Absence Of CuCl Research Articles

One Reaction: Two Types of Mechanism-SARA-ATRP and SET-LRP-for MMA Polymerization in the Presence of PVC.

This study presents for the first time the polymerization of methyl methacrylate (MMA) in the presence of poly(vinyl chloride) (PVC) that takes place by both SARA-ATRP and SET-LRP mechanisms. The two types of polymerizations that occur in the system are PMMA grafting to the PVC backbone and the formation of a new PMMA polymer, both occurring in the presence of a Cu0wire. The polymerizations were controlled as confirmed by the molecular weight evolution, polymerization kinetics, and variations in the dispersity value. The MMA polymerization in the presence of PVC at 60 and 70 °C leads to the formation of two polymer species characterized by an increase in the molecular weight with the conversion and a narrowing of the dispersity value with the reaction progress. To increase the degree of control over the polymerization, the same reaction was performed at room temperature, which allowed us to highlight the presence of the SARA-ATRP and SET-LRP mechanisms via subsequent polymer chain extensions. The results demonstrated that PMMA grafting on PVC polymers follows a SARA-ATRP mechanism, while the formation of a PMMA homopolymer entails a SET-LRP process. The influence of solvent nature on the polymerization reaction was studied by performing the grafting of N-isopropylacrylamide (NIPAM) onto the surface of PVC particles in aqueous media in the presence and in the absence of CuCl2. The polymerization reactions and the obtained materials were studied by gel permeation chromatography (GPC), 1H NMR, DMA, scanning electron microscopy (SEM), and atomic force microscopy (AFM).

EDTA, thymidine, and Cu2+ ion complexes from mass spectrometry data

Electrospray ionization mass spectrometry is used to study thymidine solutions in the presence of copper ions and EDTA. The results show formation of thymidine–EDTA complexes in the absence of CuCl2, and the existence of thymidine–EDTA–CuCl2 complexes in a CuCl2 and EDTA containing thymidine solution. The stoichiometry of the complexes is determined.

Methanobactin from Methylocystis sp. strain SB2 affects gene expression and methane monooxygenase activity in Methylosinus trichosporium OB3b.

Methanotrophs can express a cytoplasmic (soluble) methane monooxygenase (sMMO) or membrane-bound (particulate) methane monooxygenase (pMMO). Expression of these MMOs is strongly regulated by the availability of copper. Many methanotrophs have been found to synthesize a novel compound, methanobactin (Mb), that is responsible for the uptake of copper, and methanobactin produced by Methylosinus trichosporium OB3b plays a key role in controlling expression of MMO genes in this strain. As all known forms of methanobactin are structurally similar, it was hypothesized that methanobactin from one methanotroph may alter gene expression in another. When Methylosinus trichosporium OB3b was grown in the presence of 1 μM CuCl2, expression of mmoX, encoding a subunit of the hydroxylase component of sMMO, was very low. mmoX expression increased, however, when methanobactin from Methylocystis sp. strain SB2 (SB2-Mb) was added, as did whole-cell sMMO activity, but there was no significant change in the amount of copper associated with M. trichosporium OB3b. If M. trichosporium OB3b was grown in the absence of CuCl2, the mmoX expression level was high but decreased by several orders of magnitude if copper prebound to SB2-Mb (Cu-SB2-Mb) was added, and biomass-associated copper was increased. Exposure of Methylosinus trichosporium OB3b to SB2-Mb had no effect on expression of mbnA, encoding the polypeptide precursor of methanobactin in either the presence or absence of CuCl2. mbnA expression, however, was reduced when Cu-SB2-Mb was added in both the absence and presence of CuCl2. These data suggest that methanobactin acts as a general signaling molecule in methanotrophs and that methanobactin "piracy" may be commonplace.

Zirconium-mediated multicomponent reactions of 1,3-butadiynes with ylidenemalononitriles to form functionalized 1,8-naphthyridine and cyclopenta[b]pyridine derivatives.

Zirconocene-mediated multicomponent reactions of 1,3-butadiynes with ylidenemalononitriles in the absence or presence of CuCl have been developed. In the absence of CuCl, 1,3-butadiyne couples with three molecules of ylidenemalononitriles to yield azazirconacycles bearing a hexahydro-1,8-naphthyridine skeleton with high stereoselectivity. In the presence of CuCl, cyclopenta[b]pyridine or cyclopenta[b]quinolin-1-one derivatives are obtained via transmetalation of Zr-C bond to Cu-C bond as the key reaction step. These domino-type reactions proceed with high chemo-, regio- and/or stereoselectivities, and allowing the formation of multiple C-N and C-C bonds in a single operation.

Characterization of oxidation products from 1-palmitoyl-2-linoleoyl-sn-glycerophosphatidylcholine in aqueous solutions and their reactions with cysteine, histidine and lysine residues

This report focuses on studies of lipid peroxidation products reactivity towards the side chains of cysteine, histidine, and lysine residues in structurally unordered peptides. Thus we have analyzed linoleic acid peroxidation products (LaPP) obtained by incubating 1-palmitoyl-2-linoleoyl-sn-glycerophosphatidylcholine (PLPC) overnight with or without H2O2 in the presence or absence of CuCl. In total, 55 different LaPP were identified with 26 containing reactive carbonyl groups. The strongest oxidation conditions (H2O2 and Cu(I), i.e. a Fenton-like reagent) yielded 51 LaPP, whereas air oxidation produced only 12 LaPP. Independent of the oxidation conditions, around half of all LaPP were short-chain (oxidative cleavage) and the others long-chain (oxygen addition) PLPC oxidation products. The stronger oxidation conditions increased the number of LaPP, but also oxidized the added peptide Ac-PAAPAAPAPAEXTPV-OH (X=Cys, His or Lys) very quickly, especially under Fenton conditions. Thus, PLPC was oxidized by milder conditions (air or Cu(I)), incubated with the peptide and the peptide modifications were then analyzed by nano-RPC-ESI-Orbitrap-MS. Ten LaPP-derived peptide modifications were identified at lysine, whereas nine products were identified for cysteine and only three for histidine. Three high molecular weight LaPP still esterified to the GPC backbone were detected on Lys-containing peptide. Furthermore, three LaPP-derived mass shifts were obtained at cysteine, which have not previously been reported.

Synergized Action of CuCl on Recycled Cigarette Butts as Corrosion Inhibitor for N80 Steel at 90 °C in 15% HCl

One of effective ways to reduce pollution from cigarette butts is introduced by recycling the cigarette butts. Inhibitor from recycled cigarette butts shows good inhibition properties, but we do not know whether CuCl can help to improve the inhibition efficiency. So, in this study, the impact of CuCl on recycled cigarette butts as corrosion inhibitor for N80 steel at 90 °C in 15% HCl is studied by weight loss, electrochemical noise, polarization, impedance, and X-ray photoelectron spectroscopy. All the results show that the inhibition efficiency of water extracts from cigarette butts in the presence of CuCl is higher than in absence of CuCl, and it can reach 95.3% when 9% water extracts with copper added is used. The X-ray photoelectron spectroscopy results indicate that the N80 steel specimen surface is undamaged and covered with a protective coat formed by copper-added water extracts from cigarette butts. CuCl has synergizing action on recycled cigarette butts as a corrosion inhibitor for N80 steel at 90 °C in 15% HCl.

Highly efficient solvent-free synthesis of quinazolin-4(3 H)-ones and 2,3-dihydroquinazolin-4(1 H)-ones using tetrabutylammonium bromide as novel ionic liquid catalyst

A simple and efficient procedure for the synthesis of 2-arylquinazolin-4(3 H)-ones has been developed through cyclocondensation of 2-aminobenzamide with aromatic aldehydes using tetrabutylammonium bromide (TBAB) as novel neutral ionic liquid catalyst in the presence of copper (II) chloride (CuCl 2) as oxidizing agent under solvent-free conditions at 100 °C. In the absence of CuCl 2 and under a nitrogen atmosphere, the unoxidized intermediates, 2-aryl-2,3-dihydroquinazolin-4(1 H)-ones, were isolated. Treatment of these intermediates with CuCl 2 in TBAB media gave the oxidized products 2-arylquinazolin-4(3 H)-ones. On the other hand, cyclocondensation of 2-aminobenzamide with aromatic aldehydes in TBAB under microwave irradiation directly gave 2-arylquinazolin-4(3 H)-ones.

Mechanism of Redox-mediated Guanine Nucleotide Exchange on Redox-active Rho GTPases

Rho GTPases regulate multiple cellular processes including actin cytoskeletal rearrangements, transcriptional regulation, and oxidant production. The studies described herein demonstrate that small molecule redox agents, in addition to protein regulatory factors, can regulate the activity of redox-active Rho GTPases. A novel (GXXXXGK(S/T)C) motif, conserved in a number of Rho GTPases, appears critical for redox-mediated guanine nucleotide dissociation in vitro. A detailed molecular mechanism for redox regulation of GXXXXGK(S/T)C motif-containing Rho GTPases is proposed.

Palladium catalyzed oxidation of monoterpenes: NMR study of palladium(II)–monoterpene interactions

Reactions of the monoterpenes β-pinene, limonene and myrcene with Pd(II) complexes in acetic acid solutions were studied by 1H NMR spectroscopy. Various π-allyl palladium complexes were detected in situ and their interaction with CuCl 2 has been investigated. The results clarify the mechanism of allylic oxidation of these substrates mediated by Pd(II)/Cu(II)-based catalytic systems. Originally introduced to regenerate reduced palladium species, CuCl 2 has been shown to play an important role in the formation and/or decomposition of key reaction intermediates – π-allyl palladium complexes. β-Pinene and myrcene readily react with Pd(OAc) 2 giving corresponding π-allyls, with two complexes acyclic and cyclic being formed from myrcene. On the other hand, the formation of π-allyl complexes from limonene occurs at a significant rate only in the presence of CuCl 2. NMR observations, including selective paramagnetic enhancement of spin-lattice relaxation, indicate that π-allyl palladium intermediates specifically interact with Cu(II) ions in the reaction solutions. Such interaction probably involves Cu(II) bonding to Pd(II) via bridging ligands, and seems to be responsible for the accelerative effect of CuCl 2 in the palladium catalyzed oxidation of the monoterpenes. Indeed, most of these reactions do not occur at all in the absence of CuCl 2.

Asymmetric Hydroesterification of Styrene Using Catalysts with Planar‐Chiral Ferrocene Oxazoline Ligands.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Asymmetric hydroesterification of styrene using catalysts with planar-chiral ferrocene oxazoline ligands

Chiral P, N-ferrocene ligands, 1-diphenylphosphino-1′-[( S)-4-isopropyl-2.5-oxazolinyl]-2′-( S p )-(trimethylsilyl)-ferrocene and its diastereomer, and 1-diphenylphosphino-1′-[( S)-4-isopropyl-2.5-oxazolinyl]-2′( S p )-(diphenylphosphino)-ferrocene and its diastereomer were used in the palladium-catalyzed asymmetric hydroesterification of styrene. The role of these ligands, which contain central, axial, and planar chirality, on the stereochemical outcome was investigated. A significant effect of using CuCl 2 as a co-catalyst on the reaction was observed. Excellent regioselectivity (b/n >99:1) with low ee (28%) was obtained in the presence of CuCl 2; moderate enantioselectivity (64% ee) but low regioselectivity (b/n, 40/60) was obtained in the absence of CuCl 2.

Electrical conductivity and thermal properties of poly(m‐aminophenyl acetic acid) and its copolymers with aniline

AbstractPoly(m‐aminophenyl acetic acid) was synthesized under different conditions from the respective monomer, using ammonium persulfate as oxidizing agent in both the presence and the absence of CuCl2 in HCl(aq). Moreover, the copolymers between aniline and m‐aminophenyl acetic acid were prepared at several feed mol ratios (f1) of aniline. Copper was introduced by the Batch method in the homo‐ and copolymers of different compositions. The polymers were characterized by FTIR and UV‐vis spectroscopy, elemental analysis, thermal analysis, and electrical conductivity. The thermal stability and the content of copper increased as the content of aniline was increased in the copolymers. Moreover, the copolymers showed a high thermal stability; at 400°C a weight loss < 10% was observed. The electrical conductivity was increased with a higher content of aniline in the copolymers, achieving semiconduction values. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1484–1492, 2003

Reactivity of the Carbyne Complexes [W2(μ-COR)(η5-C5H5)2(CO)2(μ-Ph2PCH2PPh2)]+(R = H, Me) toward Diazomethane

Reaction of [W2(μ-COH)Cp2(CO)2(μ-dppm)]BF4 (Cp = η5-C5H5; dppm = Ph2PCH2PPh2) with CH2N2 in the presence of CuCl at −75 °C leads to the methoxycarbyne cluster [CuW2Cl(μ3-COMe)Cp2(CO)2(μ-dppm)]BF4. Copper(I) chloride can be cleanly removed from the latter upon addition of PPh3, thus giving the methoxycarbyne complex [W2(μ-COMe)Cp2(CO)2(μ-dppm)]BF4. In the absence of CuCl, either the hydroxy or the methoxycarbyne ditungsten cations react with CH2N2 to give a mixture of the μ-methylene, μ-alkenyl compound [W2(μ-CH2){μ-η1:η2-C(OMe)CH2}Cp2(CO)2(μ-dppm)]BF4, which has been characterized through an X-ray study, and the μ-alkyne, μ-alkenyl species [W2{μ-η1:η2-C(OMe)CH}{μ-η1:η2-C(OMe)CH2}Cp2(CO)(μ-dppm)]BF4, the latter being the result of the addition of four molecules of CH2N2 to the starting hydroxycarbyne compound. The influence of experimental conditions on the above reactions has been analyzed through separate experiments. For example, the use of tetrahydrofuran as solvent almost suppresses the formation of t...

Phosphinidene reactivity toward unsaturated phosphorus heterocycles

Abstract The transient electrophilic phosphinidene complex PhPW(CO)5 reacts in the presence of CuCl at room temperature with phospholene 2 and phospholes 4a–c to give the corresponding W(CO)5 complexed products 3 and 5a–c. The intermediate phosphoranylidene phosphine complexes, formed, from the addition of PhPW(CO)5 to the phosphorus atom of the substrates, are characterized by NMR spectroscopy and by a single crystal X-ray structure determination for the one generated from phospholene 2. This intermediate 8 is a CuCl-complexed dimer, which speculatively results from dissociating the phosphole–CuCl tetramer on insertion of PhPW(CO)5 into the P–Cu bonds. Reacting PhPW(CO)5 with phospholene 2 at 110°C in the absence of CuCl gives besides the W(CO)5-complexed phospholene 3 also a bisphospholene–W(CO)4 complex 13. The formation of 13 is attributed to a ligand exchange reaction in the intermediate phosphinidene–phospholene adduct.

Metal toxicity on the dechlorination of monochlorophenols in fresh and acclimated anaerobic sediment slurries

The biotransformation of 2- and 3-chlorophenol(CP) was examined in anaerobic fresh and acclimated sediments in the presence and absence of CuCl2, CdCl2 and K2Cr2O7 ranging from 10 to 200 mg/l. Differing inhibitory effects of specific metals were observed on dechlorination of CPs in sediment slurries. In case of fresh unacclimated slurry, addition of 20 mgCu/l resulted in no appreciable inhibition of dechlorination for tested CPs. In contrast, 20 mg/l of Cd and Cr moderately affected lag periods prior to dechlorination. In this case, Cd was more inhibitory than either Cu or Cr (Cd > Cr ≥ Cu), which illustrated nearly similar effect. In case of acclimated slurry, the dechlorination activity of 2- and 3-CP was inhibited in the presence of 20 mg/l of three tested metals. Metals amended to 2- and 3-CP acclimated sediments exhibited inhibition degree in the order of Cd > Cu > Cr, which are different patterns compare to fresh slurry.

Metal toxicity on the dechlorination of monochlorophenols in fresh and acclimated anaerobic sediment slurries

The biotransformation of 2- and 3-chlorophenol(CP) was examined in anaerobic fresh and acclimated sediments in the presence and absence of CuCl2, CdCl2 and K2Cr2O7 ranging from 10 to 200 mg/l. Differing inhibitory effects of specific metals were observed on dechlorination of CPs in sediment slurries. In case of fresh unacclimated slurry, addition of 20 mgCu/l resulted in no appreciable inhibition of dechlorination for tested CPs. In contrast, 20 mg/l of Cd and Cr moderately affected lag periods prior to dechlorination. In this case, Cd was more inhibitory than either Cu or Cr (Cd > Cr ≥ Cu), which illustrated nearly similar effect.In case of acclimated slurry, the dechlorination activity of 2- and 3-CP was inhibited in the presence of 20 mg/l of three tested metals. Metals amended to 2- and 3-CP acclimated sediments exhibited inhibition degree in the order of Cd > Cu > Cr, which are different patterns compare to fresh slurry.

A new method for monitoring dediazoniation reactions: Simultaneous monitoring of concentration and rates of product formation and loss of starting material for the dediazoniation ofp-methylbenzenediazonium tetrafluoroborate

We have examined the kinetics and mechanism of the dediazoniation reaction of p-methylbenzenediazonium tetrafluoroborate in the presence and absence of CuCl2 using a methodology developed by us that allows, simultaneously, and within the same experiment to identify, to quantify, and to obtain the rate constants for the formation of all dediazoniation products, and, indirectly, the rate constant for the diazonium salt decomposition. The methodology developed combines the use of coupling reactions, to form a stable azo dye, followed by analysis by HPLC. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 31–39, 1998.

Oxidation of olefins by palladium(II). Part XIV . Product distribution and kinetics of the oxidation of ethene by PdCl 3 (pyridine) − in aqueous solution in the presence and absence of CuCl 2: a modified Wacker catalyst with altered reactivity

In the absence of CuCl 2, ethene was oxidized to ethanal by PdCl 3 (pyridine) − in aqueous solution by the rate expression: − d[C 2H 4] dt = k′K′ [PdCl 3(Py) −][C 2H 4] [H +][Cl −] 2 where K′ is the equilibrium constant for π-complex formation between ethene and PdCl 3(Py) − (Py = pyridine). This rate expression is of the same form as that previously found for the oxidation of ethene by PdCl 2− 4 in aqueous solution (Wacker reaction). The value of K′ for PdCl 3(Py) − was found to be 20.3 which is close to the value of 17.4 previously measured for π-complex formation between ethene and PdCl 2− 4. However, the value of k for PdCl 2− 4 was 750 times the value of k′ for PdCl 3(Py) −. This result suggests that the hydroxypalladation adduct from PdCl 3(Py) − is much more stable towards decomposition to ethanal than the corresponding one from PdCl 2− 4. A direct result of this higher stability is the expectation that the adduct from PdCl 3(Py) − should be more readily intercepted by CuCl 2 to produce 2-chloroethanol. At chloride concentrations as low as 0.2 M and [CuCl 2] = 4 M, the product was almost 50% 2-chloroethanol. At [CuCl 2] = 8 M, the product was 98% 2-chloroethanol. With PdCl 2− 4, a chloride concentration of 3 M is required before an appreciable amounts of 2-chloroethanol are produced at any cupric chloride concentration. For the reaction of ethene with PdCl 2− 4, these results are consistent with a mechanism involving cis addition at low [Cl −] and trans addition at high [Cl −]. The pathway for ethanal formation may be different with PdCl 3(Py) − than it is with PdCl 2− 4.

Elevation of [ 3H]cimetidine binding by CuCl 2 in brain membranes of rats

Influences of dithiothreitol (DTT), p-chloromercuriphenyl sulfonate (PCMPS) and ascorbate on CuCl 2-induced elevation of [ 3H]cimetidine binding were investigated in brain membranes of rats. CuCl 2 (10–500 μM) elevated specific [ 3H]cimetidine binding in a concentration-dependent manner. There were two types of [ 3H]cimetidine binding in the presence of 50 μM CuCl 2: high affinity binding with K d = 1.97 nM and low affinity with K d = 21.6 nM. PCMPS (10 and 100 μM) reduced the binding in both media with and without CuCl 2. DTT (1–30 μM) or ascorbate (0.1 and 1.0 mM) markedly elevated the binding in the presence of CuCl 2 but showed no effect and ascorbate rather inhibited the binding in the absence of CuCl 2. DTT (0.1 mM) diminished the binding in the presence and absence of CuCl 2. CuCl 2 (50 μM) significantly ( P < 0.01) increased the IC 50 of histamine for [ 3H]cimetidine binding and the effect was greater than that from 100 μM GTP. It is suggested that sulfhydryl groups sensitive to PCMPS could interact with Cu 2+ and thus be involved in an elevation of cimetidine binding. Cu 2+ seems to regulate affinity of agonist binding for cimetidine binding sites presumably by acting on cimetidine binding sites and/or GTP binding regulatory proteins.

The regulatory mechanism in histamine H2 receptor binding of the rat brain : Effects of Cu2+, dithiothreitol and ascor-bate

To identify the regulatory mechanism of histamine H2 receptors in the CNS, influences of Cu2+, dithiothreitol (DTT) and ascor-bate on [3H]Cimetidine binding to crude synaptic membranes were investigated in the male Wistar rat brain. Fifty μM CuCl2 increased 3-fold specific [3H]Cimetidine binding compared to the control. In the presence of 50 μM CuCl2, Scatchard plots showed an upward curve, which was divided into two types of binding sites : high affinity (KD=1.97 nM) and low affinity (KD=21.6 nM). The inhibitory potency (IC50) of metiamide on the binding was not affected by 50 μM CuCl2 (control, 0.16 μM ; CuCl2, 0.14 μM), although the inhibitory effect of mepyramine up to 0.1 mM was not observed in the presence of CuCl2 compared to that (IC50=0.1 mM) in the control. In the presence of 50 μM CuCl2, 0.1 - 30 μM DTT and 10 μM - 10 mM ascorbate increased the binding in a concentration-dependent manner, but both drugs showed no effect in the absence of CuCl2. These results suggest that [3H]Cimetidine binding sites indicate histamine H2 receptors that are specifically increased by Cu2+ and that dithiothreitol and ascorbate enhance the increasing effect of Cu2+. In contrast, influence of Cu2+ on GTP regulatory protein is also suggested from a finding that 50 μM CuCl2 reduced the affinity of histamine to [ 3H]Cimetidine binding sites.