Positive Halogen Research Articles

Lattice Matching and Halogen Regulation for Synergistically Induced Uniform Zinc Electrodeposition by Halogenated Ti3C2 MXenes

Dendrite growth and low Coulombic efficiency caused by uneven diffusion and electrodeposition of Zn2+ ions have emerged as a barrier to exploit the Zn metal anode. In this work, we demonstrate the stoichiometric halogenated MXenes (Ti3C2Cl2, Ti3C2Br2, and Ti3C2I2) as an artificial layer that can induce the uniform Zn deposition. The efficient redistribution effect results from the coherent heterogeneous interface reconstruction and regulated ion tiling by halogen surficial termination. The synergetic effects of high lattice matching (90%) between the adopted MXenes and Zn, as well as the positive halogen regulation, Zn2+ ions are guided to nucleate uniformly on the most extensive (000l) crystal plane of the MXene matrix and grow in a planar manner. In terms of Zn ion regulation, Cl termination is found to be more effective than O/F, Br, and I due to its moderate adsorption and diffusion coefficiency for Zn2+ ions. The Ti3C2Cl2-Zn anode achieves a life extension of over 12 times (840 h at 2 mA cm-2//1 mAh cm-2) over that of the bare Zn anode and serves more than 9000 cycles in a battery with a Ti3C2I2 cathode at a high rate of 3 A g-1. Given the abundance of lattice parameters and terminations of MXene materials, the developed strategy is expected to be extended to other metal anode systems.

Microanalysis of Cl, Br and I in apatite, scapolite and silicate glass by LA-ICP-MS

Constraining the abundance and distribution of halogens in geological materials has the potential to provide novel insights into a broad range of earth system processes (e.g. metasomatism, melting, volatile cycling and ore formation). In this contribution we develop analytical protocols for the in situ measurement of Cl, Br and I in widely distributed standard reference materials (apatite, scapolite, silicate glass) using readily available laser ablation ICP-MS instrumentation. Ablations were performed at a range of square spot sizes (30–80 μm) using a high repetition rate (25 Hz) and extended analyte dwell times (up to 250 ms) to improve sensitivity and signal stability. A comparison of LA-ICP-MS results with published halogen data was used to calculate the following theoretical limits of quantification; Cl = 360 μg/g, Br = 8 μg/g, I = 0.75 μg/g. A detailed assessment of raw signal intensities for different matrices with known halogen contents, combined with high resolution mass scans, provides new constraints on the origin of apparent halogen signals: on mass 35Cl signal excesses are likely 16O18OH and/or 17O18O; 79Br is influenced by peak shoulder overlap from 40Ar40Ar (a diargon cation, Ar2+2) and a matrix-based interference (159Tb2+) for samples with Br/Tb < 0.6; 127I signals are similar for all but the highest I materials analysed here, suggesting the presence of ubiquitous gas-based interferences. The observation that false positive halogen signals only occur during sample ablation suggests that they are either matrix derived or related to the process of sample introduction. During ablation, matrix loading may reduce plasma energy, resulting in a greater proportion of polyatomic interferences in the system. For Cl, we provide a new time dependent excess apparent Cl spline correction defined by analysis of halogen-free olivine via a modified version of the Iolite Data Reduction Scheme ‘X_Trace_Elements_IS’. The correction improves the limit of linearity to ~100 μg/g for Cl in glasses down to a 38 μm spot size. We test our methodology on apatite from Permian alkaline lamprophyres in the Pyrenees (Spain) and quartz-hosted melt inclusions from rhyolitic deposits at the Taupo volcanic zone (New Zealand), obtaining results comparable to electron microprobe and SIMS data. We provide recommendations for analytical best practice and highlight the need for well characterised matrix matched SRMs spanning a broad range of concentrations to allow for the identification and removal of non-analyte related contributions to measured signals.

A Copper Halide Promoted Regioselective Halogenation of Coumarins Using N-Halosuccinimide as Halide Source

A safe, convenient, and regioselective synthesis of 3-halo coumarins using a metal halide (CuX2 alone or with ZnX2) promoted halogenation with N-halosuccinimide (NXS) as halide source is reported. The synthesis involved the steady in situ generation of highly reactive positive halogen (X+) by the coordination of copper or zinc with the N-halosuccinimide and subsequent electrophilic aromatic substitution of the electron-deficient coumarins. This procedure works well also for the halogenation of less electron-rich naphthoquinones, flavones, and methoxypsoralen in moderate to quantitative yields. This protocol features simple experimental conditions using readily available inexpensive reagents and provides a convenient approach to the chlorination or bromination of some useful heteroaromatic compounds.

A comparative study of model halogen-bonded, π-hole-bonded and cationic complexes involving NCX AND H2O (X = F, Cl, Br)

A MP2/6-311+ +G(d,p) study of NCX (X = F, Cl, Br) has shown that it is possible to attach an electrophile (H+, Be2+) to the positive halogen X surface of NCX. The stability and properties of model halogen-bonded and π-hole carbon-bonded NCX/H2O complexes were found to be significantly affected by H+ or Be2+ cationic attachment at the N atom. The halogen-bonded complexes are destabilised by binding at the N, while an attached proton enhances the binding in the π-hole bonded dimers. For the attached Be2+, an unusual complex was obtained with the NCF subunit, whereas the complexes containing Cl and Br were destabilised by the interaction.

Solvolysis of 4-Halogeno-4-Alkyl-2,6-di-tert-butylcyclohexa-2,5-dienones Induced by Positive Halogen Donors as Electrophiles

Positive halogen donors such as N-iodosuccinimide (NIS) induce solvolysis of dienones 1, as model 4-halogenocyclohexa-2,5-dienones, in different hydroxylic solvents (ROH), yielding the 4-RO-cyclohexa-2,5-dienones (2). The rate of the solvolysis with NIS is highly dependent on the structure of ROH. The problem of such dependency is overcome by running the reaction in ROH diluted with MeCN, a polar aprotic solvent, in place of pure ROH; the rate of the reaction in the ROH-MeCN solvent mixture is almost independent of the structure (or the polarity) of ROH, and the reaction is completed faster or markedly faster than in neat ROH. The results suggest that the solvolysis rate is controlled by the polarity of the solvent system, although the hydrogen-bond acceptability of MeCN for dilution also accelerates the reaction. A mechanism for the solvolysis is proposed, involving electrophilic attack of a positive halogen donor at the halogen atom of 1, generating the 4-oxocyclohexa-2,5-dienyl cation intermediates (8) via the rate-limiting polar transition states.

ChemInform Abstract: A Novel Method for the Conversion of Halide Anion to the Positive Halogen by Nitrobenzenesulfonyl Peroxide. Application to Oxyhalogenation of Olefin.

Bromide and chloride anions could be readily oxidized into positive halogens by treating with p-nitrobenzenesulfonyl peroxide. The positive halogens, thus formed, reacted with olefins to give epihalonium ions, which were trapped by oxygen nucleophiles inter- or intramolecularly to afford oxyhalogenated compounds.

ChemInform Abstract: Simple and Practical Halogenation of Arenes, Alkenes, and Alkynes with Hydrohalic Acid/H2O2 (or TBHP).

Abstract A simple protocol for the halogenation of arenes utilizing a combination of aqueous hydrogen peroxide (34 %) or tert-butylhydroperoxide (70 %) and hydrohalic acid is presented. A similar procedure of oxyhalogenation involving the in situ generation of positive halogen reagents is applied for the preparation of vicinal trans-dibromoalkanes and dichloroalkanes from alkenes. The reaction of alkenes with a combination of hydrochloric acid and hydrobromic acid with hydrogen peroxide gave a mixture of 1-bromo 2-chloro alkanes and 1,2-dibromoalkanes. Oxidative bromination of alkynes is also reported under similar conditions.

4-Aryl(benzyl)sulfonyl-2-chloro-5-polyfluoroalkyl-1,2,3-triazoles. The first monocyclic N-chloro-1,2,3-triazoles

Treatment of 4-aryl(benzyl)sulfonyl-5-polyfluoroalkyl-v-triazoles with NaOCl gave the 4-aryl(benzyl)-sulfonyl-2-chloro-5-polyfluoroalkyl-v-triazole derivatives which contain a chlorine atom only on the N(2) atom of the heterocycle. The structure of 2-chloro-5-(1,1,2,2,3,3-hexafluoropropyl)-4-(p-tolyl-sulfonyl)-2H-[1,2,3]triazole has been established by X-ray structural investigation. The presence of a highly polarized N—Cl bond with a positive halogen atom causes the N-chlorotriazoles to react with KCN and KF as strong acids to form the potassium salts of the triazoles and to form 4-arylsulfonyl-2-(2-chloro-1-ethoxyethyl)-5-polyfluoroalkyl-2H-[1,2,3]triazoles with vinyl ethyl ether. It was found that chlorination of 4-arylsulfonyl-5-polyfluoroalkyl-v-triazoles in the presence of KF gives 4-chloro-5-polyfluoroalkyl-2H-[1,2,3]triazoles.

N-Bromonicotinamide- A novel, stable and less expensive oxidant and its antimicrobial activity

N-Bromonicotinamide (NBN) is prepared by standard procedure and characterized. It is found to be a stable and mild oxidant of low cost. It is prepared by a simple method, giving high yield in a short period of time. The condition and the experimental set up are also very easy to follow. Its formal redox potential shows NBN can be used as effective source of positive halogen. It will be a valuable addition to the existing oxidants. It is screened for antibacterial activity against E. coli, Salmonella enterocolitica, Shigella flexneri and Staphylococcus aures at various concentrations using disc diffusion method.

ESD thresholds for NaCl

Energy thresholds of electron stimulated desorption (ESD) for thin NaCl layers relative to the target current onset are measured. The applied procedure allows to correct electron beam energy for the contact potential difference in the system. The measured threshold energies are about 16.8 and 21 eV for Cl +. For Na +, Na and Cl the threshold energies are about 8.4 and 16.8 eV. The value of 8.4 eV coincides with the fundamental absorption edge and confirms the so-called “defect-mediated desorption” model of ESD. Basing on the experimental fact that the fundamental absorption edge appears to be a common threshold for different particles it is suggested that the near surface lattice instabilities induced by electronic transitions may result in a direct ejection of the constituents as well. The 16.8 eV threshold for Cl + confirms the involvement of an Auger transition in positive halogen ion emission. The 21 eV threshold is assigned to the shake-up/shake-off processes.

ESD thresholds for KCl

AbstractElectron stimulated desorption (ESD) energy thresholds for thin KCl layers are measured relative to the target current onset. The applied procedure allow to correct electron beam energy for the contact potential difference in the system. The results show that the energy threshold for ESD of cations and anions (or neutral Cl) coincides with the fundamental absorption edge. The measured threshold energies are about 20 eV for Cl+ and about 8 eV for K+ and Cl (or Cl−) ESD. The 20 eV threshold for Cl+ signal confirms the involvement of an Auger transition in positive halogen ion emission while the 8 eV threshold for the other species is consistent with the so‐called “defect‐mediated desorption” model of ESD. It is proposed that the near surface lattice instability induced by electronic transition results in a local heating capable of ejecting constituent ion or neutral atom.

Iodine as a Chemoselective Reoxidant of TEMPO: Application to the Oxidation of Alcohols to Aldehydes and Ketones

[reaction: see text] Chemoselective alcohol oxidations using catalytic TEMPO and stoichiometric iodine as the terminal oxidant were studied. Iodine was compared to other positive halogens as the terminal oxidant and shown to be superior in cases of electron-rich and heteroaromatic rings. The new conditions were successfully applied to an important intermediate (2) in the synthesis of Losartan.

Unusual Oxidation of 4‐Amino‐4H,8H‐bisfurazano[3,4‐b:3′,4′‐e]pyrazines.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Kinetics and mechanism of condensation reactions of thiobenzamides and N-substituted thioureas

The condensation reaction of thiobenzamides and of N-substituted thioureas in dimethyl sulfoxide or in methanol, in the presence of the mixture DMSO–H+–X− (X = Cl, Br) produces 1,2,4-thiadiazole derivatives. Kinetic investigation emphasizes the importance of the presence of dimethyl sulfoxide, of halide ions and of an acidic catalyst. For reactions of thiobenzamide, the bromide ion increases the reaction rate 150 times more than the chloride ion. The presence of electron-donating groups on the starting thioamidic group enhances the reactivity. Reported data indicate that the mixture DMSO–H+–X− produces a positive halogen species. The proposed mechanism involves the formation of the N-halogenated thioamides (or N-substituted thioureas) in the rate-determining step. The reactivity of thionicotinamide S-oxide is also reported and discussed.

Unusual oxidation of 4-amino-4 H,8 H-bisfurazano[3,4-b:3’,4’- e]pyrazines

The oxidation of 4,8-diamino-4H,8H-bisfurazano[3,4-b:3',4'-e]pyrazine1with positive halogen reagents and related oxidants afforded a stable nitrogen-centered radical, bisfurazano[3,4-b:3',4'-e]pyrazine biradical4; tetrazene2was a probable intermediate.

DIFFÉRENCE DE COMPORTEMENT ENTRE LES RÉACTIFS ELECTROPHILES DIÉTHYLTRICHLOROMÉTHYLPHOS- PHONATE ET TÉTRACHLORURE DE CARBONE OPPOSÉS AU TRIÉTHYLPHOSPHITE

The reaction of triethylphosphite 1 with diethyltrichloromethylphosphonate 2b in the absence of solvents and catalysts yields mainly diethyl(1,1-dichloropropyl)phosphonate 4 and diethyldichloromethylphosphonate 7. These main products are accompanied by a variety of by-products which differ considerably from those obtained in the reaction between triethyl phosphite and CCl4. Both reactions would begin by a halophilic substitution of triethylphosphite on the positive halogen. For diethyltrichloromethylphosphonate 2b the formed carbanion would then attack preferentially the carbon β to P+ and the hydrogen γ to P+ on heterophosphonium cation. In contrast, the less sterically hindered trichloromethyl carbanion formed by the halophilic attack of triethylphosphite on carbon tetrachloride would rather attack mainly the positive P+ of this cation. The tetraethyl(dichloromethylene)bisphosphonate 8 previously reported by Kukhar and Sagina to be the main product formed in the thermal reaction between triethylphosphite and diethyltrichloromethylphosphonate was not found under our conditions. We observed its formation only under photochemical irradiation.

Simple and practical halogenation of arenes, alkenes and alkynes with hydrohalic acid/H 2O 2 (or TBHP)

A simple protocol for the halogenation of arenes utilizing a combination of aqueous hydrogen peroxide (34 %) or tert-butylhydroperoxide (70 %) and hydrohalic acid is presented. A similar procedure of oxyhalogenation involving the in situ generation of positive halogen reagents is applied for the preparation of vicinal trans-dibromoalkanes and dichloroalkanes from alkenes. The reaction of alkenes with a combination of hydrochloric acid and hydrobromic acid with hydrogen peroxide gave a mixture of 1-bromo 2-chloro alkanes and 1,2-dibromoalkanes. Oxidative bromination of alkynes is also reported under similar conditions.

ChemInform Abstract: The First Reagent‐Controlled Asymmetric Halolactonizations. Dihydroquinidine—Halogen Complexes as Chiral Sources of Positive Halogen Ion.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Addition of Electrophiles to Unsymmetric Alkenes. Effects of β Oxygen Substituents on the Stereo‐ and Regiochemistry of Positive Halogen Addition

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The first reagent-controlled asymmetric halolactonizations. Dihydroquinidine-halogen complexes as chiral sources of positive halogen ion

The first reagent-controlled asymmetric halolactonizations are described. Complexes of I+ with O-acyl- and O-aryldihydroquinidines are used to promote the asymmetric halolactonization of prochiral θ, δ-unsaturated carboxylic acids with low but measurable and reproducible enantioselectivity. Experimental factors affecting the ee's are described. Key words: halocyclization, halogenation, halonium ions, chiral, stereoselective.