Journal articles: 'Halogeny'

1

Tang, Hai-Tao, Jun-Song Jia, and Ying-Ming Pan. "Halogen-mediated electrochemical organic synthesis." Organic & Biomolecular Chemistry 18, no. 28 (2020): 5315–33. http://dx.doi.org/10.1039/d0ob01008a.

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Biester, H., D. Selimović, S. Hemmerich, and M. Petri. "Halogens in porewater of peat bogs – the role of peat decomposition and dissolved organic matter." Biogeosciences Discussions 2, no. 5 (September 20, 2005): 1457–86. http://dx.doi.org/10.5194/bgd-2-1457-2005.

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Abstract. Peatlands are one of the largest active terrestrial reservoirs of halogens. Formation of organo-halogens is a key process for the retention of halogens by organic matter and halogen enrichment in peat is strongly influenced by climatically controlled humification processes. However, little is known about release and transport of halogens in peat bogs. In this study we investigated the release of halogens from peat in three peat bogs located in the Magellanic Moorlands, southern Chile. Peat porewaters were collected using a sipping technique, which allows in situ sampling down to a depth of more than 6 m. Halogens and halogen species in porewater were determined by ion-chromatography (IC) (chlorine) and IC-ICP-MS (bromine and iodine). Results show that halogen concentrations in porewater are 15–30 times higher than in rainwater suggesting that their release from peat during diagenesis is the major source of halogens in porewater. Mean concentrations of chlorine, bromine and iodine in porewater were 7–15 mg l−1, 56–123μg l−1, and 10–20μg l−1, which correspond to mean proportions of 10–15%, 1–2.3% and 0.5–2.2% of total concentrations in peat, respectively. Organo-bromine and organoiodine were predominant in porewaters, whereas the release of organo-chlorine compounds from peat appears to be of minor importance. Results show that the release of bromine and iodine from peat depend on the degree of peat degradation, whereas this relationship is weak for chlorine. Relatively higher release of bromine and iodine was observed in less degraded peat sections, where the release of dissolved organic carbon (DOC) was also the most intensive. Here, proportions of released iodine and bromine follow proportions of released dissolved organic matter (DOM) indicating that the release of halogenated DOM is the predominant process of iodine and bromine release from peat.

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Grineva, O. V. "Intermolecular halogen...halogen contacts in crystals with heteroatomic halogens." Acta Crystallographica Section A Foundations of Crystallography 68, a1 (August 7, 2012): s67. http://dx.doi.org/10.1107/s0108767312098716.

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Biester, H., D. Selimović, S. Hemmerich, and M. Petri. "Halogens in pore water of peat bogs – the role of peat decomposition and dissolved organic matter." Biogeosciences 3, no. 1 (January 27, 2006): 53–64. http://dx.doi.org/10.5194/bg-3-53-2006.

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Abstract. Halogens are strongly enriched in peat and peatlands and such they are one of their largest active terrestrial reservoir. The enrichment of halogens in peat is mainly attributed to the formation of organohalogens and climatically controlled humification processes. However, little is known about release of halogens from the peat substrate and the distribution of halogens in the peat pore water. In this study we have investigated the distribution of chlorine, bromine and iodine in pore water of three pristine peat bogs located in the Magellanic Moorlands, southern Chile. Peat pore waters were collected using a sipping technique, which allows in situ sampling down to a depth greater than 6m. Halogens and halogen species in pore water were determined by ion-chromatography (IC) (chlorine) and IC-ICP-MS (bromine and iodine). Results show that halogen concentrations in pore water are 15–30 times higher than in rainwater. Mean concentrations of chlorine, bromine and iodine in pore water were 7–15 mg l−1, 56–123 μg l−1, and 10–20 μg l−1, which correspond to mean proportions of 10–15%, 1–2.3% and 0.5–2.2% of total concentrations in peat, respectively. Organobromine and organoiodine were the predominant species in pore waters, whereas chlorine in pore water was mostly chloride. Advection and diffusion of halogens were found to be generally low and halogen concentrations appear to reflect release from the peat substrate. Release of bromine and iodine from peat depend on the degree of peat degradation, whereas this relationship is weak for chlorine. Relatively higher release of bromine and iodine was observed in less degraded peat sections, where the release of dissolved organic carbon (DOC) was also the most intensive. It has been concluded that the release of halogenated dissolved organic matter (DOM) is the predominant mechanism of iodine and bromine release from peat.

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Kia, Reza, Soheil Mahmoudi, and Paul R. Raithby. "New rhenium-tricarbonyl complexes bearing halogen-substituted bidentate ligands: structural, computational and Hirshfeld surfaces studies." CrystEngComm 21, no. 1 (2019): 77–93. http://dx.doi.org/10.1039/c8ce01860j.

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The intermolecular interactions in a series of new complexes Re(CO)₃(N,N)X (N,N is a halogen substituted bidentate N–N donor and X is Cl or Br) have been studied crystallographically and computationally. Metal-bound halogens are more effective than carbon-bound halogens in forming significant intermolecular interactions.

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Parlak, Cemal, Mahir Tursun, Chandraju Sadolalu Chidan Kumar, Duygu Bilge, Nadide Kazanci, Lydia Rhyman, and Ponnadurai Ramasami. "Halogen and solvent effects on the conformational, vibrational and electronic properties of 1,4-diformylpiperazine: A combined experimental and DFT study." Journal of Theoretical and Computational Chemistry 14, no. 07 (November 2015): 1550050. http://dx.doi.org/10.1142/s0219633615500509.

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The molecular structure and properties of 1,4-diformylpiperazine (1,4-dfp, C6H[Formula: see text]N2O2) were investigated by Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy and density functional theory (DFT). The Becke-3-Lee–Yang–Parr (B3LYP) functional was used with the 6-31[Formula: see text]G(d,p) basis set. Total energy distribution (TED) analysis of normal modes was performed to identify characteristic frequencies by the scaled quantum mechanical (SQM) method. Halogeno-analogs of 1,4-dfp were studied to understand the halogen effect. Computations were focused on five conformational isomers of the compounds in the gas phase and in solutions. The computed and experimental frequencies of the C[Formula: see text]O stretching vibration of 1,4-dfp were correlated with the empirical solvent parameters such as the Kirkwood–Bauer–Magat (KBM) equation, the solvent acceptor number (AN), Swain parameters and linear solvation energy relationships (LSER). The electronic properties of the compounds were also examined. The findings from the present work may be useful to understand systems involving the halogens and conformational changes analogous to the compounds investigated.

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Puttreddy, Rakesh, Carolina von Essen, Anssi Peuronen, Manu Lahtinen, and Kari Rissanen. "Halogen bonds in 2,5-dihalopyridine-copper(ii) chloride complexes." CrystEngComm 20, no. 14 (2018): 1954–59. http://dx.doi.org/10.1039/c8ce00209f.

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In the (2,5-dihalopyridine)₂·CuCl₂ complexes varying the C5-position halogens affects the halogen bonding properties so that the C5–X5⋯Cl–Cu halogen bonds follow the order F5 < Cl5 < Br5 < I5 when the substituent at 2-position is chlorine and Cl5 < Br5 < I5 when it is bromine.

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8

Scheiner, Steve. "On the capability of metal–halogen groups to participate in halogen bonds." CrystEngComm 21, no. 18 (2019): 2875–83. http://dx.doi.org/10.1039/c9ce00496c.

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9

Cavallo, Gabriella, Jane S. Murray, Peter Politzer, Tullio Pilati, Maurizio Ursini, and Giuseppe Resnati. "Halogen bonding in hypervalent iodine and bromine derivatives: halonium salts." IUCrJ 4, no. 4 (May 10, 2017): 411–19. http://dx.doi.org/10.1107/s2052252517004262.

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Halogen bonds have been identified in a series of ionic compounds involving bromonium and iodonium cations and several different anions, some also containing hypervalent atoms. The hypervalent bromine and iodine atoms in the examined compounds are found to have positive σ-holes on the extensions of their covalent bonds, while the hypervalent atoms in the anions have negative σ-holes. The positive σ-holes on the halogens of the studied halonium salts determine the linearity of the short contacts between the halogen and neutral or anionic electron donors, as usual in halogen bonds.

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10

Sherwen, Tomás, Mat J. Evans, Lucy J. Carpenter, Johan A. Schmidt, and Loretta J. Mickley. "Halogen chemistry reduces tropospheric O3 radiative forcing." Atmospheric Chemistry and Physics 17, no. 2 (January 31, 2017): 1557–69. http://dx.doi.org/10.5194/acp-17-1557-2017.

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Abstract. Tropospheric ozone (O3) is a global warming gas, but the lack of a firm observational record since the preindustrial period means that estimates of its radiative forcing (RFTO3) rely on model calculations. Recent observational evidence shows that halogens are pervasive in the troposphere and need to be represented in chemistry-transport models for an accurate simulation of present-day O3. Using the GEOS-Chem model we show that tropospheric halogen chemistry is likely more active in the present day than in the preindustrial. This is due to increased oceanic iodine emissions driven by increased surface O3, higher anthropogenic emissions of bromo-carbons, and an increased flux of bromine from the stratosphere. We calculate preindustrial to present-day increases in the tropospheric O3 burden of 113 Tg without halogens but only 90 Tg with, leading to a reduction in RFTO3 from 0.43 to 0.35 Wm−2. We attribute ∼ 50 % of this reduction to increased bromine flux from the stratosphere, ∼ 35 % to the ocean–atmosphere iodine feedback, and ∼ 15 % to increased tropospheric sources of anthropogenic halogens. This reduction of tropospheric O3 radiative forcing due to halogens (0.087 Wm−2) is greater than that from the radiative forcing of stratospheric O3 (∼ 0.05 Wm−2). Estimates of RFTO3 that fail to consider halogen chemistry are likely overestimates (∼ 25 %).

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11

von Essen, Carolina, Kari Rissanen, and Rakesh Puttreddy. "Halogen Bonds in 2,5-Dihalopyridine-Copper(I) Halide Coordination Polymers." Materials 12, no. 20 (October 11, 2019): 3305. http://dx.doi.org/10.3390/ma12203305.

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Two series of 2,5-dihalopyridine-Cu(I)A (A = I, Br) complexes based on 2-X-5-iodopyridine and 2-X-5-bromopyridine (X = F, Cl, Br and I) are characterized by using single-crystal X-ray diffraction analysis to examine the nature of C2−X2···A–Cu and C5−X5···A–Cu halogen bonds. The reaction of the 2,5-dihalopyridines and Cu(I) salts allows the synthesis of eight 1-D coordination polymers and a discrete structure. The resulting Cu(I)-complexes are linked by C−X···A–Cu halogen bonds forming 3-D supramolecular networks. The C−X···A–Cu halogen bonds formed between halopyridine ligands and copper(I)-bound halide ions are stronger than C−X···X’–C interactions between two 2,5-dihalopyridine ligands. The C5−I5···I–Cu and C5−Br5···Br–Cu halogens bonds are shorter for C2-fluorine than C2-chlorine due to the greater electron-withdrawing power of fluorine. In 2,5-diiodopyridine-Cu(I)Br complex, the shorter C2−I2···Br–Cu [3.473(5) Å] distances are due to the combined polarization of C2-iodine by C2−I2···Cu interactions and para-electronic effects offered by the C5-iodine, whilst the long halogen bond contacts for C5−I5···Br–Cu [3.537(5) Å] are indicative that C2-iodine has a less para-electronic influence on the C5-iodine. In 2-fluoro-5-X-pyridine-Cu(I) complexes, the C2-fluorine is halogen bond passive, while the other C2-halogens in 2,5-dihalopyridine-Cu(I), including C2-chlorine, participate in halogen bonding interactions.

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12

Gil, Aleksander, Zbigniew Żurek, Adam Stawiarski, and Jarosław Dąbek. "Improvement of Oxidation Resistance of TiAl-Nb Alloy by Dipping in F-Containing Resin." Advanced Materials Research 347-353 (October 2011): 3514–17. http://dx.doi.org/10.4028/www.scientific.net/amr.347-353.3514.

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Surface treatment of TiAl alloys by the small amounts of halogens leads to the formation of the protective alumina scale. The halogens can be applied by ion techniques as well as by spraying or dipping with halogen-containing compounds. In this work the results of the oxidation in air of a Ti-47Al-6Nb alloy dipped in a fluorine-containing resin were presented. The thermal cycling runs were carried out in the temperature 900°C.

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13

Scattolin, Thomas, Fabiano Visentin, Claudio Santo, Valerio Bertolasi, and Luciano Canovese. "The unexpected case of reactions of halogens and interhalogens with halide substituted Pd(ii) σ-butadienyl complexes." Dalton Transactions 45, no. 28 (2016): 11560–67. http://dx.doi.org/10.1039/c6dt01964a.

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Palladium σ-butadienyl derivatives react with halogens and interhalogens, under mild experimental conditions, to induce the substitution of the halogen to coordinated palladium and to the terminal butadienyl carbon without extrusion of the butadienyl fragment.

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14

Simpson, W. R., R. von Glasow, K. Riedel, P. Anderson, P. Ariya, J. Bottenheim, J. Burrows, et al. "Halogens and their role in polar boundary-layer ozone depletion." Atmospheric Chemistry and Physics 7, no. 16 (August 22, 2007): 4375–418. http://dx.doi.org/10.5194/acp-7-4375-2007.

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Abstract. During springtime in the polar regions, unique photochemistry converts inert halide salt ions (e.g. Br−) into reactive halogen species (e.g. Br atoms and BrO) that deplete ozone in the boundary layer to near zero levels. Since their discovery in the late 1980s, research on ozone depletion events (ODEs) has made great advances; however many key processes remain poorly understood. In this article we review the history, chemistry, dependence on environmental conditions, and impacts of ODEs. This research has shown the central role of bromine photochemistry, but how salts are transported from the ocean and are oxidized to become reactive halogen species in the air is still not fully understood. Halogens other than bromine (chlorine and iodine) are also activated through incompletely understood mechanisms that are probably coupled to bromine chemistry. The main consequence of halogen activation is chemical destruction of ozone, which removes the primary precursor of atmospheric oxidation, and generation of reactive halogen atoms/oxides that become the primary oxidizing species. The different reactivity of halogens as compared to OH and ozone has broad impacts on atmospheric chemistry, including near complete removal and deposition of mercury, alteration of oxidation fates for organic gases, and export of bromine into the free troposphere. Recent changes in the climate of the Arctic and state of the Arctic sea ice cover are likely to have strong effects on halogen activation and ODEs; however, more research is needed to make meaningful predictions of these changes.

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15

Simpson, W. R., R. von Glasow, K. Riedel, P. Anderson, P. Ariya, J. Bottenheim, J. Burrows, et al. "Halogens and their role in polar boundary-layer ozone depletion." Atmospheric Chemistry and Physics Discussions 7, no. 2 (March 29, 2007): 4285–403. http://dx.doi.org/10.5194/acpd-7-4285-2007.

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Abstract. During springtime in the polar regions, unique photochemistry converts inert halide salts ions (e.g. Br−) into reactive halogen species (e.g. Br atoms and BrO) that deplete ozone in the boundary layer to near zero levels. Since their discovery in the late 1980s, research on ozone depletion events (ODEs) has made great advances; however many key processes remain poorly understood. In this article we review the history, chemistry, dependence on environmental conditions, and impacts of ODEs. This research has shown the central role of bromine photochemistry, but how salts are transported from the ocean and are oxidized to become reactive halogen species in the air is still not fully understood. Halogens other than bromine (chlorine and iodine) are also activated through incompletely understood mechanisms that are probably coupled to bromine chemistry. The main consequence of halogen activation is chemical destruction of ozone, which removes the primary precursor of atmospheric oxidation, and generation of reactive halogen atoms/oxides that become the primary oxidizing species. The different reactivity of halogens as compared to OH and ozone has broad impacts on atmospheric chemistry, including near complete removal and deposition of mercury, alteration of oxidation fates for organic gases, and export of bromine into the free troposphere. Recent changes in the climate of the Arctic and state of the Arctic sea ice cover are likely to have strong effects on halogen activation and ODEs; however, more research is needed to make meaningful predictions of these changes.

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16

Poynder, Tiffany B., Dharmeshkumar P. Savaliya, Andrew Molino, David J. D. Wilson, and Jason L. Dutton. "Elimination of Ethene from 1,2-Diiodoethane Induced by N-Heterocyclic Carbene Halogen Bonding." Australian Journal of Chemistry 72, no. 8 (2019): 614. http://dx.doi.org/10.1071/ch19237.

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The attempted synthesis of N-heterocyclic carbene (NHC)-stabilised dicarbon (C2) fragments via nucleophilic substitution at 1,2-diiodoethane is reported. Rather than the expected SN2 pathway, clean elimination of ethene and formation of an iodoimidazolium cation was observed. The resistance towards nucleophilic substitution piqued interest, and subsequent investigation determined NHC-halogen bonding as the source. This is in contrast to reactions between NHCs and other alkyl halides, where substitution or elimination pathways are reported. A detailed theoretical study between these cases highlights the importance of iodine as a halogen bond donor compared with other halogens, and shows that NHCs are excellent halogen bond acceptors. This reactivity suggests potential for application of the halogen bonding interaction between NHCs and organic compounds.

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Simpson, W. R., D. Carlson, G. Hoenninger, T. A. Douglas, M. Sturm, D. Perovich, and U. Platt. "First-year sea-ice contact predicts bromine monoxide (BrO) levels better than potential frost flower contact." Atmospheric Chemistry and Physics Discussions 6, no. 6 (November 7, 2006): 11051–66. http://dx.doi.org/10.5194/acpd-6-11051-2006.

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Abstract. Reactive halogens are responsible for boundary-layer ozone depletion and mercury deposition in Polar Regions during springtime. To investigate the source of reactive halogens in the air arriving at Barrow, Alaska, we measured BrO, a marker of reactive halogen chemistry, and correlated its abundance with airmass histories derived from meteorological back trajectories and remotely sensed sea ice properties. The BrO is found to be positively correlated to first-year sea-ice contact (R2=0.55), and weakly negatively correlated to potential frost flower (PFF) contact (R2=0.04). These data indicate that snow contaminated with sea salts on first-year sea ice is a more probable bromine source than are frost flowers. Recent climate-driven changes in Arctic sea ice are likely to alter frost flower and first year sea ice prevalence, suggesting a significant change in reactive halogen abundance, which will alter the chemistry of the overlying Arctic atmosphere.

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18

Gil, Aleksander, Zbigniew Żurek, and Adam Stawiarski. "Oxidation of TiAl Alloys Coated by Fluorine Resin in SO₂ Containing Atmosphere." Materials Science Forum 654-656 (June 2010): 562–65. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.562.

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There are several ways to improve the oxidation resistance of TiAl alloys. One of them is alloying with elements such as Nb, Ta, W, Si, Ag, Zr or Hf. However, bulk alloying influences the mechanical properties. Surface treatment of TiAl alloys by the small amounts of halogens leads to the formation of the protective alumina scale (“halogen effect”). The halogens can be applied by ion techniques (ion implantation, plasma immersion implantation) but also by spraying or dipping with halogen-containing inorganic and organic compounds. Deposition of the fluorine-containing resin on the surface of TiAl alloys is the easiest way to achieve the best results. SO2 impurity in air significantly influences oxidation behavior of TiAl alloys. In this work the results of the oxidation of a Ti-48Al-2Cr alloy coated with a fluorine-containing resin in the synthetic air and air containing 1% SO2 were presented. The oxidation runs were carried out in the temperature range 800-1000°C.

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19

Grabowski, Sławomir J. "A–X⋯σ Interactions—Halogen Bonds with σ-Electrons as the Lewis Base Centre." Molecules 26, no. 17 (August 26, 2021): 5175. http://dx.doi.org/10.3390/molecules26175175.

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CCSD(T)/aug-cc-pVTZ//ωB97XD/aug-cc-pVTZ calculations were performed for halogen-bonded complexes. Here, the molecular hydrogen, cyclopropane, cyclobutane and cyclopentane act as Lewis base units that interact through the electrons of the H–H or C–C σ-bond. The FCCH, ClCCH, BrCCH and ICCH species, as well as the F2, Cl2, Br2 and I2 molecular halogens, act as Lewis acid units in these complexes, interacting through the σ-hole localised at the halogen centre. The Quantum Theory of Atoms in Molecules (QTAIM), the Natural Bond Orbital (NBO) and the Energy Decomposition Analysis (EDA) approaches were applied to analyse these aforementioned complexes. These complexes may be classified as linked by A–X···σ halogen bonds, where A = C, X (halogen). However, distinct properties of these halogen bonds are observed that depend partly on the kind of electron donor: dihydrogen, cyclopropane, or another cycloalkane. Examples of similar interactions that occur in crystals are presented; Cambridge Structural Database (CSD) searches were carried out to find species linked by the A–X···σ halogen bonds.

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20

Sirirak, Jitnapa, Wasinee Phonsri, David J. Harding, Phimphaka Harding, Pimonrat Phommon, Wannapa Chaoprasa, Rebecca M. Hendry, Thomas M. Roseveare, and Harry Adams. "Halogen substituted quinolylsalicylaldimines: Four halogens three structural types." Journal of Molecular Structure 1036 (March 2013): 439–46. http://dx.doi.org/10.1016/j.molstruc.2012.11.028.

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21

Adonin, Sergey A., Mikhail A. Bondarenko, Alexander S. Novikov, and Maxim N. Sokolov. "Halogen Bonding in Isostructural Co(II) Complexes with 2-Halopyridines." Crystals 10, no. 4 (April 10, 2020): 289. http://dx.doi.org/10.3390/cryst10040289.

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Three complexes [Co(2-XPy)2Cl2] (X = Cl, Br, and I) were prepared and characterized, representing a rare case of isostructurality within the Cl-Br-I row. The nature of halogen bonding (XB) in a solid state was studied by DFT calculations, revealing a tendency of XB energy growth for heavier halogens.

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Navon, Oshrit, Joel Bernstein, and Vladimir Khodorkovsky. "Chains, Ladders, and Two-Dimensional Sheets with Halogenċ Halogen and Halogenċ Hydrogen Interactions." Angewandte Chemie International Edition in English 36, no. 6 (April 4, 1997): 601–3. http://dx.doi.org/10.1002/anie.199706011.

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23

Neopane, S., and N. Pantha. "First-Principles Study of Van Der Waals Interactions between Halogen Molecules (Cl2 and I2)." Journal of Nepal Physical Society 5, no. 1 (December 26, 2019): 19–23. http://dx.doi.org/10.3126/jnphyssoc.v5i1.26878.

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Density Functional Theory (DFT) based first-principles calculations have been performed to investigate vander Waals (vdW) interactions in between halogen atoms/molecules —Cl-Cl, I-I, Cl2-Cl2, Cl2-I2, I2-I2—via with and without a non-local exchange-correlation (XC) functional (vdW-DF) using Quantum ESPRESSO codes. The non-polar covalent bond length between atomic halogens (Cl-Cl and I-I) is not observed to be affected by vdW interactions and agrees well with experimental values. The binding energy between theatomic halogens, on the other hand, is slightly corrected by vdW interactions. However, the role of vdW interactions is observed to be crucial to bind molecular halogens. The molecules are weakly bound in the presence of vdW interactions and not correlated (bound) in the absence of them.

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Rossi, Laura I., and Manuel I. Velasco. "Alternatives to free molecular halogens as chemoselective reactants: Catalysis of organic reactions with reusable complexes of halogen metal salts." Pure and Applied Chemistry 84, no. 3 (February 6, 2012): 819–26. http://dx.doi.org/10.1351/pac-con-11-07-13.

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Organometallic complexes of halogen metallic salts have been used as catalysts in different organic reactions, mainly the oxidation of organic compounds. Their use has not only allowed the reduction of the amounts of catalyst (since they can be reused) but also a lower generation of byproducts and wastes. The different reaction media developed through the research were analyzed by several green parameters, and the best results were obtained with complexes that have cyclodextrins as organic ligands. The proposed methodology is an alternative to use of molecular halogen as oxidant or catalyst when halogens are significant chemoselective reactants.

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Simpson, W. R., D. Carlson, G. Hönninger, T. A. Douglas, M. Sturm, D. Perovich, and U. Platt. "First-year sea-ice contact predicts bromine monoxide (BrO) levels at Barrow, Alaska better than potential frost flower contact." Atmospheric Chemistry and Physics 7, no. 3 (February 9, 2007): 621–27. http://dx.doi.org/10.5194/acp-7-621-2007.

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Abstract. Reactive halogens are responsible for boundary-layer ozone depletion and mercury deposition in Polar Regions during springtime. To investigate the source of reactive halogens in the air arriving at Barrow, Alaska, we measured BrO, an indicator of reactive halogen chemistry, and correlated its abundance with airmass histories derived from meteorological back trajectories and remotely sensed sea ice properties. The BrO abundance is found to be positively correlated to first-year sea-ice contact (R2=0.55), and essentially uncorrelated with potential frost flower (PFF) contact (R2=0.04). Assuming that PFF accurately predicts frost flowers, these data indicate that snow and ice contaminated with sea salts on first-year sea ice is a more probable bromine source than are frost flowers, for airmasses impacting Barrow, Alaska. Climate-driven changes in Arctic sea ice are likely to alter frost flower and first year sea ice prevalence. An accurate understanding of how these sea ice changes would affect the halogen chemistry of the overlying atmosphere depends upon understanding the relative roles of frost flowers and saline snow and ice surfaces as reactive bromine sources.

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Pourmoghaddas, H., and A. A. Stevens. "Relationship between trihalomethanes and haloacetic acids with total organic halogen during chlorination." Water Supply 2, no. 5-6 (December 1, 2002): 509–14. http://dx.doi.org/10.2166/ws.2002.0211.

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The effects of bromide ion, pH and reaction time on the formation of four trihalomethanes, nine haloacetic acids and total organic halogens in chlorinated drinking water have been investigated. In this extensive study, the relationship of total trihalomethanes and total haloacetic acids with total organic halogen have been evaluated. The study determined the concentration range of nine haloacetic acids and four trihalomethanes as a percentage of total organic halogen. The results showed that the percentage of total organic halogen made up of total trihalomethanes plus total haloacetic acids significantly increases with increasing bromide ion concentrations and pH. These observations suggest that both a higher bromide concentration and pH cause the formation of mainly brominated trihalomethanes with the reduction of haloacetic acids which could be identified and quantified by current USEPA methods.

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27

China, Hideyasu, Ravi Kumar, Kotaro Kikushima, and Toshifumi Dohi. "Halogen-Induced Controllable Cyclizations as Diverse Heterocycle Synthetic Strategy." Molecules 25, no. 24 (December 18, 2020): 6007. http://dx.doi.org/10.3390/molecules25246007.

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In organic synthesis, due to their high electrophilicity and leaving group properties, halogens play pivotal roles in the activation and structural derivations of organic compounds. Recently, cyclizations induced by halogen groups that allow the production of diverse targets and the structural reorganization of organic molecules have attracted significant attention from synthetic chemists. Electrophilic halogen atoms activate unsaturated and saturated hydrocarbon moieties by generating halonium intermediates, followed by the attack of carbon-containing, nitrogen-containing, oxygen-containing, and sulfur-containing nucleophiles to give highly functionalized carbocycles and heterocycles. New transformations of halogenated organic molecules that can control the formation and stereoselectivity of the products, according to the difference in the size and number of halogen atoms, have recently been discovered. These unique cyclizations may possibly be used as efficient synthetic strategies with future advances. In this review, innovative reactions controlled by halogen groups are discussed as a new concept in the field of organic synthesis.

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28

Galeotti, Gianluca, Marco Di Giovannantonio, Josh Lipton-Duffin, Maryam Ebrahimi, Stefano Tebi, Alberto Verdini, Luca Floreano, et al. "The role of halogens in on-surface Ullmann polymerization." Faraday Discussions 204 (2017): 453–69. http://dx.doi.org/10.1039/c7fd00099e.

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Ullmann coupling is the most common approach to form surface-confined one- and two-dimensional conjugated structures from haloaryl derivatives. The dimensions of the formed nanostructures can be controlled by the number and location of halogens within the molecular precursors. Our study illustrates that the type of halogen plays an essential role in the design, orientation, and extent of the surface-confined organometallic and polymeric nanostructures. We performed a comparative analysis of five 1,4-dihalobenzene molecules containing chlorine, bromine, and iodine on Cu(110) using scanning tunneling microscopy, fast-X-ray photoelectron and near edge X-ray absorption fine structure spectroscopies. Our experimental data identify different molecular structures, reaction temperatures and kinetics depending on the halogen type. Climbing image nudged elastic band simulations further clarify these observations by providing distinct diffusion paths for each halogen species. We show that in addition to the structure of the building blocks, the halogen type has a direct influence on the morphology of surface-confined polymeric structures based on Ullmann coupling.

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Fang, Hong, and Puru Jena. "Super-ion inspired colorful hybrid perovskite solar cells." Journal of Materials Chemistry A 4, no. 13 (2016): 4728–37. http://dx.doi.org/10.1039/c5ta09646d.

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Hybrid perovskites viewed as super alkali halides with alkali and halogen ions replaced by super alkalis and super halogens, respectively. The basic properties of these materials are determined by the bonding ionicity and effective ionic radii of the super-ions. New colorful hybrid perovskites can be invented with super-ions as the building block.

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30

Sherwen, T., M. J. Evans, R. Sommariva, L. D. J. Hollis, S. M. Ball, P. S. Monks, C. Reed, et al. "Effects of halogens on European air-quality." Faraday Discussions 200 (2017): 75–100. http://dx.doi.org/10.1039/c7fd00026j.

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Halogens (Cl, Br) have a profound influence on stratospheric ozone (O₃). They (Cl, Br and I) have recently also been shown to impact the troposphere, notably by reducing the mixing ratios of O₃ and OH. Their potential for impacting regional air-quality is less well understood. We explore the impact of halogens on regional pollutants (focussing on O₃) with the European grid of the GEOS-Chem model (0.25° × 0.3125°). It has recently been updated to include a representation of halogen chemistry. We focus on the summer of 2015 during the ICOZA campaign at the Weybourne Atmospheric Observatory on the North Sea coast of the UK. Comparisons between these observations together with those from the UK air-quality network show that the model has some skill in representing the mixing ratios/concentration of pollutants during this period. Although the model has some success in simulating the Weybourne ClNO₂ observations, it significantly underestimates ClNO₂ observations reported at inland locations. It also underestimates mixing ratios of IO, OIO, I₂ and BrO, but this may reflect the coastal nature of these observations. Model simulations, with and without halogens, highlight the processes by which halogens can impact O₃. Throughout the domain O₃ mixing ratios are reduced by halogens. In northern Europe this is due to a change in the background O₃ advected into the region, whereas in southern Europe this is due to local chemistry driven by Mediterranean emissions. The proportion of hourly O₃ above 50 nmol mol⁻¹ in Europe is reduced from 46% to 18% by halogens. ClNO₂ from N₂O₅ uptake onto sea-salt leads to increases in O₃ mixing ratio, but these are smaller than the decreases caused by the bromine and iodine. 12% of ethane and 16% of acetone within the boundary layer is oxidised by Cl. Aerosol response to halogens is complex with small (∼10%) reductions in PM_2.5 in most locations. A lack of observational constraints coupled to large uncertainties in emissions and chemical processing of halogens make these conclusions tentative at best. However, the results here point to the potential for halogen chemistry to influence air quality policy in Europe and other parts of the world.

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Thornton, Nicholas J., and Tanja van Mourik. "Halogen-Bonded Guanine Base Pairs, Quartets and Ribbons." International Journal of Molecular Sciences 21, no. 18 (September 8, 2020): 6571. http://dx.doi.org/10.3390/ijms21186571.

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Halogen bonding is studied in different structures consisting of halogenated guanine DNA bases, including the Hoogsteen guanine–guanine base pair, two different types of guanine ribbons (R-I and R-II) consisting of two or three monomers, and guanine quartets. In the halogenated base pairs (except the Cl-base pair, which has a very non-planar structure with no halogen bonds) and R-I ribbons (except the At trimer), the potential N-X•••O interaction is sacrificed to optimise the N-X•••N halogen bond. In the At trimer, the astatines originally bonded to N1 in the halogen bond donating guanines have moved to the adjacent O6 atom, enabling O-At•••N, N-At•••O, and N-At•••At halogen bonds. The brominated and chlorinated R-II trimers contain two N-X•••N and two N-X•••O halogen bonds, whereas in the iodinated and astatinated trimers, one of the N-X•••N halogen bonds is lost. The corresponding R-II dimers keep the same halogen bond patterns. The G-quartets display a rich diversity of symmetries and halogen bond patterns, including N-X•••N, N-X•••O, N-X•••X, O-X•••X, and O-X•••O halogen bonds (the latter two facilitated by the transfer of halogens from N1 to O6). In general, halogenation decreases the stability of the structures. However, the stability increases with the increasing atomic number of the halogen, and the At-doped R-I trimer and the three most stable At-doped quartets are more stable than their hydrogenated counterparts. Significant deviations from linearity are found for some of the halogen bonds (with halogen bond angles around 150°).

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32

Lehrer, E., G. Hönninger, and U. Platt. "A one dimensional model study of the mechanism of halogen liberation and vertical transport in the polar troposphere." Atmospheric Chemistry and Physics 4, no. 11/12 (December 6, 2004): 2427–40. http://dx.doi.org/10.5194/acp-4-2427-2004.

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Abstract. Sudden depletions of tropospheric ozone during spring were reported from the Arctic and also from Antarctic coastal sites. Field studies showed that those depletion events are caused by reactive halogen species, especially bromine compounds. However the source and seasonal variation of reactive halogen species is still not completely understood. There are several indications that the halogen mobilisation from the sea ice surface of the polar oceans may be the most important source for the necessary halogens. Here we present a one dimensional model study aimed at determining the primary source of reactive halogens. The model includes gas phase and heterogeneous bromine and chlorine chemistry as well as vertical transport between the surface and the top of the boundary layer. The autocatalytic Br release by photochemical processes (bromine explosion) and subsequent rapid bromine catalysed ozone depletion is well reproduced in the model and the major source of reactive bromine appears to be the sea ice surface. The sea salt aerosol alone is not sufficient to yield the high levels of reactive bromine in the gas phase necessary for fast ozone depletion. However, the aerosol efficiently "recycles" less reactive bromine species (e.g. HBr) and feeds them back into the ozone destruction cycle. Isolation of the boundary layer air from the free troposphere by a strong temperature inversion was found to be critical for boundary layer ozone depletion to happen. The combination of strong surface inversions and presence of sunlight occurs only during polar spring.

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33

Lehrer, E., G. Hönninger, and U. Platt. "The mechanism of halogen liberation in the polar troposphere." Atmospheric Chemistry and Physics Discussions 4, no. 3 (June 28, 2004): 3607–52. http://dx.doi.org/10.5194/acpd-4-3607-2004.

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Abstract. Sudden depletions of tropospheric ozone during spring were reported from the Arctic and also from Antarctic coastal sites. Field studies showed that those depletion events are caused by reactive halogen species, especially bromine compounds. However the source and seasonal variation of reactive halogen species is still not completely understood. There are several indications that the halogen mobilisation from the sea ice surface of the polar oceans may be the most important source for the necessary halogens. Here we present a 1-D model study aimed at determining the primary source of reactive halogens. The model includes gas phase and heterogeneous bromine and chlorine chemistry as well as vertical transport between the surface and the top of the boundary layer. The autocatalytic Br release by photochemical processes (bromine explosion) and subsequent rapid bromine catalysed ozone depletion is well reproduced in the model and the major source of reactive bromine appears to be the sea ice surface. The sea salt aerosol alone is not sufficient to yield the high levels of reactive bromine in the gas phase necessary for fast ozone depletion. However, the aerosol efficiently 'recycles' less reactive bromine species (e.g. HBr) and feeds them back into the ozone destruction cycle. Isolation of the boundary layer air from the free troposphere by a strong temperature inversion was found to be critical for boundary layer ozone depletion to happen. The combination of strong surface inversions and presence of sunlight occurs only during polar spring.

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34

Long, M. S., W. C. Keene, R. C. Easter, R. Sander, X. Liu, A. Kerkweg, and D. Erickson. "Sensitivity of tropospheric chemical composition to halogen-radical chemistry using a fully coupled size-resolved multiphase chemistry/global climate system – Part 1: Halogen distributions, aerosol composition, and sensitivity of climate-relevant gases." Atmospheric Chemistry and Physics Discussions 13, no. 3 (March 7, 2013): 6067–129. http://dx.doi.org/10.5194/acpd-13-6067-2013.

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Abstract. Observations and model studies suggest a significant but highly non-linear role for halogens, primarily Cl and Br, in multiphase atmospheric processes relevant to tropospheric chemistry and composition, aerosol evolution, radiative transfer, weather, and climate. The sensitivity of global atmospheric chemistry to the production of marine aerosol and the associated activation and cycling of inorganic Cl and Br was tested using a size-resolved multiphase coupled chemistry/global climate model (National Center for Atmospheric Research's Community Atmosphere Model (CAM); v3.6.33). Simulation results showed strong meridional and vertical gradients in Cl and Br species. The simulation reproduced most available observations with reasonable confidence permitting the formulation of potential mechanisms for several previously unexplained halogen phenomena including the enrichment of Br− in submicron aerosol, and the presence of a BrO maximum in the polar free troposphere. However, simulated total volatile Br mixing ratios were generally high in the troposphere. Br in the stratosphere was lower than observed due to the lack of long-lived organobromine species in the simulation. Comparing simulations using chemical mechanisms with and without reactive Cl and Br species demonstrated a significant temporal and spatial sensitivity of primary atmospheric oxidants (O3, HOx, NOx), CH4, and non-methane hydrocarbons (NMHC's) to halogen cycling. Simulated O3 and NOx were globally lower (65% and 35%, respectively, less in the planetary boundary layer based on median values) in simulations that included halogens. Globally, little impact was seen in SO2 and non-sea-salt SO42− processing due to halogens. Significant regional differences were evident: the lifetime of nss-SO42− was extended downwind of large sources of SO2. The burden and lifetime of DMS (and its oxidation products) were lower by a factor of 5 in simulations that included halogens, versus those without, leading to a 20% reduction in nss-SO42− in the Southern Hemisphere planetary boundary layer based on median values.

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35

Mathew, Bijo, Simone Carradori, Paolo Guglielmi, Md Sahab Uddin, and Hoon Kim. "New Aspects of Monoamine Oxidase B Inhibitors: The Key Role of Halogens to Open the Golden Door." Current Medicinal Chemistry 28, no. 2 (December 30, 2020): 266–83. http://dx.doi.org/10.2174/0929867327666200121165931.

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A large plethora of drugs and promising lead compounds contain halogens in their structures. The introduction of such moieties strongly modulates their physical-chemical features as well as pharmacokinetic and pharmacodynamic profile. The most important outcome was shown to be the ability of these halogens to favourably influence the drug-target interaction and energetic stability within the active site by the establishment of halogen bonds. This review attempted to demonstrate the key role exerted by these versatile moieties when correctly located in an organic scaffold to display Monoamine Oxidase (MAO) inhibition and selectivity towards the B isoform of this important enzyme. Human MAOs are well-recognized as therapeutic targets for mood disorders and neurodegenerative diseases and medicinal chemists were prompted to discover the structural requirements crucial to discriminate the slight differences between the active sits of the two isoforms (MAO-A and MAOB). The analysis of the structure-activity relationships of the most important scaffolds (hydrazothiazoles, coumarins, chromones, chalcones, pyrazolines) and the impact of halogen (F, Cl, Br and I) insertion on this biological activity and isozyme selectivity have been reported being a source of inspiration for the medicinal chemists.

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36

Wang, Ruimin, Janine George, Shannon Kimberly Potts, Marius Kremer, Richard Dronskowski, and Ulli Englert. "The many flavours of halogen bonds – message from experimental electron density and Raman spectroscopy." Acta Crystallographica Section C Structural Chemistry 75, no. 9 (August 22, 2019): 1190–201. http://dx.doi.org/10.1107/s205322961901132x.

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Experimental electron-density studies based on high-resolution diffraction experiments allow halogen bonds between heavy halogens to be classified. The topological properties of the electron density in Cl...Cl contacts vary smoothly as a function of the interaction distance. The situation is less straightforward for halogen bonds between iodine and small electronegative nucleophiles, such as nitrogen or oxygen, where the electron density in the bond critical point does not simply increase for shorter distances. The number of successful charge–density studies involving iodine is small, but at least individual examples for three cases have been observed. (a) Very short halogen bonds between electron-rich nucleophiles and heavy halogen atoms resemble three-centre–four-electron bonds, with a rather symmetric heavy halogen and without an appreciable σ hole. (b) For a narrow intermediate range of halogen bonds, the asymmetric electronic situation for the heavy halogen with a pronounced σ hole leads to rather low electron density in the (3,−1) critical point of the halogen bond; the properties of this bond critical point cannot fully describe the nature of the associated interaction. (c) For longer and presumably weaker contacts, the electron density in the halogen bond critical point is only to a minor extent reduced by the presence of the σ hole and hence may be higher than in the aforementioned case. In addition to the electron density and its derived properties, the halogen–carbon bond distance opposite to the σ hole and the Raman frequency for the associated vibration emerge as alternative criteria to gauge the halogen-bond strength. We find exceptionally long C—I distances for tetrafluorodiiodobenzene molecules in cocrystals with short halogen bonds and a significant red shift for their Raman vibrations.

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37

Ostras’, Alexei S., Daniil M. Ivanov, Alexander S. Novikov, and Peter M. Tolstoy. "Phosphine Oxides as Spectroscopic Halogen Bond Descriptors: IR and NMR Correlations with Interatomic Distances and Complexation Energy." Molecules 25, no. 6 (March 19, 2020): 1406. http://dx.doi.org/10.3390/molecules25061406.

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An extensive series of 128 halogen-bonded complexes formed by trimethylphosphine oxide and various F-, Cl-, Br-, I- and At-containing molecules, ranging in energy from 0 to 124 kJ/mol, is studied by DFT calculations in vacuum. The results reveal correlations between R–X⋅⋅⋅O=PMe3 halogen bond energy ΔE, X⋅⋅⋅O distance r, halogen’s σ-hole size, QTAIM parameters at halogen bond critical point and changes of spectroscopic parameters of phosphine oxide upon complexation, such as 31P NMR chemical shift, ΔδP, and P=O stretching frequency, Δν. Some of the correlations are halogen-specific, i.e., different for F, Cl, Br, I and At, such as ΔE(r), while others are general, i.e., fulfilled for the whole set of complexes at once, such as ΔE(ΔδP). The proposed correlations could be used to estimate the halogen bond properties in disordered media (liquids, solutions, polymers, glasses) from the corresponding NMR and IR spectra.

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38

Frenzel, Max, Nigel J. Cook, Cristiana L. Ciobanu, Ashley D. Slattery, Benjamin P. Wade, Sarah Gilbert, Kathy Ehrig, Mathias Burisch, Max R. Verdugo-Ihl, and Panagiotis Voudouris. "Halogens in hydrothermal sphalerite record origin of ore-forming fluids." Geology 48, no. 8 (May 12, 2020): 766–70. http://dx.doi.org/10.1130/g47087.1.

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Abstract The halogens Cl and Br are sensitive indicators for the origin of ore-forming fluids. Here, we use a combination of microchemical and microscopic methods to show that measurable concentrations of these elements commonly occur as atomic-scale substitutions in hydrothermal sphalerite. Furthermore, the Cl/Br ratios of halogen-rich sphalerites are indistinguishable from those of the corresponding ore-forming fluids. Thus, they record fluid compositions, which in turn record fluid origin. Given the abundance of sphalerite in hydrothermal base-metal deposits, as well as the relative ease of conducting in situ microchemical analyses, the halogen signature of sphalerite has the potential to become a sensitive proxy to distinguish between different ore-forming environments.

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39

Kumar, Rakesh, Frank Ke, Dustin England, Angie Summers, and Lamar Young. "A New Halogen-Free Parylene for High Performance & Reliability of Microelectronics in Harsh Environments." International Symposium on Microelectronics 2019, no. 1 (October 1, 2019): 000085–90. http://dx.doi.org/10.4071/2380-4505-2019.1.000085.

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Abstract The rapid growth and adoption of microelectronics around the world has resulted in an increased awareness of potential environmental issues related to their use and disposal. Halogens, which have had various uses in microelectronics over the years, are known to emit toxic and corrosive gases during the disposal of electronic waste. Many organizations have applied pressure to the electronics industry to eliminate halogens completely (e.g., fluorine, chlorine and bromine) from their products. Among the various efforts towards environmentally-friendly products, making electronics completely halogen-free has gained significant attention, particularly in Asia and Europe. This initiative even impacts conformal coatings worldwide, on which most electronics rely for their long-term protection, reliability and high performance against water and other corrosive harsh environments. Among the various coating options, the Parylene family of conformal coatings offers beneficial properties to the microelectronics, improved over many properties offered by common epoxies, acrylics, urethanes and silicones. While Parylene N is the only commercially available Parylene that does not contain any halogens, its barrier performance against moisture and other corrosive chemicals is not quite as robust as the other Parylenes. To meet the industry's current and future requirements, a new halogen-free Parylene, ParyFree®, has been developed. This paper introduces a new Parylene type to the microelectronics industry and shares the characterization and qualification results of ParyFree® Parylene conformal coating for the protection, reliability and robust performance of microelectronics. Testing on the new coating includes IPX water resistance, corrosion resistance and qualification per IPC-CC-830B.

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40

Kumar, Rakesh, Frank Ke, Dustin England, Angie Summers, and Lamar Young. "A New Halogen-Free Parylene for High Performance and Reliability of Microelectronics in Harsh Environments." Journal of Microelectronics and Electronic Packaging 17, no. 3 (July 1, 2020): 73–78. http://dx.doi.org/10.4071/imaps.1120416.

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Abstract The rapid growth and adoption of microelectronics around the world has resulted in an increased awareness of potential environmental issues related to their use and disposal. Halogens, which have had various uses in microelectronics over the years, are known to emit toxic and corrosive gases during the disposal of electronic waste. Many organizations have applied pressure to the electronics industry to eliminate halogens completely (e.g., fluorine, chlorine, and bromine) from their products. Among the various efforts toward environmentally friendly products, making electronics completely halogen-free has gained significant attention, particularly in Asia and Europe. This initiative even impacts conformal coatings worldwide, on which most electronics rely for their long-term protection, reliability, and high performance against water and other corrosive harsh environments. Among the various coating options, the parylene family of conformal coatings offers beneficial properties to the microelectronics, improved over many properties offered by common epoxies, acrylics, urethanes, and silicones. Although parylene N is the only commercially available parylene that does not contain any halogens, its barrier performance against moisture and other corrosive chemicals is not quite as robust as the other parylenes. To meet the industry’s current and future requirements, a new halogen-free parylene, ParyFree®, has been developed. This study introduces a new parylene type to the microelectronics industry and shares the characterization and qualification results of ParyFree® parylene conformal coating for the protection, reliability, and robust performance of microelectronics. Testing on the new coating includes IPX water resistance, corrosion resistance, and qualification per IPC-CC-830B.

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Boule, P., K. Othmen, C. Richard, B. Szczepanik, and G. Grabner. "Phototransformation of halogenoaromatic derivatives in aqueous solution." International Journal of Photoenergy 1, no. 1 (1999): 49–54. http://dx.doi.org/10.1155/s1110662x99000094.

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The photochemical behaviour of monohalogeno-phenols and -anilines is highly dependent on the position of the halogen on the ring, but most often it is not significantly influenced by the nature of the halogen (Cl, Br, F). Photohydrolysis is the main reaction observed with 3-halogenated and it is almost specific. With 2-halogenated, photohydrolysis and photocontraction of the ring compete, the latter being very efficient with 2-halogeno-phenolates.The photochemical behaviour of 4-halogeno-phenols and -anilines is more complex. It depends on both concentration and oxygenation. It was rationalized when it was experimentally proved by laser flash photolysis that the first step is the formation of a carbene (in the cationic form in the case of 4-halogenoaniline).ρ-Benzoquinone is the product of photooxidation of 4-halogenophenols, whereas the photooxidation of 4-chloroaniline leads to 4-amino-4´-chlorodiphenylamine.Chlorohydroquinone behaves differently, the formation of the main photoproducts involving a radical mechanism.With dihalogenoanilines photohydrolysis is initially almost quantitative whatever the position of halogen atom on the ring. It occurs more easily in meta than inorthoposition and inorthothan inparaposition. In the case of 2,4- and 2,6-dichloroanilines aminophenoxazones are formed as secondary photoproducts. This reaction involves the intermediate formation of o-benzoquinone monoimine. Several halogenoaromatic herbicides were also studied (bromoxynil, chlorpropham, propanil, diuron, linuron, chlorbromuron, MCPA). The most frequent reaction is photohydrolysis. However some other reactions such as photoreduction and photo-demethoxylation were observed. In some cases a wavelength effect was observed particularly with MCPA and halogenophenylureas.

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Kaźmierczak, Michał, and Andrzej Katrusiak. "The shortest chalcogen...halogen contacts in molecular crystals." Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 75, no. 5 (September 19, 2019): 865–69. http://dx.doi.org/10.1107/s2052520619011004.

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The survey of the shortest contacts in structures deposited in the Cambridge Structural Database shows that chalcogen...halogen, halogen...halogen and chalcogen...chalcogen interactions can compete as cohesion forces in molecular crystals. The smallest parameter δ (defined as the interatomic distance minus the sum of relevant van der Waals radii) for Ch...X contacts between chalcogens (Ch: S, Se) and halogens (X: F, Cl, Br, I) is present only in 0.86% out of 30 766 deposited structures containing these atoms. Thus, in less than 1% of these structures can the Ch...X forces be considered as the main type of cohesion forces responsible for the molecular arrangement. Among the 263 structures with the shortest Ch...X contact, there are four crystals where no contacts shorter than the sums of van der Waals radii are present (so-called loose crystals). The smallest δ criterion has been used for distinguishing between the bonding (covalent bond) and non-bonding contacts and for validating the structural models of crystals.

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43

Li, Qinyi, Rafael Borge, Golam Sarwar, David de la Paz, Brett Gantt, Jessica Domingo, Carlos A. Cuevas, and Alfonso Saiz-Lopez. "Impact of halogen chemistry on summertime air quality in coastal and continental Europe: application of the CMAQ model and implications for regulation." Atmospheric Chemistry and Physics 19, no. 24 (December 16, 2019): 15321–37. http://dx.doi.org/10.5194/acp-19-15321-2019.

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Abstract. Halogen (Cl, Br, and I) chemistry has been reported to influence the formation of secondary air pollutants. Previous studies mostly focused on the impact of chlorine species on air quality over large spatial scales. Very little attention has been paid to the effect of the combined halogen chemistry on air quality over Europe and its implications for control policy. In the present study, we apply a widely used regional model, the Community Multiscale Air Quality Modeling System (CMAQ), incorporated with the latest halogen sources and chemistry, to simulate the abundance of halogen species over Europe and to examine the role of halogens in the formation of secondary air pollution. The results suggest that the CMAQ model is able to reproduce the level of O3, NO2, and halogen species over Europe. Chlorine chemistry slightly increases the levels of OH, HO2, NO3, O3, and NO2 and substantially enhances the level of the Cl radical. Combined halogen chemistry induces complex effects on OH (ranging from −0.023 to 0.030 pptv) and HO2 (in the range of −3.7 to 0.73 pptv), significantly reduces the concentrations of NO3 (as much as 20 pptv) and O3 (as much as 10 ppbv), and decreases NO2 in highly polluted regions (as much as 1.7 ppbv); it increases NO2 (up to 0.20 ppbv) in other areas. The maximum effects of halogen chemistry occur over oceanic and coastal regions, but some noticeable impacts also occur over continental Europe. Halogen chemistry affects the number of days exceeding the European Union target threshold for the protection of human beings and vegetation from ambient O3. In light of the significant impact of halogen chemistry on air quality, we recommend that halogen chemistry be considered for inclusion in air quality policy assessments, particularly in coastal cities.

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44

Wu, Qiong, Jian-Chang Xiao, Cun Zhou, Jin-Rong Sun, Mei-Fen Huang, Xindi Xu, Tianyu Li, and Hui Tian. "Crystal Structure and Supramolecular Architecture of Inorganic Ligand-Coordinated Salen-Type Schiff Base Complex: Insights into Halogen Bond from Theoretical Analysis and 3D Energy Framework Calculations." Crystals 10, no. 4 (April 23, 2020): 334. http://dx.doi.org/10.3390/cryst10040334.

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To identify the effects of halogen bonding in the architecture of Schiff base complex supramolecular networks, we introduced halogenated Schiff-base 3-Br-5-Cl-salen as ligand and isolated a new salen-type manganese(III) complex [MnIII(Cl)(H2O)(3-Br-5-Cl-salen)] (1) where 3-Br-5-Cl-salen = N,N’-bis(3-bromo-5-chlorosalicylidene)-1,2-diamine. The complex was investigated in the solid-state for halogen bonds (XBs) by single crystal X-ray structure analysis. Meanwhile, theoretical calculations were carried out to rationalize the formation mechanism of different types of XBs in the complex. The analysis result of electronic structure of the halogen bonds indicated that the chlorine atom coordinated to the Mn(III) center possesses the most negative potential and acts as anionic XB acceptor (electron donor) to the adjacent substituted halogens on the ligand, meanwhile the intermolecular Mn-Cl···X-C halogen bonding plays a significant role in directing the packing arrangement of adjacent molecules and linking the 2D layers into a 3D network. In order to verify the above results and acquire detailed information, the title complex was further analyzed by using the Hirshfeld surface analyses.

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45

El-Said, Ghada F., Gehan M. El Zokm, Abeer A. El Sayed, Ahmed A. El Ashmawy, and Mohamed A. Shreadah. "Anomalous Fluctuation of Halogens in Relation to the Pollution Status along Lake Mariout, Egypt." Journal of Chemistry 2020 (December 30, 2020): 1–20. http://dx.doi.org/10.1155/2020/8102081.

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This paper aimed to study the anomalous fluctuation of halogens with respect to the pollution status in surface water (w), pore water (p), and sediments (s) of Lake Mariout. It provided a framework for understanding the distribution of dissolved and precipitated halogen salts related to the pollution status of the lake. The study cleared out that bromide was only the most abundant halogen in the three studied partitions. On contrast, sediment’s partition contained the lowest chloride content. Fluoride minerals, especially, fluorapatites and carbonate-fluorapatite (FAP and CFAP), had high Saturation Index (SI) values in surface water (42.77–51.95 and 16.04–60.89, respectively) and in pore water (51.26–54.60 and 17.52–78.33, respectively). Bromide and chloride were mainly found in the soluble forms in the surface water and pore waters. Iodide salts, (Ca(IO3)2 and Ca(IO3)2.6H2O), were moderately precipitated in surface and pore waters. Thus, SI content reflected that halogens, especially fluoride and iodide, played a vital role in reducing lake pollution. Fluorite (CaF2) and sellaïte (MgF2) could only be formed in pore water, while calcite and aragonite could be deposited from surface water. In addition, Cl was mainly found in the forms of NaCl, CaCl2, MgCl2, and KCl in surface and pore waters. The multivariate analysis revealed that fluoride precipitate may serve in decreasing the dissolved salt pollution. Multivariate analysis showed that in the long run, the fluoride precipitation in FAP and CFAP can significantly adsorb and absorb various pollutants and can protect the lake from pollution. The ecological risk assessment conducted by calculating the enrichment factor (EF) showed that the lake was still unpolluted. Regarding human health risks, at appropriate levels of human health and safety, the hazard quotient (HQ) and hazard index (HI) of halogens found to be lower than these reported levels. Hence, ingestion and dermal absorption routes of halogens by surface water and sediments did not pose any adverse effects to population reflecting uncontaminated status of Lake Mariout.

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Sherwen, Tomás, Johan A. Schmidt, Mat J. Evans, Lucy J. Carpenter, Katja Großmann, Sebastian D. Eastham, Daniel J. Jacob, et al. "Global impacts of tropospheric halogens (Cl, Br, I) on oxidants and composition in GEOS-Chem." Atmospheric Chemistry and Physics 16, no. 18 (September 29, 2016): 12239–71. http://dx.doi.org/10.5194/acp-16-12239-2016.

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Abstract. We present a simulation of the global present-day composition of the troposphere which includes the chemistry of halogens (Cl, Br, I). Building on previous work within the GEOS-Chem model we include emissions of inorganic iodine from the oceans, anthropogenic and biogenic sources of halogenated gases, gas phase chemistry, and a parameterised approach to heterogeneous halogen chemistry. Consistent with Schmidt et al. (2016) we do not include sea-salt debromination. Observations of halogen radicals (BrO, IO) are sparse but the model has some skill in reproducing these. Modelled IO shows both high and low biases when compared to different datasets, but BrO concentrations appear to be modelled low. Comparisons to the very sparse observations dataset of reactive Cl species suggest the model represents a lower limit of the impacts of these species, likely due to underestimates in emissions and therefore burdens. Inclusion of Cl, Br, and I results in a general improvement in simulation of ozone (O3) concentrations, except in polar regions where the model now underestimates O3 concentrations. Halogen chemistry reduces the global tropospheric O3 burden by 18.6 %, with the O3 lifetime reducing from 26 to 22 days. Global mean OH concentrations of 1.28 × 106 molecules cm−3 are 8.2 % lower than in a simulation without halogens, leading to an increase in the CH4 lifetime (10.8 %) due to OH oxidation from 7.47 to 8.28 years. Oxidation of CH4 by Cl is small (∼ 2 %) but Cl oxidation of other VOCs (ethane, acetone, and propane) can be significant (∼ 15–27 %). Oxidation of VOCs by Br is smaller, representing 3.9 % of the loss of acetaldehyde and 0.9 % of the loss of formaldehyde.

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47

Havránek, Miroslav, Maksim A. Samsonov, Josef Holub, Zdeňka Růžičková, Ladislav Drož, Aleš Růžička, Jindřich Fanfrlík, and Drahomír Hnyk. "The Influence of Halogenated Hypercarbon on Crystal Packing in the Series of 1-Ph-2-X-1,2-dicarba-closo-dodecaboranes (X = F, Cl, Br, I)." Molecules 25, no. 5 (March 6, 2020): 1200. http://dx.doi.org/10.3390/molecules25051200.

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Although 1-Ph-2-X-closo-1,2-C2B10H10 (X = F, Cl, Br, I) derivatives had been computed to have positive values of the heat of formation, it was possible to prepare them. The corresponding solid-state structures were computationally analyzed. Electrostatic potential computations indicated the presence of highly positive σ-holes in the case of heavy halogens. Surprisingly, the halogen•••π interaction formed by the Br atom was found to be more favorable than that of I.

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48

Nikitin, Igor V. "Oxygen compounds of halogens X2O2(X is a halogen atom)." Russian Chemical Reviews 71, no. 2 (February 28, 2002): 85–97. http://dx.doi.org/10.1070/rc2002v071n02abeh000684.

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49

Spolaor, A., P. Vallelonga, J. Gabrieli, T. Martma, M. P. Björkman, E. Isaksson, G. Cozzi, et al. "Seasonality of halogen deposition in polar snow and ice." Atmospheric Chemistry and Physics 14, no. 18 (September 16, 2014): 9613–22. http://dx.doi.org/10.5194/acp-14-9613-2014.

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Abstract. The atmospheric chemistry of iodine and bromine in Polar regions is of interest due to the key role of halogens in many atmospheric processes, particularly tropospheric ozone destruction. Bromine is emitted from the open ocean but is enriched above first-year sea ice during springtime bromine explosion events, whereas iodine emission is attributed to biological communities in the open ocean and hosted by sea ice. It has been previously demonstrated that bromine and iodine are present in Antarctic ice over glacial–interglacial cycles. Here we investigate seasonal variability of bromine and iodine in polar snow and ice, to evaluate their emission, transport and deposition in Antarctica and the Arctic and better understand potential links to sea ice. We find that bromine and iodine concentrations and Br enrichment (relative to sea salt content) in polar ice do vary seasonally in Arctic snow and Antarctic ice. Although seasonal variability in halogen emission sources is recorded by satellite-based observations of tropospheric halogen concentrations, seasonal patterns observed in snowpack are likely also influenced by photolysis-driven processes. Peaks of bromine concentration and Br enrichment in Arctic snow and Antarctic ice occur in spring and summer, when sunlight is present. A secondary bromine peak, observed at the end of summer, is attributed to bromine deposition at the end of the polar day. Iodine concentrations are largest in winter Antarctic ice strata, contrary to contemporary observations of summer maxima in iodine emissions. These findings support previous observations of iodine peaks in winter snow strata attributed to the absence of sunlight-driven photolytic re-mobilisation of iodine from surface snow. Further investigation is required to confirm these proposed mechanisms explaining observations of halogens in polar snow and ice, and to evaluate the extent to which halogens may be applied as sea ice proxies.

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50

Custard, K. D., C. R. Thompson, K. A. Pratt, P. B. Shepson, J. Liao, L. G. Huey, J. J. Orlando, et al. "The NOx dependence of bromine chemistry in the Arctic atmospheric boundary layer." Atmospheric Chemistry and Physics 15, no. 18 (September 29, 2015): 10799–809. http://dx.doi.org/10.5194/acp-15-10799-2015.

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Abstract. Arctic boundary layer nitrogen oxides (NOx = NO2 + NO) are naturally produced in and released from the sunlit snowpack and range between 10 to 100 pptv in the remote background surface layer air. These nitrogen oxides have significant effects on the partitioning and cycling of reactive radicals such as halogens and HOx (OH + HO2). However, little is known about the impacts of local anthropogenic NOx emission sources on gas-phase halogen chemistry in the Arctic, and this is important because these emissions can induce large variability in ambient NOx and thus local chemistry. In this study, a zero-dimensional photochemical kinetics model was used to investigate the influence of NOx on the unique springtime halogen and HOx chemistry in the Arctic. Trace gas measurements obtained during the 2009 OASIS (Ocean – Atmosphere – Sea Ice – Snowpack) field campaign at Barrow, AK were used to constrain many model inputs. We find that elevated NOx significantly impedes gas-phase halogen radical-based depletion of ozone, through the production of a variety of reservoir species, including HNO3, HO2NO2, peroxyacetyl nitrate (PAN), BrNO2, ClNO2 and reductions in BrO and HOBr. The effective removal of BrO by anthropogenic NOx was directly observed from measurements conducted near Prudhoe Bay, AK during the 2012 Bromine, Ozone, and Mercury Experiment (BROMEX). Thus, while changes in snow-covered sea ice attributable to climate change may alter the availability of molecular halogens for ozone and Hg depletion, predicting the impact of climate change on polar atmospheric chemistry is complex and must take into account the simultaneous impact of changes in the distribution and intensity of anthropogenic combustion sources. This is especially true for the Arctic, where NOx emissions are expected to increase because of increasing oil and gas extraction and shipping activities.

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Journal articles on the topic 'Halogeny'

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