Presence Of KI Research Articles

Iodination of phenols in water using easy to handle amine-iodine complexes

The reaction between iodo and N-methyl-piperazine or thiomorpholine in water, in the presence of KI, led to the formation of stable and easy to handle amine-iodine complexes, as the complex morpholine-iodo previously reported in the literature. However, the complex obtained using N,N-tetrametylethylenediamine proved less stable, while no complex was formed when piperidine was used as base. These results show that the presence of a second heteroatom in the structure of amines is of fundamental importance for the formation and stability of these complexes. In this work we describe, for the first time, the use of complexes morpholine-iodo, N-methyl-piperazine-iodo and thiomorpholine-iodo as iodinating reagents of several substituted phenols, leading to iodinated products in good to excellent yields.

Novel Application of an Electrooxidative Method for the Formation of a Tetrahydrofuran Ring from 5-Hydroxy-2-pentanone Phenylhydrazone

Various ketone phenylhydrazones that possess a hydroxy group on the parent ketone moiety were subjected to electrooxidation in methanol in the presence of KI and NaOMe. In the case of 4-hydroxy-2-butanone phenylhydrazone, the nucleophilic attack of the azomethine carbon by a methoxide ion affording the corresponding methoxy(phenylazo)alcohol was dominant. Interestingly, however, in the case of 5-hydroxy-2-pentanone phenylhydrazone, similar reaction conditions favored the intramolecular cyclization to afford a (phenylazo)tetrahydrofuran derivative.

Anodic Stripping Voltammetric Detection of Arsenic(III) at Gold Nanoparticle‐Modified Glassy Carbon Electrodes Prepared by Electrodeposition in the Presence of Various Additives

AbstractThe simple, fast and highly sensitive anodic stripping voltammetric detection of As(III) at a gold (Au) nanoparticle‐modified glassy carbon (GC) (nano‐Au/GC) electrode in HCl solution was extensively studied. The Au nanoparticles were electrodeposited onto GC electrode using chronocoulometric technique via a potential step from 1.1 to 0 V vs. Ag|AgCl|NaCl (sat.) in 0.5 M H2SO4 containing Na[AuCl4] in the presence of KI, KBr, Na2S and cysteine additives. Surfaces of the resulting nano‐Au/GC electrodes were characterized with cyclic voltammetry. The performances of the nano‐Au/GC electrodes, which were prepared using different concentrations of Na[AuCl4] (0.05–0.5 mM) and KI additive (0.01–1.0 mM) at various deposition times (10–30 s), for the voltammetric detection of As(III) were examined. After the optimization, a high sensitivity of 0.32 mA cm−2 μM−1 and detection limit of 0.024 μM (1.8 ppb) were obtained using linear sweep voltammetry.

Adsorption and Corrosion Inhibition Effect of 1,1′-Thiocarbonyldiimidazole on Mild Steel in H 2SO 4 Solution and Synergistic Effect of Iodide Ion

The inhibition effect of 1,1′-thiocarbonyldiimidazole (TCDI) on the corrosion behaviors of mild steel (MS) in 0.5 mol·L −1 H 2SO 4 solution was studied with the help of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and linear polarization resistance (LPR) techniques. The effect of immersion time on the inhibition effect of TCDI was also investigated over 72 h. For the long-term tests, hydrogen evolution with immersion time ( V H 2– t) was measured in addition to the three techniques already mentioned. The thermodynamic parameters, such as adsorption equilibrium constant ( K ads) and adsorption free energy (Δ G ads) values, were calculated and discussed. To clarify inhibition mechanism, the synergistic effect of iodide ion was also investigated. The potential of zero charge (PZC) of the MS was studied by electrochemical impedance spectroscopy method, and a mechanism of adsorption process was proposed. It was demonstrated that inhibition efficiency increased with the increase in TCDI concentration and synergistically increased in the presence of KI. The inhibition efficiency was discussed in terms of adsorption of inhibitor molecules on the metal surface and protective film formation.

The influence of halide-mediated oxidation on algae-born adhesives.

Adhesive materials extracted from the brown algae Fucus Serratus were studied. These adhesives are composed of cross-linked alginate and polyphenols oxidized in the presence of KI or KBr. All formulations were capable of adhering to a variety of surfaces, however the adhesion properties were influenced by the halide used. SAXS and TEM experiments revealed that oxidized polyphenols self-assemble into chain-like objects, irrespective of the oxidation conditions. Yet, slight differences in the aggregate size were detected. QCM-D results showed that the kinetics of the oxidation was faster with iodide than with bromide. Moreover, oxidation with iodide generates stiffer networks, suggesting that the interaction between the alginate and the polyphenol could be the cause of the reduced adhesion.

Corrosion inhibition and adsorption behavior of methionine on mild steel in sulfuric acid and synergistic effect of iodide ion

The corrosion inhibition of mild steel in sulfuric acid by methionine (MTI) was investigated using electrochemical techniques. The effect of KI additives on corrosion inhibition efficiency was also studied. The results reveal that MTI inhibited the corrosion reaction by adsorption onto the metal/solution interface. Inhibition efficiency increased with MTI concentration and synergistically increased in the presence of KI, with an optimum [KI]/[MTI] ratio of 5/5, due to stabilization of adsorbed MTI cations as revealed by AFM surface morphological images. Potentiodynamic polarization data suggest that the compound functioned via a mixed-inhibition mechanism. This observation was further corroborated by the fit of the experimental adsorption data to the Temkin and Langmuir isotherms. The inhibition mechanism has been discussed vis-à-vis the presence of both nitrogen and sulfur atoms in the MTI molecule.

Quenching-enhanced fluorescence titration protocol for accurate determination of free energy of membrane binding

Quenching-enhanced fluorescence titration protocol for accurate determination of free energy of membrane binding

Direct Iodination of Aromatic Compounds with Polyvinylpyrrolidone Supported Hydrogen Peroxide (PVP-H2O2) and Potassium Iodide or Molecular Iodine

Hydrogen peroxide was supported on polyvinylpyrrolidone to afford a stable and mild oxidizing reagent. Activated aromatic compounds were reacted with PVP-H2O2 in the presence of KI or I2 and a catalytic amount of H3PW12O40 in refluxing CH2Cl2 to afford the corresponding iodinated arenes.

Adsorption behavior and synergistic mechanism of a cationic inhibitor and KI on the galvanic electrode

The synergistic effect between KI and imidazoline derivative as a cationic inhibitor for inhibiting galvanic corrosion has been investigated by using electrochemical methods, atomic force microscopy and Fourier transform infrared (FTIR) spectroscopy. A galvanic electrode was prepared by coupling N80 carbon steel and S31803 stainless steel, and all experiments were performed in NaCl solution in the presence or absence of imidazoline derivative (MAD) and KI. Zero charge potential experiments reveal carbon steel and stainless steel carry positive and negative excess charges in NaCl solution, respectively, and stainless steel carries negative excess charge in NaCl solution with KI. Polarization curves and galvanic current measurements suggest that, for the galvanic corrosion, both MAD and KI are mainly cathodic type inhibitors, and a synergistic effect exists between KI and MAD. FTIR and AFM were used to analyze the inhibitor film formed on the surface of the electrodes. Results show that in the presence of KI, compared with that in the absence of KI, the inhibitor film on the anode of galvanic electrodes (GE) is more compact, and the adsorbability of the inhibitor on the surface of carbon steel is strengthened. A suitable mechanism of corrosion inhibition is proposed based on the results obtained from electrochemical measurements, AFM and FTIR. It is found that the anion I − can change the distribution of excess charge on the surface of galvanic electrode, thus helps the inhibitor to adsorb on both the cathodic area and the anodic area.

Interaction of polydiallyldimethylammonium salts with iodine

AbstractThe interaction between polydiallyldimethylammonium chloride (PDADMAC) and KI or KBr, followed by changes in conformation of macromolecules, coil compaction, and counterion exchange, was detected by means of turbidimetry and viscometry. In aqueous solutions at presence of KI, PDADMAC rapidly binds iodine by the formation of polymer–iodine complexes PDADMA I− Im (m ≤ 4). Spectrophotometric investigations of the interaction in water without KI prove the formation of complexes of polyquaternary ammonium chloride or bromide with iodine only via iodide. These ions can be generated in the polymer‐catalyzed hydrolysis reaction of iodine. By inducing hydrolysis of iodine and binding the eventually formed iodide, PDADMAC acts as an iodine acceptor with self‐strengthening capacity. For the sorption of gaseous iodine, the possibility of direct interaction of its dipoles with the charged groups of the polyelectrolyte is also reasoned. Polydiallyldimethylammonium halides were used to modify activated carbon and employed in a nuclear power station for treatment of outlet gases containing radioactive iodine. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2710–2716, 2006

Synthesis of Oligophenylene-Substituted Calix[4]crown-4s and Their Silver(I) Ion-Induced Nanocones Formation

A novel series of oligophenylene OPP(n)-substituted calix[4]crown-4s bearing up to three phenylene units, 1a-d, has been efficiently synthesized by means of either microwave-assisted or silver(I) ion-assisted Pd-catalyzed Suzuki cross-coupling of tetraiodocalix[4]crown-4 and the corresponding oligophenylboronic acids. Complexation of OPP(n)-substituted calix[4]crown-4s with silver (I) ion was substantiated by 1H NMR spectroscopic and high-resolution ESI- or MALDI-TOF- MS studies. The weak binding affinities of OPP(n)-substituted calix[4]crown-4s for silver (I) ion, which were estimated from 1H NMR titrations with binding association in the range of 30-90 M(-1), allows reversible disassembling in the presence of KI at ambient temperature. Remarkably, the single-crystal X-ray structures of OPP(n)-calix[4]crown-4.Ag+ complexes indicate the atypical silver (I) ion-crown ether binding mode resulting in the formation of rigid nanocones with volume created up to approximately 1500 A(3). Our results suggested that despite the weak binding affinity of crown ether ligands for silver (I) ion, this weak interaction is still be useful as a tool to construct supramolecular architectures.

Scanning the Membrane-bound Conformation of Helix 1 in the Colicin E1 Channel Domain by Site-directed Fluorescence Labeling

Helix 1 of the membrane-associated closed state of the colicin E1 channel domain was studied by site-directed fluorescence labeling where bimane was covalently attached to a single cysteine residue in each mutant protein. A number of fluorescence properties of the tethered bimane fluorophore were measured in the membrane-bound state of the channel domain, including fluorescence emission maximum, fluorescence quantum yield, fluorescence anisotropy, membrane bilayer penetration depth, surface accessibility, and apparent polarity. The data show that helix 1 is an amphipathic alpha-helix that is situated parallel to the membrane surface. A least squares fit of the various data sets to a harmonic function indicated that the periodicity and angular frequency for helix 1 are typical for an amphipathic alpha-helix (3.7 +/- 0.1 residues per turn and 97 +/- 3.0 degrees, respectively) that is partially bathing into the membrane bilayer. Dual fluorescence quencher analysis also revealed that helix 1 is peripherally membrane-associated, with one face of the helix dipping into the lipid bilayer and the other face projecting toward the solvent. Finally, our data suggest that the helical boundaries of helix 1, at least at the C-terminal region, remain unaffected upon binding to the surface of the membrane in support of a toroidal pore model for this colicin.

Electrochemical Dehydrogenation of 1,2,3,4‐Tetrahydroisoquinoline to 3,4‐Dihydroisoquinoline.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Photo-irradiation of α-halo carbonyl compounds: a novel synthesis of α-hydroxy- and α,α′-dihydroxyketones

The reaction of α-halo ketones (α-iodocycloalkanones, α-bromocycloalkanones, α-iodo-β-alkoxy esters, and α-iodoacyclicketones) with irradiation under a high-pressure mercury lamp gave the corresponding α-hydroxyketones in good yields. For α-bromoketones, it was found that α-hydroxylation does not occur. However, α-bromoketones were converted into α-hydroxyketones in the presence of KI. In the case of α,α′-diiodo ketones, α,α′-dihydroxyketones, which up to now have scarcely been reported, were obtained. This reaction affords a new, clean and convenient synthetic method for α-hydroxy- and α,α′-dihydroxyketones.

Electrochemical Dehydrogenation of 1,2,3,4-Tetrahydroisoquinoline to 3,4-Dihydroisoquinoline

Dehydrogenation of 1,2,3,4-tetrahydroisoquinoline to 3,4-dihydroisoquinoline was carried out using an electrochemical method in the presence of KI. In this method, the iodide ion presumably played an important role as an electron carrier.

SYNTHESIS OF SOME NEW 4-AMINO-1,2,4-TRIAZOLE DERIVATIVES AS POTENTIAL ANTI-HIV AND ANTI-HBV

Some novel [1,2,4]triazolo[3,4-b][1,3,4]thiadiazolylisoindole-1,3-dione 2a–c were prepared by heating 4-amino-5-aryl-1,2,4-triazole-3-thiones 1a–c with different (1,3-dioxo-1,3-dihydro-isoindol-2-yl) carboxylic acids in POCl3. Compounds 2a, b were hydrolyzed using HCl to yield [1,2,4]triazolo[3,4-b][1,3,4]thiadiazolyl-alkylamines 3a, b. Coupling 1a, c with 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide (ABG) afforded the corresponding S-glucosides 4a, b, which on oxidation with KMnO4 gave the corresponding sulfone 5. Treatment 1b, c with diphenyl diazomethane afforded benzhydrylsulfanyltriazolylamines 7a, b. 1,8-Bis-(4-chloro-phenyl)-bis[1,2,4]triazolo[3,4-c-,4′,3′-e][1,2,4,5]dithiadiazine 8 was formed by oxidation of 1b with lead tetracetate. Compound 1c reacted with morpholine in the presence of KI and I2 to give the triazolodisulfide9.

Halogenating and Nitrating Activity of Reagents Based on Sodium Nitrate and Alkali Metal Halides in Acetic Acid

Alkali metal halides NaF, KCl, and KBr sharply enhance the nitrating activity of sodium nitrate in acetic acid with respect to 9-methylcarbazole. In the presence of KI and KBr, both nitration and halogenation of the substrate occurs, while KCl and NaF promote only the nitration process. The results may be interpreted in terms of formation of the corresponding nitryl halides XNO2 (X = F, Cl, Br, I) whose structure and reactivity were examined in the framework of the density functional theory (DFT B3LYP/3-21G*).

Electrochemical Formation of Methoxy‐ and Cyano(phenylazo)alkanes from Aldehyde and Ketone Phenylhydrazones.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Quantum chemical studies on the inhibition efficiencies of some piperazine derivatives for the corrosion of steel in acidic medium

Computational calculations on some piperazine derivatives those behave as corrosion inhibitor for steel in presence of KI in sulphuric acid of different normality in gas and aqueous phases using semi-empirical methods (i.e. MINDO/3, MNDO, PM3 and AM1) were carried out to search possible correlation between corrosion rates and geometric structures, charges on nitrogen atoms, highest occupied molecular energy level ( E HOMO), lowest unoccupied molecular energy level ( E LUMO), the differences between highest occupied molecular orbital energies and lowest unoccupied molecular orbital energies ( E HOMO− E LUMO) were carried out. The obtained correlations were satisfactory.

Diiodination of Alkynes in Supercritical Carbon Dioxide

AbstractA general, green and efficient method for the synthesis of trans‐diiodoalkenes in CO2 (sc) has been developed. Trans‐diiodoalkenes were obtained stereospecifically in quantitative yields via diiodination of both electron‐rich and electron‐deficient alkynes in the presence of KI, Ce(SO4)2 and water in supercritical carbon dioxide [CO2(sc)] at 40 °C.