- Influence of Oxidation of Pd/Al2O3 for the Reactions of CO with NH3 and Formamide Decomposition
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The reaction of CO with NH3 and the decomposition reactions for HNCO and formamide over Pd/Al2O3 films have been investigated by infrared spectroscopy.The formation of isocyanate species (NCO) was observed during all of these reactions over preoxidized Pd/Al2O3, but not over prereduced surfaces.These NCO species were formed Pd but spilled over to the Al2O3 support.Palladium became reduced during the course of the reaction of CO with NH3.A mechanism is proposed in which the reduction of Pdδ+ and the formation of a Pd formamide species are key features.
- Paul, D. K.,Worley, S. D.
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- Synthesis, application and AIE properties of novel fluorescent tetraoxocalix[2]arene[2]triazine: The detection of a hazardous anion, cyanate
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A highly effective, new heterocalixarene fluorescent receptor comprised of 2-(2-aminophenyl)benzothiazole and tetraoxacalix[2]arene[2]triazine was designed and synthesized by one-step reaction. The sensor candidate exhibiting aggregation induced emission (AIE) was tested for its photophysical behaviour towards detection of various anions. The results showed that our receptor undergo AIE in >40% H2O-DMSO along with large pseudo Stokes shift (Δλ = 219 nm) and exhibit selective and sensitive detection towards hazardous cyanide's oxidation product, cyanate (CNO-) ion over other tested anions. The blue-shifted fluorescence emission (λem = 492 nm) enhancement with large Stokes shift (Δλ = 144 nm) was observed with the increase in cyanate concentration. The synthesized turn-on sensor towards cyanate detection could be applied in real sample analyses as an improvement to the method currently carried out by international standards and hereby a different approach has been made for the detection of cyanide through its oxidation form, cyanate.
- Bozkurt, Selahattin,Halay, Erkan
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- Infrared spectrum of solid isocyanic acid (HNCO): Vibrational assignments and integrated band intensities
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Characterization of infrared spectra thin films of solid HNCO condensed from the gas phase was reported. It was characterized in terms of integrated band intensities, vibrational frequencies and mode assignments. Reaction of Isocyanic acid with water (Hs
- Lowenthal,Khanna,Moore, Marla H.
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- Thermal properties of cyanatocopper(II) complexes with pyridine, bipyridine and phenanthroline
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The thermal properties of cyanatocopper complexes with pyridine, bipyridine and phenanthroline are described in this paper. It was found that the thermal stabilities of the complexes were found to increase in the order py?bipy2(NCS)2 (L=pyridine and its methyl derivates) which are composed of the liberation of ligands L and redox reactions of thiocyanate ligands with the central Cu(II) atom [1,2]. The decomposition temperature of thiocyanate ligands depends on the properties of the ligands L present in the coordination sphere. An analogous course of thermal decomposition was also observed for [Cu(bipy)2(NCX)](NCX) (X=S or Se) [3]. For the phenanthroline complexes [Cu(phen)2(NCX)2] (X=S or Se) the thermal stability was found to increase significantly (by about 140°C) and the decomposition stoichiometry was also changed [3]. The present paper contains the results of thermoanalytical studies on bipyridine and phenanthroline cyanatocopper complexes, and a comparison of the thermal properties of pyridine cyanato and isothiocyanatocopper complexes.
- Kabesova,Jorik
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- Infrared Study of Ammonia-Carbon Monoxide Reaction on Silica-supported Iron Catalysts
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Infrared spectroscopy has been used to study the reaction of carbon monoxide and ammonia over Fe/SiO2 catalyst at ca. 298-723 K.Adatoms of nitrogen resulting from the dissociative adsorption of ammonia reacted with CO to form surface isocyanate on iron at
- Johnson, Colin,Jorgensen, Norman,Rochester, Colin H.
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- Furier Transform Infrared Studies of the Irreversible Oxidation of Cyanide at Platinum Electrodes
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The behaviour of cyanide on platinum electrodes at anodic potentials has been studied by voltammetric and Furier transform infrared reflectance spectroscopic techniques.The voltammetry shows that cyanide adsorbs on platinum at potential more negative than -0.8 V (SCE).Potential-sensitive infrared absorptions appearing between 2200 and 2250 cm-1 are tentatively assigned to strongly adsorbed cyanide species.Another band at 2074.5 cm-1 shows no change in wavenumber with potential and is thought to be associated with cyanide in the double-layer region.An absorption at 2169 cm-1, which appears with significant intensity at anodic potentials, has been attributed to bulk cyanate.Other features at 2093 and 2343 cm-1 are assigned to aqueous hydrogen cyanide and carbon dioxide, respectively, possibly formed as a result of changes in interfacial pH associated with electro-oxidation.
- Hinman, A. Scott,Kydd, Ronald A.,Cooney, Ralph P.
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- FORMATION OF ISOCYANATES ON NOBLE METALS AND SUPPORTED NOBLE METAL CATALYSTS.
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The formation of support-NCO and noble metal-NCO groups on oxide supported noble metal catalysts and high area evaporated metal films during the NO/CO reaction was studied by FTIR spectroscopy. With SiO//2 and Al//2O//3 as supports the results reported in the literature were essentially reproduced. With TiO//2 and ZrO//2 absorption bands in the region between 2000 and 2100 cm** minus **1 were detected, which had not been described before. On evaporated metals NCO-groups could be detected in situ. They are located at 2185 cm** minus **1 for Pd and at 2170 cm** minus **1 for Pt. Based on kinetic measurements the spillover of NCO-groups from the noble metal to the support is proposed as a mechanism for support-NCO formation.
- Schuth,Wicke
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- A Multifunctional Bimetallic Molecular Device for Ultrasensitive Detection, Naked-Eye Recognition, and Elimination of Cyanide Ions
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A new bimetallic FeII-CuII complex was synthesized, characterized, and applied as a selective and sensitive sensor for cyanide detection in water. This complex is the first multifunctional device that can simultaneously detect cyanide ions in real water samples, amplify the colorimetric signal upon detection for naked-eye recognition at the parts-per-million (ppb) level, and convert the toxic cyanide ion into the much safer cyanate ion in situ. The mechanism of the bimetallic complex for high-selectivity recognition and signaling toward cyanide ions was investigated through a series of binding kinetics of the complex with different analytes, including CN-, SO42-, HCO3-, HPO42-, N3-, CH3COO-, NCS-, NO3-, and Cl- ions. In addition, the use of the indicator/catalyst displacement assay (ICDA) is demonstrated in the present system in which one metal center acts as a receptor and inhibitor and is bridged to another metal center that is responsible for signal transduction and catalysis, thus showing a versatile approach to the design of new multifunctional devices.
- Chow, Cheuk-Fai,Ho, Pui-Yu,Wong, Wing-Leung,Gong, Cheng-Bin
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- Photocatalytic Oxidation of Cyanide on Platinized TiO2
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The photocatalytic oxidation of cyanide on platinized TiO2 was studied mainly from the standpoint of semiconductor electrochemistry to elucidate the role of platinum deposited on TiO2 photocatalysts.It was found that platinization enhances the rate of the oxygen reduction which constitutes a partial process of the photocatalytic reaction, but suppresses the rate of photosensitized oxidation as the counter partial process in which cyanide is oxidized competitively with water.The activities of single crystal and powder TiO2 catalysts for photocatalytic reaction were compared for cases with and without 50 monolayers of Pt.They were found comparable in spite of a large surface area of the latter, suggesting that the number of photons striking the catalyst surface entirely controls the rate of photocatalytic reaction.Effects of platinization on the electrochemical properties of TiO2, evaluation of the rate of photocatalytic reaction by electrochemical analyses, and effects of illumination on the photocatalytic process are discussed.
- Kogo, Katsuyuki,Yoneyama, Hiroshi,Tamura, Hideo
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- Photocatalytic oxidation of cyanide: Kinetic and mechanistic studies
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The kinetics and mechanism of the photocatalytic oxidation of cyanide in the presence titanium dioxide catalyst were investigated in this study. By displacing the surface hydroxyl groups on the surface of titanium dioxide with fluoride ions, it was deduced that cyanide is oxidised via a pure heterogeneous pathway, i.e. oxidised by the holes trapped at the surface hydroxyl groups ≡TiO.. The quantum efficiency of the photocatalytic oxidation was found to be low (ca. 0.1-0.2%) and this was mainly due to (1) the low adsorption of cyanide ions onto the titanium dioxide surface, (2) the absence of homogenous reaction between cyanide ions and diffused hydroxyl radicals, and (3) the high electron hole recombination rate within the titanium dioxide photocatalyst. A kinetic model was developed to describe the mechanism involved in the photocatalytic oxidation of cyanide.
- Chiang,Amal,Tran
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- Velocity modulation infrared laser spectroscopy of negative ions: The ν3, ν3+ν1-ν1, ν3+ν2-ν2, and ν3+2ν2-2ν2 bands of cyanate (NCO-)
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(Received 26 January 1987; accepted 6 March 1987) We have measured 132 transitions in the ν3 (CN stretching) fundamental and the corresponding bending and stretching hotbands of the cyanate anion, ranging from P(52) to R(66), with a tunable diode laser using the velocity modulation technique.The spectra were fit to the standard linear triatomic molecule rotation-vibration Hamiltonian, yielding efiective molecular parameters for the (0000), (O110), (0200), ( 1O0O), (0001 ), (O111), (0201 ), and ( 1001 ) states.The equilibrium rotational constant was determined to be Be = 0.385 933 ( 116) cm-1.A comparison with condensed phase results is presented.As previously oberved for N3- 3, cyanate is detected with high vibrational excitation in the bending mode, most likely as a consequence of the formation mechanism.
- Gruebele, Martin,Polak, Mark,Saykally, Richard J.
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- Cu (I) Catalyzed One Pot SN-Click Reactions of Halogenated Coumarins and 1-aza-coumarins
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A one pot three component, copper catalyzed azide-alkyne cycloaddition reaction has been employed for the synthesis of bis-coumarinyl triazoles (A–D) using 4-chloro, 4-bromomethyl, 3-bromoacetyl and 4-bromomethyl-1-aza-coumarins (I–IV), sodium azide, and coumarin propargyl ethers (V–IX) in moderate yields.
- Revankar, Hrishikesh M.,Kulkarni, Manohar V.
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p. 537 - 544
(2018/01/10)
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- Click chemistry approach for the regioselective synthesis of iso-indoline-1,3-dione-linked 1,4 and 1,5 coumarinyl 1,2,3-triazoles and their photophysical properties
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Copper-catalyzed reaction of N-propargyl isoindoline-1,3-dione and 4-azidomethyl coumarins / 4-azidomethyl-1-aza coumarins under click chemistry conditions afforded 1,4-disubstituted 1,2,3-triazoles, whereas ruthenium catalysis yielded isomeric 1,5-disubstituted 1,2,3-triazoles. The two regioisomers have been distinguished by NOE studies. UV absorption for a given pair of isomers exhibited similar trend, whereas fluorescence measurements showed considerable differences. Photo physical studies on the interaction of azides with copper and ruthenium have also been performed.
- Anand, Ashish,Kulkarni, Manohar V.
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p. 722 - 733
(2017/03/27)
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- Catalyst displacement assay: A supramolecular approach for the design of smart latent catalysts for pollutant monitoring and removal
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Latent catalysts can be tuned to function smartly by assigning a sensing threshold using the displacement approach for targeted analytes. Three cyano-bridged bimetallic complexes were synthesized as smart latent catalysts through the supramolecular assembly of different metallic donors [FeII(CN)6]4-, [FeII(tBubpy)(CN)4]2-, and FeII(tBubpy)2(CN)2 with a metallic acceptor [CuII(dien)]2+. The investigation of both their thermodynamic and kinetic properties on binding with toxic pollutants provided insight into their smart off-on catalytic capabilities, enabling us to establish a threshold-controlled catalytic system for the degradation of pollutants such as cyanide and oxalate. With these smart latent catalysts, a new catalyst displacement assay (CDA) was demonstrated and applied in a real wastewater treatment process to degrade cyanide pollutants in both domestic (level I, untreated) and industrial wastewater samples collected in Hong Kong, China. The smart system was adjusted to be able to initiate the catalytic oxidation of cyanide at a threshold concentration of 20 μM (the World Health Organization's suggested maximum allowable level for cyanide in wastewater) to the less harmful cyanate under ambient conditions.
- Chow, Cheuk-Fai,Ho, Pui-Yu,Wong, Wing-Leung,Lu, Yu-Jing,Tang, Qian,Gong, Cheng-Bin
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p. 3812 - 3820
(2017/07/11)
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- Synthesis and anti-bacterial evaluation of 4-aryloxymethyl carbostyrils derived from substructures and degradation products of Vancomycin
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Vancomycin has been used as an antibiotic selectively against Gram-positive bacteria; however in the past decade they have grown resistant against it. The present work describes synthesis of a series of 4-aryloxymethyl carbostyrils derived from the reaction of 4-bromomethyl carbostryils with degradation products of Vancomycin (ethyl gallate and ethyl ester of N-benzoyl tyrosine ethyl ester). Further, gallate ethers 4a-d and tyrosine ethers 5a-d have been found to be selectively active against Gram-positive bacteria.
- Revankar, Hrishikesh M.,Arali, Shweta,Yakkerimath, Shilpa,Revankar, Pooja P.,Naik, Vijaykumar,Anand, Ashish,Kulkarni, Manohar V.
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p. 637 - 642
(2017/01/18)
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- Environment-friendly synthetic method of 4-bromomethyl quinolinone
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The invention discloses an environment-friendly synthetic method of 4-bromomethyl quinolinone. The environment-friendly synthetic method comprises the following steps: adding acetoacetanilide bromide as a raw material into an anhydrous organic solvent; taking out moisture generated in reaction by virtue of the organic solvent as a water carrier while heating, condensing the moisture-containing organic solvent, adding the organic solvent into a reaction kettle filled with phosphorus pentoxide, and carrying out dehydration under stirring; continuously distilling the organic solvent in the reaction kettle filled with phosphorus pentoxide, returning the distilled anhydrous organic solvent to an acetoacetanilide bromide reaction kettle as the water carrier, carrying out dehydration cyclization on acetoacetanilide bromide so as to generate 4-bromomethyl quinolinone, cooling the system to the room temperature, carrying out filter pressing by directly utilizing a filter press, washing by virtue of an organic solvent, and drying, so as to obtain the product. According to the environment-friendly synthetic method, the yield of reaches 95% or above, and the purity of 4-bromomethyl quinolinone is more than or equal to 99.5%; and the product quality is good, waste acid and wastewater are not generated, the production efficiency is high, the cost is low, and large-scale production is easily realized.
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Paragraph 0016; 0017
(2016/10/27)
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- Cyclopropanes in water: A diastereoselective synthesis of substituted 2H-chromen-2-one and quinolin-2(1H)-one linked cyclopropanes
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A one-pot three component reaction has been developed for the synthesis of substituted cyclopropanes employing 4-bromomethyl-2H-chromen-2-one/quinolin-2(1H)-ones, aromatic aldehydes and activated nitriles. The room temperature reaction in aqueous medium has been found to be diastereoselective and high yielding.
- Anand, Ashish,Yenagi, Jayashree,Tonannavar,Kulkarni, Manohar V.
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supporting information
p. 2201 - 2205
(2016/04/19)
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- Designed hierarchical synthesis of ring-shaped Bi2WO 6@CeO2 hybrid nanoparticle aggregates for photocatalytic detoxification of cyanide
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Ring-shaped Bi2WO6@CeO2 hybrid nanoparticle aggregates are fabricated through an environmental route and subsequent facile calcinations. The synthetic parameters are regulated to control the shape of the as-prepared samples. The concentration of the cyanide ion decreased sharply from the initial 4.72 mM to 0.95 mM with the exposure time of 60 min. The intrinsic ring-shaped microstructure results in multiple reflections of light within the chamber, allowing more efficient use of the light source compared with a solid structure. The p-n junction effect can lead to enhanced charge separation and interfacial charge transfer efficiency due to the existence of an internal electric field. Therefore, it exhibits a remarkable photocatalytic detoxification of cyanide and degradation of dye under visible light. the Partner Organisations 2014.
- Guo, Hong,Guo, Yuanyuan,Liu, Lixiang,Li, Tingting,Wang, Wei,Chen, Weiwei,Chen, Jing
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p. 2539 - 2545
(2014/05/06)
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- Oxidation of thiocyanate with H2O2 catalyzed by [RuIII(edta)(H2O)]-
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The [RuIII(edta)(H2O)]- (edta4- = ethylenediaminetetraacetate) complex is shown to catalyze the oxidation of thiocyanate (SCN-) with H2O2 mimicking the action of peroxidases. The kinetics of the catalytic oxidation process was studied by using stopped-flow and rapid scan spectrophotometry as a function of [RuIII(edta)], [H2O2], [SCN-], pH (3.2-9.1) and temperature (15-30 °C). Spectral analyses and kinetic data are suggestive of a catalytic pathway in which hydrogen peroxide reacts directly with thiocyanate coordinated to the RuIII(edta) complex. Catalytic intermediates such as [RuIII(edta)(OOH)]2- and [Ru V(edta)(O)]- were found to be non-reactive in the oxidation process under the specified conditions. Formation of SO 42- and OCN- was identified as oxidation products in ESI-MS experiments. A detailed mechanism in agreement with the spectral and kinetic data is presented. The Royal Society of Chemistry 2013.
- Chatterjee, Debabrata,Paul, Barnali,Mukherjee, Rupa
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supporting information
p. 10056 - 10060
(2013/08/23)
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- Mechanism of decomposition of the human defense factor hypothiocyanite near physiological pH
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Relatively little is known about the reaction chemistry of the human defense factor hypothiocyanite (OSCN-) and its conjugate acid hypothiocyanous acid (HOSCN), in part because of their instability in aqueous solutions. Herein we report that HOSCN/OSCN- can engage in a cascade of pH- and concentration-dependent comproportionation, disproportionation, and hydrolysis reactions that control its stability in water. On the basis of reaction kinetic, spectroscopic, and chromatographic methods, a detailed mechanism is proposed for the decomposition of HOSCN/OSCN- in the range of pH 4-7 to eventually give simple inorganic anions including CN -, OCN-, SCN-, SO32-, and SO42-. Thiocyanogen ((SCN)2) is proposed to be a key intermediate in the hydrolysis; and the facile reaction of (SCN) 2 with OSCN- to give NCS(=O)SCN, a previously unknown reactive sulfur species, has been independently investigated. The mechanism of the aqueous decomposition of (SCN)2 around pH 4 is also reported. The resulting mechanistic models for the decomposition of HOSCN and (SCN) 2 address previous empirical observations, including the facts that the presence of SCN- and/or (SCN)2 decreases the stability of HOSCN/OSCN-, that radioisotopic labeling provided evidence that under physiological conditions decomposing OSCN- is not in equilibrium with (SCN)2 and SCN-, and that the hydrolysis of (SCN)2 near neutral pH does not produce OSCN-. Accordingly, we demonstrate that, during the human peroxidase-catalyzed oxidation of SCN-, (SCN)2 cannot be the precursor of the OSCN- that is produced.
- Kalmar, Jozsef,Woldegiorgis, Kelemu L.,Biri, Bernadett,Ashby, Michael T.
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p. 19911 - 19921
(2012/01/31)
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- DIARYLAMINE-SUBSTITUTED QUINOLONES USEFUL AS INDUCIBLE NITRIC OXIDE SYNTHASE INHIBITORS
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Novel diarylamine-substituted quinolone compounds and pharmaceutical compositions, certain of which have been found to inhibit inducible NOS synthase have been discovered, together with methods of synthesizing and using the compounds including methods for the treatment of iNOS-mediated diseases in a patient by administering the compounds.
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Page/Page column 43
(2009/04/25)
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- QUINOLONES USEFUL AS INDUCIBLE NITRIC OXIDE SYNTHASE INHIBITORS
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The present invention relates to novel quinolones of Formula I that inhibit inducible NOS synthase together with methods of synthesizing and using the compounds including methods for inhibiting or modulating nitric oxide synthesis and/or lowering nitric oxide levels in a patient by administering the compounds for the treatment of disease.
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- Synthesis and biological activities of some new fluorinated coumarins and 1-aza coumarins
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A series of new fluorinated coumarins and 1-aza coumarins have been synthesized and the presence of fluorine in these molecules and its effect on their anti-microbial, anti-inflammatory and analgesic activities are discussed. The results of bioassay showed that these newly synthesized compounds containing fluorine exhibit moderate analgesic and excellent anti-inflammatory and potential anti-bacterial and anti-fungal activities, compared to the other halogenated compounds. All the newly synthesized compounds were characterized by elemental analysis, IR, 1H NMR, 13C NMR, 19F NMR, EI-MS, and FAB-MS. The ORTEP diagram of one of the compounds is reported herein.
- Kalkhambkar, Rajesh G.,Kulkarni, Geeta M.,Kamanavalli, Chandrappa M.,Premkumar,Asdaq,Sun, Chung Ming
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experimental part
p. 2178 - 2188
(2009/04/07)
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- Ambident reactivity of the cyanate anion
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A study was conducted to investigate ambident reactivity of the cyanate anion. The study showed that the cyanate anion is an ambident nucleophile, which may react with electrophiles either at the oxygen terminus, to yield alkyl cyanates, or at the nitrogen terminus, to yield isocyanates. Equal amounts of alkyl cyanates and isocyanates were obtained, when secondary iodoalkynes were treated with silver cyanate and the formation of tert-butyl isocyanate, along with 2-methylpropene and cyanic acid. The study also investigated the possibility of SN1 reactions of cyanates proceeding with charge control to give cyanates.
- Schaller, Heike F.,Schmidhammer, Uli,Riedle, Eberhard,Mayr, Herbert
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supporting information; experimental part
p. 3866 - 3868
(2009/05/07)
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- Solubility, complex formation, and redox reactions in the Tl 2O3-HCN/CN--H2O system. Crystal structures of the cyano compounds Tl(CN)3·H2O, Na[Tl(CN)4]·3H2O, K[Tl(CN)4], and TlITlIII(CN)4 and of TlI 2C2O
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Thallium(III) oxide can be dissolved in water in the presence of strongly complexing cyanide ions. TlIII is leached from its oxide both by aqueous solutions of hydrogen cyanide and by alkali-metal cyanides. The dominating cyano complex of thallium(III) obtained by dissolution of Tl 2O3 in HCN is [Tl(CN)3(Bq)] as shown by 205Tl NMR. The Tl(CN)3 species has been selectively extracted into diethyl ether from aqueous solution with the ratio CN -/TlIII = = 3. When aqueous solutions of the MCN (M = Na+, K+) salts are used to dissolve thallium(III) oxide, the equilibrium in liquid phase is fully shifted to the [Tl(CN) 4]- complex. The Tl(CN)3 and Tl(CN) 4- species have for the first time been synthesized in the solid state as Tl(CN)3·H2O (1), M[Tl(CN) 4] (M = Tl (2) and K (3)), and Na[Tl(CN)4]·3H 2O (4) salts, and their structures have been determined by single-crystal X-ray diffraction. In the crystal structure of 1, the thallium(III) ion has a trigonal bipyramidal coordination with three cyanide ions in the equatorial plane, while an oxygen atom of the water molecule and a nitrogen atom from a cyanide ligand, attached to a neighboring thallium complex, form a linear O-Tl-N fragment. In the three compounds of the tetracyano-thallium(III) complex, 2-4, the [Tl(CN)4]- unit has a distorted tetrahedral geometry. Along with the acidic leaching (enhanced by TlIII-CN- complex formation), an effective reductive dissolution of the thallium(III) oxide can also take place in the Tl 2O3-HCN-H2O system yielding thallium(I), while hydrogen cyanide is oxidized to cyanogen. The latter is hydrolyzed in aqueous solution giving rise to a number of products including (CONH2) 2, NCO-, and NH4+ detected by 14N NMR. The crystalline compounds, TlI[Tl III(CN)4], TlI2C2O 4, and (CONH2)2, have been obtained as products of the redox reactions in the system.
- Nagy, Peter,Fischer, Andreas,Glaser, Julius,Ilyukhin, Andrey,Maliarik, Mikhail,Toth, Imre
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p. 2347 - 2357
(2008/10/09)
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- Thermal reactivity of HNCO with water ice: An infrared and theoretical study
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The structure and energy of the 1:1 complexes between isocyanic acid (HNCO) and H2O are investigated using FTIR matrix isolation spectroscopy and quantum calculations at the MP2/6-31G(d,p) level. Calculations yield two stable complexes. The first and most stable one (ΔE = 23.3 kJ/mol) corresponds a form which involves a hydrogen bond between the acid hydrogen of HNCO and the oxygen of water. The second form involves a hydrogen bond between the terminal oxygen of HNCO and hydrogen of water. In an argon matrix at 10 K, only the first form is observed. Adsorption on amorphous ice water at 10 K shows the formation of only one adsorption site between HNCO and ice. It is comparable to the complex observed in matrix and involves an interaction with the dangling oxygen site of ice. Modeling using computer code indicates the formation of polymeric structure on ice surface. Warming of HNCO, adsorbed on H2O ice film or co-deposited with H2O samples above 110 K, induces the formation of isocyanate ion (OCN-) characterized by its vasNCO infrared absorption band near 2170 cm-1. OCN- can be produced by purely solvation-induced HNCO dissociative ionization. The transition state of this process is calculated 42 kJ/mol above the initial state, using the ONIOM model in B3LYP/6-31g(d,p).
- Raunier, Sébastien,Chiavassa, Thierry,Allouche, Alain,Marinelli, Francis,Aycard, Jean-Pierre
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p. 197 - 210
(2008/10/08)
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- Cyanide and chloride exchange on homoleptic gold(III) square-planar complexes: Variable pressure kinetic investigation by heteronuclear NMR
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Kinetic studies of X- exchange on [AuX4]- square-planar complexes (where X=Cl- and CN-) were performed at acidic pH in the case of chloride system and as a function of pH for the cyanide one. Chloride NMR study (330-365 K) gives a second-order rate law on [AuCl4]- with the kinetic parameters: (k2Au,Cl)298=0.56±0.03 s-1mol-1kg; ΔH2?Au,Cl=65.1±1 kJmol-1; ΔS2?Au,Cl=-31.3±3 Jmol-1K-1 and ΔV2?Au,Cl=-14±2 cm3mol-1. The variable pressure data clearly indicate the operation of an Ia or A mechanism for this exchange pathway. The proton exchange on HCN was determined by 13C NMR as a function of pH and the rate constant of the three reaction pathways involving H2O, OH- and CN- were determined: k0HCN,H=113±17 s-1, k1HCN,H=(2.9±0.7)×109 s-1mol-1kg and k2HCN,H=(0.6±0.2)×106 s-1mol-1kg at 298.1 K. The rate law of the cyanide exchange on [Au(CN)4]- was found to be second order with the following kinetic parameters: (k2Au,CN)298=6240±85 s-1mol-1kg, ΔH2?Au,CN=40.0±0.8 kJmol-1, ΔS2?Au,CN=-37.8±3 Jmol-1K-1 and ΔV2?Au,CN=+2±1 cm3mol-1. The rate constant observed varies about nine orders of magnitude depending on the pH and HCN does not act as a nucleophile. The observed rate constant of X- exchange on [AuX4]- are two or three orders of magnitude faster than the Pt(II) analogue.
- Monlien, Florence J.,Helm, Lothar,Abou-Hamdan, Amira,Merbach, André E.
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p. 257 - 269
(2008/10/08)
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- Photodissociation dynamics of the singlet and triplet states of the NCN radical
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The spectroscopy and photodissociation dynamics of the NCN radical have been investigated by fast beam photofragment translational spectroscopy. The B3∑u-←X 3∑g-, c1Πu,←a1Δ g, and d1Δu ←-a1Δg transitions were examined. The major dissociation products for the B3∑u- and c1Πu states are N2(X1∑g+) + C(3P), while the d1Δu state dissociates to N2(X1∑g-+)+ C(1D). The dissociation channel, N(4S) + CN(X2∑1) is observed for the B3∑u- state at photon energies greater than 4.9 eV, where it comprises ≈25±10% of the total signal. At all photon energies, the photofragment translational energy distributions show a resolved progression corresponding to the vibrational excitation of the N2 photofragment. The rotational distributions of the molecular fragments suggest that the dissociation pathway for the N2 loss channel involves a bent transition state while the N+CN photofragments are produced via a linear dissociation mechanism. The P(ET) distributions provide bond dissociation energies of 2.54±0.030 and 4.56±0.040 eV for the N2 and CN loss channels, respectively, yielding ΔHf,0 K(NCN)=4.83±0.030 eV.
- Bise, Ryan T.,Choi, Hyeon,Neumark, Daniel M.
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p. 4923 - 4932
(2007/10/03)
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- In situ vibrational study of the initial steps during urea electrochemical oxidation
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The electrochemical oxidation of urea has been studied by in situ Fourier transform infrared spectroscopy in supporting electrolytes of different pH. It has been found that the adsorbates and reaction products are strongly pH dependent. In acidic solutions, the urea is adsorbed through the nitrogen atoms. A two-proton loss is proposed for the adsorption process, related to an excess reversible charge at the end of the hydrogen adsorption/ desorption. Adsorbed CO is formed as a result of the hydrolysis of the urea molecule close to the platinum electrode. The main product detected has been CO2. For neutral solutions, the urea molecule leads to the formation of CNO- and [N2O2]2- ions at potentials in the double-layer region of the platinum electrode. At higher potentials, formation of NO2 and NO3- have been detected. In alkaline media the coordination of adsorbed urea depends on the potential. At lower potentials urea is coordinated through a single NH2 group, and at more anodic potentials the adsorbed urea changes to an adsorption through the oxygen atom.
- Bezerra, Aì?ngela C. S.,De Saì?, Eduardo L.,Nart, Francisco C.
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p. 6443 - 6449
(2007/10/03)
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- Kinetics and mechanism of alkaline hydrolysis of urea and sodium cyanate
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The kinetics of hydrolysis of urea has been studied in 0.5 to 3.0 mol dm-3 sodium hydroxide solution at different temperatures. Urea hydrolysis follows an irreversible first order consecutive reaction path: equation presented The variation of Klobs with [alkali] is linear at [OH-] = 5.0 to 1.5 mol dm-3, thereafter a sharp increase in the reaction rate is observed for first step hydrolysis of urea. The second step rate constant (K2obs) is found to be independent of [alkali]. Hydrolysis of urea in alkaline medium follows an elemination-addition mechanism. The reaction does not proceed through the formation and decomposition of tetrahedral intermediate. Sodium cyanate hydrolysis obeys an irreversible pseudo-first order kinetics. [OH-] has no significant effect on the rate constants. The following rate equations have been derived for the two step hydrolysis of urea. Klobs = K0 + K1[OH-](K4 + K3[OH-])/K-1 + K4 + K3[OH-] K2obs = K2Kh On the basis of observed data, probable mechanisms have been proposed.
- Khan, Zaheer,Rafiquee,Kabir-ud-din,Arif Niaz,Aziz Khan
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p. 1116 - 1119
(2007/10/03)
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- Copper-Catalysed Oxidation of Cyanide by Peroxide in Alkaline Aqueous Solution
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The oxidation of cyanide by peroxide in alkaline aqueous solution is catalysed by copper complexes.In the presence of excess cyanide, copper(II) is reduced to form the tricyanocuprate(I) complex.The cyanogen oxidation product is hydrolysed with disproportionation to cyanate and cyanide: 2CuII + 2CN(-) --> 2CuI + (CN)2; (CN)2 + 2OH(-) --> OCN(-) + CN(-) + H2O; CuI + 3CN(-) Cu(CN)3(2-).The stoichiometry and kinetics of the catalysed oxidation have been investigated.Hydrogen peroxide oxidizes coordinated cyanide with a rate that is first order in peroxide and first order in copper but independent of cyanide concentration in the presence of excess cyanide.Cu(CN)3(2-) + H2O2 --> Cu(CN)2(-) + OCN(-) + H2O; Cu(CN)2(-) + CN(-) Cu(CN)3(2-).When the excess cyanide is consumed and Cu(CN)2(-) becomes the dominant species, the reaction becomes more complex and less efficient.Under certain conditions the stoichiometry revealed a peroxide-to-Cu(CN)2(-) ratio of about 6:1, instead of the minimum of 2.5:1 required for the oxidation of the coordinated cyanide to cyanate and the CuI to Cu(OH)2.This suggests that peroxide is consumed by a copper-catalysed disproportionation, in competition with oxidation of the coordinated cyanide.An intermediate yellow complex forms while peroxide is present, before Cu(OH)2 finally precipitates.The consequence of this mechanism is that the most efficient process for the destructive oxidation of cyanide has a high cyanide-to-copper ratio, to minimize the final concentration of Cu(CN)2(-) which consumes peroxide inefficiently.The rate of the reaction depends on the concentration of copper, however, which must be large enough for a satisfactory turnover.
- Beattie, James K.,Polyblank, Gregory A.
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p. 861 - 868
(2007/10/02)
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- A Potential Surface Map of the H-/N2O System. The Gas Phase Ion Chemistry of HN2O-
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Dunkin, Fehsenfeld and Ferguson have reported that the gas phase reaction between H- and N2O in a flowing afterglow instrument forms HO- and N2 with medium efficiency.The potential surface (UMP2-FC/6-311++G**//RHF/6-311++G**) for the H-/N2O system confirms this to be the predominant reaction following initial approach of H- towards the central nitrogen of N2O to form unstable intermediate -(N2O)>.The intermediate then decomposes to HO- and N2 via a deep channel.The potential surface also shows the direct formation of adducts -O-+N(H)=N- and cis HN=NO-.However these are formed with excess energy: the former converts principally into reactants, while the latter decomposes to HO- and N2. Ions having the formula 'HN2O-' may be formed in the gas phase by the reactions (i) HNO- + N2O --> HN2O- + NO, and (ii) NH2- + Me3CCH2ONO --> HN2O- + Me3CCH2OH.The product anion is stabilized by removal of some of its excess energy by the eliminated neutral.Evidence is presented which indicates that the product is either cis or trans HN=NO-, or a mixture of both .The characteristic ion molecule reaction of HN=NO- involves oxidative oxygen transfer to suitable neutral substrates.For example: HN2O- + CS2 --> HS- + N2 + COS.
- Sheldon, John C.,O'Hair, Richard A. J.,Downard, Kevin M.,Gronert, Scott,Krempp, Michele,et al.
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p. 155 - 166
(2007/10/02)
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- Complex Oligooscillatory Behavior in the Reaction of Chlorite with Thiocyanate
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The reaction of chorite and thiocyanate has been studied in the pH range 1-4.The stoichiometry of the reaction is 2ClO2- + SCN- + H2O -> SO42- + 2Cl- + HOCN + H+.In excess ClO2-, ClO2(aq.) is formed as a product at the end of the reaction.ClO2 is formed from the reaction of excess ClO2- with HOCl: 2ClO2- + HOCl + H+ -> 2ClO2 + Cl- + H2O.At pH less then 4 and in excess SCN-, ClO2 is formed as an intermediate but is totally consumed at the end of the reaction.The reaction is very complex with oligooscillatory behavior in which ClO2 concentration goes through two maxima during the course of the reaction.The reaction is catalyzed by acid in pH range 2-4 but is retarded by acid in pH less than 2.The rate-determining step involves the reaction Cl(III) + SCN- + H+ -> HOSCN + HOCl.The acid retardation is due to the fact that ClO2- is more reactive than HClO2 and SCN- is a better nucleophile than isothiocyanic acid, HNCS.The reaction is autocatalytic in HOCl.The autocatalysis can be explained by using the asymmetric intermediate, Cl2O2, which produces two HOCl molecules after a two-electron reduction.The reaction of ClO2(aq) with SCN- was also studied, and it gives an autocatalytic rate of decay of ClO2.The mechanism involves initially forming ClO2- in an one-electron reduction followed by HOCl autocatalysis.Direct reaction between ClO2- and SCN- could be followed by using the FeSCN2+-SCN- reaction, which also showed acid retardation and HOCl autocatalysis.A 21-reaction mechanism was used to simulate the ClO2-SCN- reaction while a 24-reaction scheme was used to simulate the ClO2--SCN- reaction.There is resonable agreement between experiments and simulations in both cases.
- Chinake, Cordelia R.,Mambo, Elisabeth,Simoyi, Reuben H.
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p. 2908 - 2916
(2007/10/02)
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- Non-metal redox kinetics: Hypobromite and hypoiodite reactions with cyanide and the hydrolysis of cyanogen halides
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Pulsed-accelerated-flow spectroscopy is used to measure second-order rate constants (where the initial half-lives are 3-9 μs) for the reactions of cyanide ion with OBr- and with OI- (25.0°C, μ = 1.00 M). The proposed mechanism includes parallel paths with halogen-cation transfer to CN- by solvent-assisted reaction with OX- (X = Br, I) and by direct reaction with HOX: OX- + CN- + H2O → kox XCN + 2OH- OX- + H2O ? HOX + OH- HOX + CN- → kHOX XCN + OH- The relative reactivities of the hypohalites with CN- (kox) are as follows: OI- (6 × 107 M-1 s-1) ≈ OBr- (5.7 × 107 M-1 s-1) ? OCl- (310 M-1 s-1). The rate constants for the hypohalous acid reactions with CN- (kHOX) are as follows: HOBr (4.2 × 109 M-1 s-1) > HOCl(1.22 × 109 M-1 s-1). The base hydrolysis of ICN is studied spectrophotometrically by the appearance of I- at 225 nm (ε = 12 070 M-1 cm-1). Saturation kinetics are observed with increased OH- concentration. This is attributed to rapid equilibration to give HOICN- (KOH = 3.2 M-1), which inhibits the OH- attack at the carbon atom in ICN to form OCN- (k4 = 1.34 × 10-2M-1s-1). The base hydrolysis of BrCN is studied by following the disappearance of the 105 amu peak with membrane introduction mass spectrometry. Rate constants for the reactions of BrCN with OH- (kOH = 0.53 ± 0.01 M-1 s-1) and with CO32- are determined (kCO3 = (7.5 ± 0.3) × 10-3 M-1 s-1). The relative reactivities of cyanogen halides for the base hydrolysis are as follows: ClCN ? BrCN ? ICN.
- Gerritsen, Cynthia M.,Gazda, Michael,Margerum, Dale W.
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p. 5739 - 5748
(2008/10/08)
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- Photoelectron spectroscopy of CN-, NCO-, and NCS-
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The 266 nm photoelectron spectra of CN-, NCO-, and NCS- have been recorded with a pulsed time-of-flight photoelectron spectrometer.The photoelectron spectrum of CN- has also been recorded at 213 nm revealing transitions to the A 2Π state as well as the ground X 2Σ+ state of the CN radical.The following adiabatic electron affinities (EAs) are determined: EA(CN)=3.862+/-0.004 eV, EA(NCO)=3.609+/-0.005 eV, and EA(NCS)=3.537+/-0.005 eV.The adiabatic electron affinity of cyanide is in disagreement with the currently accepted literature value.Our measurement of the electron affinity of NCS confirms recent theoretical estimates that dispute the literature experimental value.By Franck-Condon analysis of the vibrational progressions observed in each spectrum, the change in bond lengths between anion and neutral are also determined.For NCO- this yields R0(C-N)=1.17+/-0.01 Angstroem and R0(C-O)=1.26+/-0.01 Angstroem, and for CN- the equilibrium bond length is found to be Re(C-N)=1.177+/-0.004 Angstroem.The gas phase fundamental for CN- is determined for the first time: ν=2035+/-40 cm-1.
- Bradforth, Stephen E.,Kim, Eun Ha,Arnold, Don W.,Neumark, Daniel M.
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p. 800 - 810
(2007/10/02)
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- Reduction of the tetrahydroxoargentate(III) ion by thiocyanate in aqueous alkaline media
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The reduction of Ag(OH)4- by thiocyanate ion in the range 5 × 10-4 ≤ [SCN-] ≤ 0.25 M was studied in aqueous alkaline media at 25°C and μ = 1.2 M by stopped-flow spectrophotometry. At [SCN-] ≤ 0.01 M, the reaction was found to be first-order in each reactant, with an apparent second-order rate constant of 21.7 ± 0.3 M-1 s-1. At higher thiocyanate concentrations, silver(III) disappearance continues to appear pseudo first order, but the thiocyanate dependence becomes complex. Oxidation products are SO42-, OCN-, and (at high SCN- only) cyanide ion. A mechanism is proposed consisting of a series of two-electron redox steps. Competition between SCN- and reaction intermediates for remaining silver(III) accounts for changes in both rate and product distribution. The activation enthalpy and entropy for the initial step are 28.3 ± 1.2 kJ mol-1 and -129 ± 7 J mol-1 K-1 respectively. Numerical simulation and reaction with potential intermediates have been used to support the conclusions.
- Kirschenbaum, Louis J.,Sun, Yunfu
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p. 2360 - 2365
(2008/10/08)
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- Kinetics of oxidation of thiocyanate ion and benzyl alcohol by diperiodatonickelate(IV) in aqueous alkaline medium
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Kinetics of oxidation of thiocyanate ion and of benzyl alcohol by diperiodatonickelate(IV) have been studied in aqueous alkaline medium (pH between 8 and 10).Both the title reactions exhibit similar kinetics.The orders in benzyl alcohol and thiocyanate ion have been found to be unity each.The rate of the oxidation increases with increase in ->; however, added retards the rate.Effect of salts and change in dielectric constant of the medium affect the rate of oxidation of thiocyanate but no such effect has been observed in benzyl alcohol oxidation.Monoperiodatonickelate(IV) has been found as the reactive species of oxidant from salt effect studies.Suitable mechanisms are proposed.
- Khan, Jaffar Ali,Chandraiah, U.,Kumar, B. Kishore,Kandlikar, Sushama
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p. 241 - 244
(2007/10/02)
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- Non-metal redox kinetics: Hypochlorite and hypochlorous acid reactions with cyanide
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The rate expression for OCl- oxidation of CN- is -d[OCl-]/dt = (k1 + k2/[OH-])[CN-][OCl-], where k1 is 310 M-1 s-1 and k2 is 583 s-1 (25.0°C, μ = 1.00 M). The observed inverse [OH-] dependence is due to the great reactivity of HOCl, which is 3.9 × 106 times more reactive than OCl- with CN-. The proposed mechanism with HOCl is OCl- + H2O ?k-3k3 HOCl + OH- HOCl + CN- →k4 CNCl + OH- CNCl + 2OH- → OCN- + Cl- + H2O where k4 is 1.22 × 109 M-1 s-1, on the basis of pKa = 7.47 for HOCl at μ = 1.00 M, 25.0°C. At high CN- concentration the HOCl reaction becomes so fast that proton-transfer reactions from H2O to OCl- and from HCN to OCl- OCl- + HCN ?k-5k5 HOCl + CN- contribute to the rate, where the values for k3 and k-3 are 9 × 103 s-1 and 1.9 × 1010 M-1 s-1 and the values for k5 and k-5 are 2.2 × 107 M-1 s-1 and 6.6 × 108 M-1 s-1. Rate constants for Cl+ transfer from HOCl to nucleophiles decrease in value by 10 orders of magnitude with CN- ≥ SO32- > I- ? Br- ? Cl-, in accord with the decrease of anion nucleophilicity.
- Gerritsen, Cynthia M.,Margerum, Dale W.
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p. 2757 - 2762
(2008/10/08)
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- Kinetics and Mechanism of Oxidation of Thiocyanate Ion by Chloramine-B and Bromamine-B in Alkaline Medium
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Kinetics and mechanism of oxidation of thiocyanate ion (NCS(-)) by chloramine-B (CAB) and bromamine-B (BAB) have been studied in the alkaline medium over a wide range of and .The order in is unity over the entire range of (0.01-0.5 mol dm-3), fractional in and inverse fractional in .The order in is unity, zero in and fractional in .Effects of added reaction products and variations in ionic strength and dielectric constant of the reaction medium on the rate have also been investigated.Mechanism in conformity with the observed kinetics have been proposed and the corresponding rate laws deduced.The activation parameters have been computed from the rate constants of the rate-determining steps.
- Gowda, B. Thimme,Bhat, J. Ishwara
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p. 215 - 219
(2007/10/02)
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- Gas-Phase Negative Ion Chemistry of Methyl Isocyanide
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The gas-phase negative ion chemistry of methyl isocyanide (CH3NC) has been studied at 0.4 Torr in a flowing afterglow apparatus and compared with that of its isomer acetonitrile (CH3CN).Methyl isocyanide has been determined to be 1.8 +/- 0.4 kcal/mol less acidic than acetonitrile in the gas phase, yielding ΔH0 acid(CH3NC) = 374 +/- 3 kcal/mol.The isocyano group has been found to stabilize an adjacent radical site better than does the cyano group.Methyl isocyanide reacts with bases by competing proton abstraction and SN2 processes.The reaction of the isocyanomethyl anion with a number of neutral reagents has also been studied.It undergoes hydrogen-deuterium exchange with D2O while cyanide ion is a major product upon reaction with O2, SO2, N2O, COS, CS2, and C6H5CHO.Other ions are also produced in smaller amounts with many of these reagents.The rates of reaction of the isomeric anions with CH3Br have also been determined.
- Filley, Jonathan,DePuy, Charles H.,Bierbaum, Veronica M.
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p. 5992 - 5995
(2007/10/02)
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- Carbostyril derivatives
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Disclosed are carbostyril derivatives and their salts of the formulas STR1 The compounds have anti-peptic ulcer effects, and are useful as a treating agent for curing peptic ulcers in the digestive system, such as ulcers in the stomach and in the duodenum. The compounds particularly have prophylaxis and curing effects for treating chronic ulcers, for example experimental acetic acid-induced ulcers and cautery ulcers, with both low toxicity and few side-effects. Also disclosed are processes for preparing the compounds and for preparing pharmaceutical compositions containing them.
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- Gas-phase reactions of the hydroperoxide and performate anions
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The flowing afterglow technique has been used to study the reactions of HO2- and HCO3- in the gas phase.The hydroperoxide ion reacts slowly with CO to form HO-, and oxidizes CO2, OCS, CS2, NO, SO2, CH3NCS in fast reactions to form CO3-, CO2S-, COS2-, NO2-, SO3-, CH3NCO2-, and CH3NCOS-, respectively.Reactions of HO2- with certain amides and esters provide synthetic routes for a number of interesting peracyl anions.One of these, the peroxyformate ion, HCO3-, reacts with CO and NO in slow oxidation reactions to form the formate ion HCO2-.It also forms HCO2- upon reaction with acetone and pivalaldehyde, perhaps by Baeyer-Villiger oxidation.
- Bowie, John H.,DePuy, Charles H.,Sullivan, Sally A.,Bierbaum, Veronica M.
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p. 1046 - 1050
(2007/10/02)
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- Gas-Phase Synthesis and Reactions of Nitrogen- and Sulfur-Containing Anions
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The flowing afterglow and selected ion-flow tube techniques have been used to study the reactions of H2N- with N2O, CO2, CS2, SO2, and OCS in the gas phase.Thermal energy rate coefficients and product branching ratios have been determined and are discussed in terms of detailed reaction mechanisms.With use of the SIFT-drift technique, the product distribution for the reaction of H2N- with N2O was measured as a function of the center of mass kinetic energy in the range of thermal energy to ca. 15 kcal mol1-.Qualitative studies were made of the reactions of HO-, CH3O-, and (CH3)2N- with N2O, CO2, CS2, SO2, and OCS, and the reactions of a variety of other ions with OCS were also examined.These reactions provide efficient synthetic routes for the gas-phase preparation of a variety of interesting negative ions containing nitrogen and sulfur.The basicities and heats of formation of three of these anions, H2NS-, NSO-, and NCS-, have been bracketed by proton-transfer reactions.The nucleophilicities of these three anions, as well as of H2N-, HO-, HO2-, F-, HS-, CN-, NCO-, N3-, Cl-, and Br- toward CH3I, have been measured.
- Bierbaum, Veronica M.,Grabowski, Joseph J.,DePuy, Charles H.
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p. 1389 - 1393
(2007/10/02)
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