RESUMEN
1,3-Diamines are an important class of compounds that are broadly found in natural products and are also widely used as building blocks in organic synthesis. Although the intramolecular C-H amination of N-alkylsulfamide derivatives is a reliable method for the construction of 1,3-diamine structures, the majority of these methods involve the use of a transition-metal catalyst. We herein report on a new transition-metal-free method using tert-butyl hypoiodite (t-BuOI) or N-iodosuccinimide (NIS), enabling secondary non-benzylic and tertiary C-H amination reactions to proceed. The cyclic sulfamide products can be easily transformed into 1,3-diamines. Mechanistic investigations revealed that amination reactions using t-BuOI or NIS each proceed via different pathways.
Asunto(s)
Aminación , Compuestos de Yodo/química , SuccinimidasRESUMEN
Iodine-based contrasting agents for computed tomography (CT) have been used for decades in medicine. Agents like Lugol's iodine enhance the contrasts between soft tissues and mineralized (skeletal) tissues. Because a recent study on extant avian heads showed that iodine-ethanol (I2 E) is a better contrast enhancer overall than the standard Lugol's iodine, here, we tested if I2 E could also enhance the CT contrasts of two fossilized skeletal tissues: bone and calcified cartilage. For this, we used a partial ankle joint from an extinct pheasant from the Late Miocene of Northwest China (Linxia Basin). The pre-staining CT scans showed no microstructural details of the sample. After being immersed into a solution of 1% I2 E for 8 days and scanned a second time, the contrasts were drastically enhanced between the mineralized tissues (bony trabeculae and calcified cartilage) and the sediments and minerals inside vascular spaces. After three other staining-scanning cycles in 2%, 3%, and 6% I2 E solutions, the best contrasts were obtained after immersion in 6% I2 E for 7 days. Energy Dispersive Spectroscopy showed that iodine was preferentially absorbed by the mineralized tissues and the minerals in the vascular spaces, but not by the sediments. This method not only effectively increased the contrasts of two different fossilized skeletal tissues, it was also non-destructive and reversible because part of the fossil was successfully de-stained after a few days in pure ethanol. These preliminary results indicate that iodine-ethanol has the potential to be used widely in vertebrate paleontology to improve CT imaging of fossilized tissues.
Asunto(s)
Alcoholes/química , Aves/anatomía & histología , Medios de Contraste , Fósiles/anatomía & histología , Compuestos de Yodo/química , Tomografía Computarizada por Rayos X/métodos , Animales , Imagenología Tridimensional/métodosRESUMEN
For a very long time, frequent occurrences of biocrises have wreaked havoc on human beings, animals, and the environment. As a result, it is necessary to develop biocidal agents to destroy or neutralize active agents by releasing large amounts of strong biocides which are obtained upon detonation. Iodine is an efficient biocidal agent for bacteria, fungi, yeasts, viruses, spores, and protozoan parasites, and it is the sole element in the periodic table that can destroy microbes without contaminating the environment. Based on chemical biology, the mechanism of iodine as a bactericide may arise from oxidation and iodination reactions of cellular proteins and nucleic acids. However, because of the high vapor pressure causing elemental iodine to sublime readily at room temperature, it is inconvenient to use this material in its normal solid state directly as a biocidal agent under ambient conditions. Iodine-rich compounds where iodine is firmly bonded in molecules as a C-I or I-O moiety have been observed to be among the most promising energetic biocidal compounds. Gaseous products comprised of large amounts of iodine or iodine-containing components as strong biocides are released in the decomposition or explosion of iodine-rich compounds. Because of the detonation pressure, the iodine species are distributed over a large area greatly improving the efficacy of the system and requiring considerably less effort compared to traditional biocidal methods. The commercially available tetraiodomethane and tetraiodoethene, which possess superb iodine content also have the disadvantages of volatility, light sensitivity, and chemically reactivity, and therefore, are not suitable for use directly as biocidal agents. It is absolutely critical to synthesize new iodine-rich compounds with good thermal and chemical stabilities.In this Account, we describe our strategies for the syntheses of energetic iodine-rich compounds while maintaining the maximum iodine content with concomitant stability and routes for the synthesis of oxygen-containing iodine-rich compounds to improve the oxygen balance and achieve both high-energy and high-iodine content. In the other work, which involves cocrystals, iodine-containing polymers were also summarized. It is hoped that this Account will provide guidelines for the design and syntheses of new iodine-rich compounds and a route for the development of inexpensive, more efficient, and safer iodine-rich antibiological warfare agents of the future.
Asunto(s)
Desinfectantes/química , Compuestos de Yodo/química , Bacterias/efectos de los fármacos , Desinfectantes/síntesis química , Desinfectantes/farmacología , Compuestos de Yodo/síntesis química , Compuestos de Yodo/farmacología , Estructuras Metalorgánicas , Oxidación-Reducción , Triazoles/químicaRESUMEN
Photocatalysis is extensively investigated as a green, efficient and promising technique for environmental remediation. In this study, a series of template free In-doped BiOBrxI1-x photocatalysts have been successfully prepared at room temperature and characterized by various methods. Complete degradation of negatively charged methyl Orange, positively charged Rhodamine B and Methylene Blue organic dyes, and neutral and colorless non-dye organic compound of furfural was attained. The flat band potential offered the possibility of reduction of dissolved O2 to O2.- in the conduction band while the trapping experiment identified the (O2.-)is the main radical species followed by h+ for the photodegradation. In-BiOBrI-0.4 had an excellent photocatalytic degradation activity which could be due to the synergetic effect between metal ion doping and solid solution formation. It further promotes visible light-harvesting ability and photoinduced charge carrier separation efficiency. The order of the reaction rate was determined and the mechanism was proposed. This work can lay a base for the design of effective photocatalyst toward environmental remediation.
Asunto(s)
Bismuto/química , Colorantes/análisis , Contaminantes Ambientales/análisis , Restauración y Remediación Ambiental/métodos , Indio/química , Compuestos de Yodo/química , Nanoestructuras/química , Fotólisis , Compuestos Azo/análisis , Catálisis , Luz , Azul de Metileno/análisis , Rodaminas/análisis , Propiedades de Superficie , TemperaturaAsunto(s)
Edema Encefálico/inducido químicamente , Medios de Contraste/efectos adversos , Angiografía Coronaria , Compuestos de Yodo/efectos adversos , Anciano , Edema Encefálico/diagnóstico por imagen , Medios de Contraste/química , Diagnóstico Diferencial , Stents Liberadores de Fármacos , Femenino , Humanos , Infarto de la Arteria Cerebral Media/diagnóstico , Compuestos de Yodo/química , Infarto del Miocardio/complicaciones , Infarto del Miocardio/diagnóstico por imagen , Infarto del Miocardio/terapia , Neuroimagen , Examen Neurológico , Concentración Osmolar , Intervención Coronaria Percutánea , Hemorragia Subaracnoidea/diagnóstico , Tomografía Computarizada por Rayos XRESUMEN
In a significant breakthrough from classical molecular (i.e., nonpolymeric) iodonium salts in light-induced photochemistry, the synthesis and use of new safer polymeric iodonium salts are reported here. They are shown to be involved in charge transfer complexes (CTCs) while in interaction with a safe amino acid derivative (N-phenylglycine). Also, this study demonstrates i) the formation of CTCs between the iodonium (acceptor) and an aryl/alkyl amine (donor) through UV-vis measurements of the monomer, ii) the formation of radicals in electron spin resonance spin trapping experiments when the CTCs are irradiated by visible light (405 nm), and iii) their efficiency as a photoinitiator to polymerize three different acrylic monomers under LED irradiation at 405 nm under air and their application to 3D resolved laser writing of thick samples (3 mm). High reactivity for polymeric iodonium salts comparable with molecular ones is exhibited with the advantage of potential lower migration. To the best of the authors' knowledge, this is the first reported instance of polymeric iodonium salts acting as polymerization initiators.
Asunto(s)
Radicales Libres/química , Compuestos de Yodo/química , Polimerizacion/efectos de la radiación , Polímeros/química , Sales (Química)/química , Glicina/análogos & derivados , Glicina/química , Luz , Procesos Fotoquímicos , Polietilenglicoles/química , Polímeros/síntesis química , Ácidos Polimetacrílicos/química , Poliestirenos/químicaRESUMEN
An efficient and simple protocol for the synthesis of trifluoromethylated quinazolines has been described by I2-/KI-promoted oxidative C(sp3)-C(sp2) bond under the optimal oxidative cyclization reaction conditions. The required 2,2,2-trifluoro-N-benzyl-N'-arylacetimidamides are readily prepared from the corresponding acetimidoyl chlorides and benzylamines under a nucleophilic substitution reaction in the form of in situ. The merits of this protocol are the use of inexpensive molecular iodine, metal-free oxidative coupling and good to excellent yields.
Asunto(s)
Compuestos de Yodo/química , Yodo/química , Yoduro de Potasio/química , Quinazolinas/síntesis química , Catálisis , Ciclización , Modelos Moleculares , Estructura MolecularRESUMEN
Iodinated contrast media (ICM) are found at considerably higher concentrations than any other pharmaceutical in waste water, surface water and bank filtrate. While the compounds are persistent to deiodination in aerobic environments, field data from bank filtration transects have demonstrated a partial deiodination in reducing soil-water environments. In a previous lab study, we have shown that this reductive deiodination is abiotically catalyzed by (free) corrinoids. To achieve a better understanding of the incomplete deiodination in the environment, we now investigated the reaction kinetics based on the decrease of the iodinated compound, the formation of deiodinated transformation products and the iodide release. The deiodination follows first-order kinetics and consists of three partial reactions for the release of three iodine atoms. The deiodination rate decreased with decreasing iodination degree with the deiodination rate constants k1â¯>â¯k2â¯>â¯k3. In contrast to the ICM, 2,4,6- and 2,3,5-triiodobenzoic acid, 5-amino-2,4,6-triiodoisophthalic acid and monoiodobenzoic acids did not show a complete deiodination under the same test conditions. Our results show that the deiodination strongly depends on the substitution pattern of the bound iodine atoms as well as on adjacent functional groups. Iodine atoms in ortho-position to another iodine atom or a carboxyl group were released more easily while an amino group in ortho-position inhibited the deiodination. Tests in tap water in the presence of B12 showed a much slower deiodination than in ultrapure water, most likely caused by competitive electron acceptors in the water matrix.
Asunto(s)
Medios de Contraste/química , Compuestos de Yodo/química , Aguas Residuales/química , Contaminantes Químicos del Agua/química , Catálisis , Corrinoides , Filtración , Halogenación , Yodo , Cinética , Oxidantes , Eliminación de Residuos Líquidos/métodos , Rayos XRESUMEN
Despite their broad utility, the synthesis of ortho-quinones remains a significant challenge, in particular, access to electron-deficient derivatives remains an unsolved problem. Reported here is the first general method for the synthesis of electron-deficient ortho-quinones by direct oxidation of phenols. The reaction is enabled by a novel bidentate nitrogen-ligated iodine(V) reagent, a previously unexplored class of compounds which we have termed Bi(N)-HVIs. The reaction is extremely general and proceeds with excellent regioselectivity for the ortho over para isomer. Functionalization of the ortho-quinone products was examined, resulting in a facile one-pot synthesis of catechols, as well as the incorporation of a variety of heteroatom nucleophiles. This method represents the first synthetic application of Bi(N)-HVIs and demonstrates their potential as a platform for the further development of highly reactive, but also highly tunable, I(V) reagents.
Asunto(s)
Catecoles/química , Electrones , Compuestos de Yodo/química , Nitrógeno/química , Fenoles/química , Quinonas/química , Estructura Molecular , Oxidación-ReducciónRESUMEN
The reactivity of hydrogen peroxide and catalytic hydroiodic acid toward 3,6-dimethoxy-2-(cycloamino)anilines is tunable to give ring-fused benzimidazoles or 1,4,6,9-tetramethoxyphenazine in high yield. Mechanisms via a detected nitroso-intermediate are proposed for oxidative cyclization and the unexpected intermolecular displacement of the oxazine. An aqueous solution of molecular iodine is capable of the same transformations. Oxidative demethylation gave targeted benzimidazolequinones, including without cleavage of the incorporated oxetane.
Asunto(s)
Antineoplásicos/química , Bencimidazoles/química , Descubrimiento de Drogas , Éteres Cíclicos/química , Morfolinas/química , Fenazinas/química , Quinonas/química , Ácidos/química , Antineoplásicos/síntesis química , Bencimidazoles/síntesis química , Catálisis , Ciclización , Peróxido de Hidrógeno/química , Compuestos de Yodo/química , Estructura Molecular , Oxidación-Reducción , Fenazinas/síntesis química , Quinonas/síntesis químicaRESUMEN
The antimicrobial properties of graphene-based membranes such as single-layer graphene oxide (GO) and modified graphene oxide (rGO) on top of cellulose ester membrane are reported in this study. rGO membranes are made from GO by hydriodic acid (HI) vapor treatment. The antibacterial properties are tested after 3 h contact time with selected model bacteria. Complete bacterial cell inactivation is found only after contact with rGO membranes, while no significant bacterial inactivation is found for the control i) GO membrane, ii) the mixed cellulose ester support, and the iii) rGO membrane after additional washing that removes the remaining HI. This indicates that the antimicrobial effect is neither caused by the graphene nor the membrane support. The antimicrobial effect is found to be conclusively linked to the HI eliminating microbial growth, at concentrations from 0.005%. These findings emphasize the importance of caution in the reporting of antimicrobial properties of graphene-based surfaces.
Asunto(s)
Ácidos/química , Antibacterianos/farmacología , Grafito/farmacología , Compuestos de Yodo/química , Membranas Artificiales , Bacterias/efectos de los fármacos , Pruebas de Sensibilidad Microbiana , Viabilidad Microbiana/efectos de los fármacos , Oxidación-Reducción , Espectroscopía Infrarroja por Transformada de Fourier , Difracción de Rayos XRESUMEN
Efficient charge transport has been observed in iodine-doped, iodide-based room-temperature ionic liquids, yielding high ionic conductivity. To elucidate preferred mechanistic pathways for the iodide ( I - )-to-triiodide ( I 3 - ) exchange reactions, we have performed 10 ns reactive molecular-dynamics calculations in the liquid state for 1-butyl-3-methylimidazolium iodide ([BMIM][I]) at 450 to 750 K. Energy-barrier distributions for the iodine-swapping process were determined as a function of temperature, employing a charge-reassignment scheme drawn in part from electronic-structure calculations. Bond-exchange events were observed with rate-determining energy barriers ranging from ~0.19 to 0.23 ± 0.06 eV at 750 and 450 K, respectively, with an approximately Arrhenius temperature dependence for iodine self-diffusivity and reaction kinetics, although diffusion dominates/limits the bond-exchange events. This charge transfer is not dissimilar in energetics to those in solid-state superionic conductors.
Asunto(s)
Compuestos de Yodo/química , Líquidos Iónicos/química , Imidazoles/química , CinéticaRESUMEN
Proton-coupled electron transfer (PCET) is an important chemical and biological phenomenon. It is attractive as an on-off switching mechanism for redox-active synthetic systems but has not been extensively exploited for this purpose. Here we report a core-modified planar weakly antiaromatic/nonaromatic octaphyrin, namely, a [32]octaphyrin(1.0.1.0.1.0.1.0) (1) derived from rigid naphthobipyrrole and dithienothiophene (DTT) precursors, that undergoes proton-coupled two-electron reduction to produce its aromatic congener in the presence of HCl and other hydrogen halides. Evidence for the production of a [4 n + 1] π-electron intermediate radical state is seen in the presence of trifluoroacetic acid. Electrochemical analyses provide support for the notion that protonation causes a dramatic anodic shift in the reduction potentials of octaphyrin 1, thereby facilitating electron transfer from halide anions (viz. I-, Br-, and, Cl-). Electron-rich molecules, such as tetrathiafulvene (TTF), phenothiazine (PTZ), and catechol, were also found to induce PCET in the case of 1. Both the oxidized and two-electron reduced forms of 1 were characterized by X-ray diffraction analyses in the solid state and in solution via spectroscopic means.
Asunto(s)
Compuestos Heterocíclicos de 4 o más Anillos/química , Compuestos Macrocíclicos/química , Protones , Ácidos/química , Compuestos Heterocíclicos de 4 o más Anillos/síntesis química , Ácido Bromhídrico/química , Ácido Clorhídrico/química , Compuestos de Yodo/química , Compuestos Macrocíclicos/síntesis química , Estructura Molecular , Oxidación-ReducciónRESUMEN
Toxic and odorous iodinated disinfection byproducts (I-DBPs) could form in the chemical oxidation of iodine-containing water. A critical step for controlling the hazardous I-DBPs is to convert the iodine species into stable and harmless iodate (IO3-) while inhibiting the accumulation of highly reactive hypoiodous acid (HOI). Herein, the oxidation of I- and HOI with ferrate was investigated, and the formation profile of HOI was determined based on 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) coloring method through a stopped-flow spectrophotometer. The second-order rate constants (kapp) of ferrate with HOI decreased from 1.6â¯×â¯105â¯M-1s-1 to 8.3â¯×â¯102â¯M-1s-1 as the solution pH varied from 5.3 to 10.3, which were 7.5, 7.2 and 13.8 times higher than that of ferrate with I- at pH 6.0, 7.0 and 8.0, respectively. Compared with other oxidants such as ozone, hypochlorous acid, chloramine and potassium permanganate, ferrate would swiftly oxidize HOI formed in the I- oxidation process. For the ferrate oxidation of I-containing water, HOI was swiftly oxidized to IO3- from pH 5.0 to 9.0. Phosphate buffer promoted the oxidation of I- while inhibited the oxidation of HOI with ferrate. When 5 mgC/L of humic acids (HA) existed in the solution, no formation of iodoform and monoiodoacetic acid (MIAA) was observed in the oxidation of iodide (20⯵M) with ferrate (from 10⯵M to 80⯵M). These results suggested that ferrate oxidation could be an effective method for the control of I-DBPs in iodine-containing water treatment.
Asunto(s)
Hidrocarburos Yodados/química , Yoduros/química , Compuestos de Yodo/química , Purificación del Agua/métodos , Desinfección/métodos , Halogenación , Sustancias Húmicas , Concentración de Iones de Hidrógeno , Yodatos/química , Ácido Yodoacético/química , Hierro/química , Oxidantes/química , Oxidación-Reducción , Ozono , Permanganato de PotasioRESUMEN
Lactoperoxidase (LPO) is an enzyme found in several exocrine secretions including the airway surface liquid producing antimicrobial substances from mainly halide and pseudohalide substrates. Although the innate immune function of LPO has been documented against several microbes, a detailed characterization of its mechanism of action against influenza viruses is still missing. Our aim was to study the antiviral effect and substrate specificity of LPO to inactivate influenza viruses using a cell-free experimental system. Inactivation of different influenza virus strains was measured in vitro system containing LPO, its substrates, thiocyanate (SCN-) or iodide (I-), and the hydrogen peroxide (H2O2)-producing system, glucose and glucose oxidase (GO). Physiologically relevant concentrations of the components of the LPO/H2O2/(SCN-/I-) antimicrobial system were exposed to twelve different strains of influenza A and B viruses in vitro and viral inactivation was assessed by determining plaque-forming units of non-inactivated viruses using Madin-Darby canine kidney cells (MDCK) cells. Our data show that LPO is capable of inactivating all influenza virus strains tested: H1N1, H1N2 and H3N2 influenza A viruses (IAV) and influenza B viruses (IBV) of both, Yamagata and Victoria lineages. The extent of viral inactivation, however, varied among the strains and was in part dependent on the LPO substrate. Inactivation of H1N1 and H1N2 viruses by LPO showed no substrate preference, whereas H3N2 influenza strains were inactivated significantly more efficiently when iodide, not thiocyanate, was the LPO substrate. Although LPO-mediated inactivation of the influenza B strains tested was strain-dependent, it showed slight preference towards thiocyanate as the substrate. The results presented here show that the LPO/H2O2/(SCN-/I-) cell-free, in vitro experimental system is a functional tool to study the specificity, efficiency and the molecular mechanism of action of influenza inactivation by LPO. These studies tested the hypothesis that influenza strains are all susceptible to the LPO-based antiviral system but exhibit differences in their substrate specificities. We propose that a LPO-based antiviral system is an important contributor to anti-influenza virus defense of the airways.
Asunto(s)
Antivirales/farmacología , Gripe Humana/tratamiento farmacológico , Lactoperoxidasa/química , Orthomyxoviridae/efectos de los fármacos , Animales , Antivirales/química , Sistema Libre de Células/efectos de los fármacos , Perros , Humanos , Subtipo H1N1 del Virus de la Influenza A/efectos de los fármacos , Subtipo H1N1 del Virus de la Influenza A/patogenicidad , Subtipo H3N2 del Virus de la Influenza A/efectos de los fármacos , Subtipo H3N2 del Virus de la Influenza A/patogenicidad , Virus de la Influenza B/efectos de los fármacos , Virus de la Influenza B/patogenicidad , Gripe Humana/virología , Compuestos de Yodo/química , Compuestos de Yodo/metabolismo , Compuestos de Yodo/farmacología , Lactoperoxidasa/metabolismo , Células de Riñón Canino Madin Darby , Orthomyxoviridae/patogenicidad , Especificidad por Sustrato , Tiocianatos/química , Tiocianatos/metabolismo , Tiocianatos/farmacologíaRESUMEN
This work investigated impacts of iodide (I-) on the transformation of the widely used phenolic preservative methylparaben (MeP) as well as 11 other phenolic compounds by potassium permanganate (KMnO4). It was found that KMnO4 showed a low reactivity towards MeP in the absence of I- with apparent second-order rate constants (kapp) ranging from 0.065⯱â¯0.0071 to 1.0⯱â¯0.1â¯M-1s-1 over the pH range of 5-9. The presence of I- remarkably enhanced the transformation rates of MeP by KMnO4 via the contribution of hypoiodous acid (HOI) in situ formed, which displayed several orders of magnitude higher reactivity towards MeP than KMnO4. This enhancing effect of I- was greatly influenced by solution conditions (e.g., I- or KMnO4 concentration or pH), which could be well simulated by a kinetic model involving competition reactions (i.e., KMnO4 with I-, KMnO4 with MeP, HOI with KMnO4, and HOI with MeP). Similar enhancing effect of I- on the transformation kinetics of 5 other selected phenols (i.e., p-hydroxybenzoic acid, phenol, and bromophenols) at pH 7 was also observed, but not in the cases of bisphenol A, triclosan, 4-n-nonylphenol, and cresols. This discrepancy could be well explained by the relative reactivity of KMnO4 towards phenols vs I-. Liquid chromatography-tandem mass spectrometry analysis showed that iodinated aromatic products and/or iodinated quinone-like product were generated in the cases where I- enhancing effect was observed. Evolution of iodinated aromatic products generated from MeP (10⯵M) treated by KMnO4 (50-150⯵M) in the presence of I- (5-15⯵M) suggested that higher I- or moderate KMnO4 concentration or neutral pH promoted their formation. A similar enhancing effect of I- (1⯵M) on the transformation of MeP (1⯵M) by KMnO4 (12.6⯵M) and formation of iodinated aromatic products were also observed in natural water. This work demonstrates an important role of I- in the transformation kinetics and product formation of phenolic compounds by KMnO4, which has great implications for future applications of KMnO4 in treatment of I--containing water.
Asunto(s)
Yoduros/química , Parabenos/química , Fenoles/química , Compuestos de Bencidrilo/química , Halogenación , Concentración de Iones de Hidrógeno , Compuestos de Yodo/química , Cinética , Modelos Químicos , Permanganato de Potasio/química , Triclosán/química , Contaminantes Químicos del Agua/química , Purificación del Agua/métodosRESUMEN
The properties of halogen bonds (XBs) in solid-state I2X- and I4X- materials (where X = Cl, Br) are explored using donor K-edge X-ray absorption spectroscopy (XAS) to experimentally determine the degree of charge transfer in such XB interactions. The degree of covalency in these bonds is substantial, even in cases where significantly weaker secondary interactions are observed. These data, in concert with previous work in this area, suggests that certain halogen bonds have covalent contributions to bonding that are similar to, and even exceed, those observed in transition metal coordinate bonds. For this reason, we suggest that XB interactions of this type be denoted in a similar way to coordination bonds (X â Y) as opposed to using a representation that is the same as for significantly less covalent hydrogen bonds (XY).
Asunto(s)
Cloruros/química , Complejos de Coordinación/química , Halógenos/química , Compuestos de Yodo/química , Potasio/química , Espectroscopía de Absorción de Rayos X/métodos , Cristalografía por Rayos X , Conductividad Eléctrica , Enlace de Hidrógeno , Modelos MolecularesRESUMEN
Photochemical halogenation of dissolved organic matter (DOM) may represent an important abiotic process for the formation of natural organobromine compounds (OBCs) and natural organoiodine compounds (OICs) within surface waters. Here we report the enhanced formation of OBCs and OICs by photohalogenating DOM in freshwater and seawater, as well as the noticeable difference in the distribution and composition pattern of newly formed OBCs and OICs. By using negative ion electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry, various OBCs and OICs were identified during the photohalogenation processes in sunlit waters. The respective number of OBCs and OICs formed in artificial seawater (ASW) under light radiation was higher than that in artificial freshwater (AFW), suggesting a possible role of the mixed reactive halogen species. OBCs were formed mainly via substitution reactions and addition reactions accompanied by other reactions and distributed into three classes: unsaturated hydrocarbons with relatively low oxygen content, unsaturated aliphatic compounds, and saturated fatty acids and carbohydrates with relatively high hydrogen content. Unlike the OBCs, OICs were located primarily in the region of carboxylic-rich alicyclic molecules composed of esterified phenolic, carboxylated, and fused alicyclic structures and were generated mainly through electrophilic substitution of the aromatic proton. Our findings call for further investigation on the exact structure and toxicity of the OBCs and OICs generated in the natural environment.
Asunto(s)
Compuestos de Bromina/química , Compuestos de Yodo/química , Espectrometría de Masas , Agua de Mar/química , Agua Dulce , Halogenación , Espectrometría de Masa por Ionización de ElectrosprayRESUMEN
The kinetics for the reactions of hypoiodous acid (HOI) with various phenols (phenol, 4-nitrophenol, 4-hydroxybenzoic acid), 3-oxopentanedioic acid (3-OPA) and flavone were investigated in the pH range of 6.0-11.0. The apparent second order rate constants for the reactions of HOI with phenolic compounds, 3-OPA, flavone and citric acid at pH 8.0 are 10-107 M-1s-1, (4.0 ± 0.3) × 103 M-1s-1, (2.5 ± 0.2) × 103 M-1s-1 and <1 M-1s-1, respectively. The effect of buffer type and concentration was investigated with acetate, phosphate and borate. All tested buffers promote the HOI reactions with phenols. The percentage of iodine incorporation for various (hydroxyl)phenolic compounds and two NOM extracts ranges from 5% to 98%, indicating that electrophilic aromatic substitution and/or electron transfer can occur. The extent of these reactions depends on the number and relative position of the hydroxyl moieties on the phenolic compounds. Iodoform formation rates increase with increasing pH and iodoform yields increase from 9% to 67% for pH 6.0-10.0 for the HOI/3-OPA reactions. In the permanganate/HOI/3-OPA and permanganate/iodide/3-OPA system at pH < 8.0, iodoform formation is elevated compared to the HOI/3-OPA system in absence of permanganate. For pH > 8.0, in presence of permanganate, iodoform formation is significantly inhibited and iodate formation enhanced, which is due to a faster permanganate-mediated HOI disproportionation to iodate compared to the iodination process. The production of reactive iodine in real waters containing iodide in contact with permanganate may lead to the formation of iodinated organic compounds.
Asunto(s)
Compuestos de Yodo/química , Compuestos de Manganeso/química , Óxidos/química , Purificación del Agua , Hidrocarburos Yodados , Concentración de Iones de Hidrógeno , Cinética , Oxidación-Reducción , Contaminantes Químicos del AguaRESUMEN
Iodinated pharmaceuticals, thyroxine (a thyroid hormone) and diatrizoate (an iodinated X-ray contrast medium), are among the most prescribed active pharmaceutical ingredients. Both of them have been reported to potentially disrupt thyroid homeostasis even at very low concentrations. In this study, UV-254 nm-based photolysis and photochemical processes, i.e., UV only, UV/H2O2, and UV/S2O82-, were evaluated for the destruction of these two pharmaceuticals. Approximately 40% of 0.5µM thyroxine or diatrizoate was degraded through direct photolysis at UV fluence of 160mJcm-2, probably resulting from the photosensitive cleavage of C-I bonds. While the addition of H2O2 only accelerated the degradation efficiency to a low degree, the destruction rates of both chemicals were significantly enhanced in the UV/S2O82- system, suggesting the potential vulnerability of the iodinated chemicals toward UV/S2O82- treatment. Such efficient destruction also occurred in the presence of radical scavengers when biologically treated wastewater samples were used as reaction matrices. The effects of initial oxidant concentrations, solution pH, as well as the presence of natural organic matter (humic acid or fulvic acid) and alkalinity were also investigated in this study. These results provide insights for the removal of iodinated pharmaceuticals in water and/or wastewater using UV-based photochemical processes.