Revisiting the Bromination of CH Bonds with Molecular Bromine by Using a Photo‐Microflow System

The photobromination of C?H bonds by using molecular bromine was reinvestigated under microfluidic conditions. The continuous‐flow method suppressed the production of dibrominated compounds and effectively produced the desired monobrominated products with high selectivity. Rapid bromination of benzylic substrates containing a photoaffinity azide group was achieved without any decomposition.     

Properties of Bromine Fused Salts Based on Quaternary Ammonium Molecules and Their Relevance for Use in a Hydrogen Bromine Redox Flow Battery

Bromine complexing agents (BCA) in aqueous electrolytes for hydrogen bromine flow batteries are used to reduce bromine‘s vapour pressure, while an insoluble and liquid fused salt is formed. The properties (concentrations, composition, conductivity and viscosity) of this fused salt are investigated in this study systematically ex situ by using 7 BCAs at different state of charge in HBr/Br₂/H₂O electrolytes with a theoretical capacity of 179.6 Ah L⁻¹. Bromine is stored in the fused salt at concentrations up to 13.6 M, reaching theoretical volumetrical capacities up to 730 Ah L⁻¹ in fused salts. The fused salt consists of a pure, bromine- and water-free ionic liquid of organic [BCA]⁺ cations and polybromides, and its conductivity bases on a hopping mechanism among the polybromides. Alkyl side chain length of the BCAs and distribution of polybromides influence strongly the conductivity and viscosity of the fused salts. 1-ethylpyridin-1-iumbromide results to be favoured BCA for application.     

3‐Formylpyrroles from 3‐Furfurylamines by Bromine Oxidation Reaction

Oxidation of 3‐furfurylamines 3a‐e with bromine in acetone‐water solution gave N‐substituted 3‐formylpyrroles 4a‐e in good yields. A reaction mechanism via the Clauson‐Kaas reaction followed by the cis‐trans isomerization of the 2‐ene‐1,4‐diones 13 and 14 was proposed to account for the formation of the pyrroles 4a‐e .     

Copper(II) Complexes of a Hexadentate Mixed‐Donor N3S3 Macrobicyclic Cage: Facile Rearrangements and Interconversions

The potentially hexadentate mixed‐donor cage ligand 1‐methyl‐8‐amino‐3,13,16‐trithia‐6,10,19‐triazabicyclo[6.6.6]eicosane (AMME‐N₃S₃sar; sar=sarcophagine) displays variable coordination modes in a complex with copper(II). In the absence of coordinating anions, the ligand adopts a conventional hexadentate N₃S₃ binding mode in the complex [Cu(AMME‐N₃S₃sar)](ClO₄)₂ that is typical of cage ligands. This structure was determined by X‐ray crystallography and solution spectroscopy (EPR and NIR UV/Vis). However, in the presence of bromide ions in DMSO, clean conversion to a five‐coordinate bromido complex [Cu(AMME‐N₃S₃sar)Br]⁺ is observed that features a novel tetradentate (N₂S₂)‐coordinated form of the cage ligand. This copper(II) complex has also been characterized by X‐ray crystallography and solution spectroscopy. The mechanism of the reversible interconversion between the six‐ and five‐coordinated copper(II) complexes has been studied and the reaction has been resolved into two steps; the rate of the first is linearly dependent on bromide ion concentration and the second is bromide independent. Electrochemistry of both [Cu(AMME‐N₃S₃sar)]²⁺ and [Cu(AMME‐N₃S₃sar)Br]⁺ in DMSO shows that upon reduction to the monovalent state, they share a common five‐coordinated form in which the ligand is bound to copper in a tetradentate form exclusively, regardless of whether a six‐ or five‐coordinated copper(II) complex is the precursor.     

Probing the Ignored Elimination Channel of Br2 in the 248 nm Photodissociation of 1,1‐Dibromoethylene by Cavity Ring‐Down Absorption Spectroscopy

A process of elimination : Optical spectra of the Br₂ product eliminated from the photodissociation of 1,1‐dibromoethylene at 248 nm are obtained (see picture), and the subsequent dissociation pathways are proposed with the aid of ab initio potential energy calculations. The behavior of the compound is compared with that of 1,2‐dibromoethylene.

     

N.Br halogen bonding: one-dimensional infinite chains through the self-assembly of dibromotetrafluorobenzenes with dipyridyl derivatives

The N.Br halogen bonding drives the self-assembly of 1,4-dibromotetrafluorobenzene (1 a) and its 1,3 or 1,2 analogues (1 b,c, respectively) with dipyridyl derivatives 2 a,b. The isomeric supramolecular architectures 3 a-f are obtained as cocrystals that are stable in the air at room temperature. The solid-state features of these 1D infinite chains 3 have been fully characterized by single-crystal X-ray, Raman, and IR analyses. The occurrence of N.Br halogen bonding in solution has been detected with (19)F NMR spectroscopy. The N.Br halogen bonding is highly selective and directional and the geometry of the single strands of noncovalent copolymers 3 is programmed by the geometry of halogen-bonding donor and acceptor sites on the starting modules. The composition and topology of the instructed networks can be predicted with great accuracy. Experiments of competitive cocrystal formation established the strength of the N.Br interaction relative to other halogen bondings and the ability of different modules 1 to be involved in site-selective supramolecular syntheses.     

Structure of exo,exo-2,3-endo,endo-5,6-tetrabromobicycloheptane

The X-ray crystal structure analysis of the title compound, exo,exo-2,3-endo,endo-5,6-tetrabromobicycloheptane, C₇H₈Br₄, which is a product of high temperature bromination of norbornadiene, shows that the skeleton of the molecule is not changed after two bromine molecules are added via successive bromination reactions. The addition of Br₂ to both double bonds occurs (contrary to our expectation) in a syn fashion. It crystallizes in the orthorhombic space group Pbca with a = 15.688(2), b = 13.345(2), c = 9.461(1) Å, V = 1980.7(3) ų, Z = 8 and Dx = 2.762 gcm^–3.     

溴水氧化氰根光度法测定微量氰化物

在磷酸介质中,氰根被饱和溴水氧化为溴化氰,剩余的溴水用磺基水杨酸除去。溴化氰与碘化钾反应生成单质碘,碘与淀粉显色,从而测定氰化物。其最大吸收波长λｍ ａｘ＝ ５６５ｎｍ ,ＣＮ－ 在０～１５μｇ／２５ｍ Ｌ范围内呈良好线性关系,表观摩尔吸光系数为３．１×１０４Ｌ·ｍ ｏｌ－ １·ｃｍ － １。已用于测定废水中的氰化物。     

四川白皎无烟煤对碘和溴的吸附特征

四川白皎无烟煤对碘和溴的吸附特征徐龙君刘成伦鲜学福张代钧（重庆大学资源及环境工程学院重庆４０００４４）关键词煤，吸附，碘，溴，动力学方程碘是煤液化的有效催化剂，煤也能吸附一定量的碘，因而使得人们对煤吸附碘的研究产生了浓厚的兴趣［１～４］。以往的研究...