride on commercial flannel is seriously impaired when residual oil and soap are removed by extraction with ether and alcohol. High reactivity with sulphuryl chloride can, however, be restored if sodium oleate or oleic acid, but not stearic acid, is added to the purified fabric from solution in alcohol. Within the limits of the experimental error, all the oleic acid added in this way can be removed by extraction with carbon tetrachloride without causing any serious fall in reactivity. It is obvious, therefore, that oleic acid does not itself promote the reaction between sulphuryl chloride and wool, but is the source of some substance, present in small quantity, which is the active compound. The latter can be isolated by extracting the fabric with alcohol, after first removing the oleic acid with carbon tetrachloride. When the alcohol extract is applied to a purified fabric, high reactivity with sulphuryl chloride is again observed.These observations suggest that the active compound in oleic acid is an organic peroxide, and con. firmation has been found in the fact that benzoyl peroxide has the same effect as oleic acid when applied to purified wool from alcoholic solution. By analogy with the chlorination of alkyl groups with sulphuryl chloride in presence of organic peroxides, it is believed that the latter assist the reaction between sulphuryl chloride and the disulphide bonds of wool by initiating reaction chains involving free chlorine atoms. If, therefore, peroxides are deliberately introduced into wool before treatment with sulphuryl chloride, the rate of reaction should be high enough to make continuous processing possible.