Elemental Bromine Research Articles

Halogenation of diphosphane dichalcogenides

GRAPHICAL ABSTRACT

Elemental Bromine Production by TiO2 Photocatalysis and/or Ozonation.

Significant production of elemental bromine (Br2 ) was observed for the first time when treating bromide containing solutions at acidic pH, with TiO2 photocatalyst, ozone, or a combination thereof. Br2 selectivities up to approximately 85 % were obtained and the corresponding bromine mass balance values satisfied. The process is general and may be applied at a laboratory scale for green bromination reactions, or industrially as a cheap, safe, and environmentally sustainable alternative to the currently applied bromine production methods.

Elemental Bromine Production by TiO2 Photocatalysis and/or Ozonation

AbstractSignificant production of elemental bromine (Br2) was observed for the first time when treating bromide containing solutions at acidic pH, with TiO2 photocatalyst, ozone, or a combination thereof. Br2 selectivities up to approximately 85 % were obtained and the corresponding bromine mass balance values satisfied. The process is general and may be applied at a laboratory scale for green bromination reactions, or industrially as a cheap, safe, and environmentally sustainable alternative to the currently applied bromine production methods.

Conjugate halo- and mercuroazidation of 1-phenyltricyclo-[4.1.0.02.7]heptane. Synthesis of a conformationally rigid α-amino acid with a bicyclo[3.1.1]heptane skeleton

1-Phenyltricyclo[4.1.0.02.7]heptane reacted with N-bromo-, N-chloro-, and N-iodosuccinimides and with mercury(II) acetate in the presence of sodium azide as external nucleophile to give conjugate addition products to the central C1–C7 bicyclobutane bond with a norpinane structure, where the azido group and the phenyl were attached to the same carbon atom (C6). The bromo- and chloroazidation showed anti-stereo-selectivity, and the iodoazidation, moderate syn-stereoselectivity; the mercuroazidation afforded exclusively the corresponding syn-addition product. Hydro-, bromo- and chlorodemercuration of the mercury adduct with sodium tetrahydridoborate and elemental bromine and chlorine, respectively, did not involve the azido group, and the original configuration was retained. The reduction of the hydrodemercuration product with LiAlH4 gave 6-exo-phenylbicyclo[3.1.1]heptan-6-amine which was transformed in three steps into conformationally rigid 6-endo-(acetamido)bicyclo[3.1.1]heptane-6-carboxylic acid.

Unusual traits of cis and trans-2,3-dibromo-1,1-dimethylindane on the way from 1,1-dimethylindene to 2-bromo-, 3-bromo-, and 2,3-dibromo-1,1-dimethylindene.

Do not rely on the widely accepted rule that vicinal, sp3-positioned protons in cyclopentene moieties should always have more positive 3J NMR coupling constants for the cis than for the trans arrangement: Unrecognized exceptions might misguide one to wrong stereochemical assignments and thence to erroneous mechanistic conclusions. We show here that two structurally innocent-looking 2,3-dibromo-1,1-dimethylindanes violate the rule by means of their values of 3J(cis) = 6.1 Hz and 3J(trans) = 8.4 Hz. The stereoselective formation of the trans diastereomer from 1,1-dimethylindene was improved with the tribromide anion (Br3−) as the brominating agent in place of elemental bromine; the ensuing, regiospecific HBr elimination afforded 3-bromo-1,1-dimethylindene. The addition of elemental bromine to the latter compound, followed by thermal HBr elimination, furnished 2,3-dibromo-1,1-dimethylindene, whose Br/Li interchange reaction, precipitation, and subsequent protolysis yielded only 2-bromo-1,1-dimethylindene.

Bromine-rich Zinc Bromides: Zn6Br12(18-crown-6)2×(Br2)5, Zn4Br8(18-crown-6)2×(Br2)3, and Zn6Br12(18-crown-6)2×(Br2)2.

The bromine-rich zinc bromides Zn6Br12(18-crown-6)2×(Br2)5 (1), Zn4Br8(18-crown-6)2×(Br2)3 (2), and Zn6Br12(18-crown-6)2×(Br2)2 (3) are prepared by reaction of ZnBr2, 18-crown-6, and elemental bromine in the ionic liquid [MeBu3N][N(Tf)2] (N(Tf)2 = bis(trifluoromethylsulfonyl)amide). Zn6Br12(18-crown-6)2×(Br2)5 (1) is formed instantaneously by the reaction. Even at room temperature, compound 1 releases bromine, which was confirmed by thermogravimetry (TG) and mass spectrometry (MS). The release of Br2 can also be directly followed by the color and density of the title compounds. With controlled conditions (2 weeks, 25 °C, absence of excess Br2) Zn6Br12(18-crown-6)2×(Br2)5 (1) slowly releases bromine with conconcurrent generation of Zn4Br8(18-crown-6)2×(Br2)3 (2) (in ionic liquid) and Zn6Br12(18-crown-6)2×(Br2)2 (3) (in inert oil). All bromine-rich zinc bromides contain voluminous uncharged (e.g., Zn3Br6(18-crown-6), Zn2Br4(18-crown-6)) or ionic (e.g., [Zn2Br3(18-crown-6)](+), [(Zn2Br6)×(Br2)2](2-)) building units with dibromine molecules between the Zn oligomers and partially interconnecting the Zn-containing building units. Due to the structural similarity, the bromine release is possible via crystal-to-crystal transformation with retention of the crystal shape.

Obtaining the Iodine Value of Various Oils via Bromination with Pyridinium Tribromide

A laboratory exercise was devised that allows students to rapidly and fairly accurately determine the iodine value of oleic acid. This method utilizes the addition of elemental bromine to the unsaturated bonds in oleic acid, due to bromine’s relatively fast reaction rate compared to that of the traditional Wijs solution method. This method also uses pyridinium tribromide as a bromine source in an effort to eliminate many of the safety hazards of working with elemental bromine. After the addition of a known quantity of bromine to the reaction flask, excess bromine is reduced with potassium iodide forming elemental iodine. The elemental iodine is then titrated with sodium thiosulfate and a starch indicator in a back-titration to determine the amount of excess bromine added to the oleic acid. Students then determine the iodine value of oleic acid by using a 126 g iodine/80 g of bromine ratio. This exercise can yield results fairly close to the accepted iodine value of 90 for oleic acid, as several of the gro...

Phosphanchalkogenide und ihre Metallkomplexe. III. Halogenierungsprodukte der Gold(I)komplexe Ph3PEAuX (E = S oder Se; X = Cl, Br oder I)

Abstract The complexes Ph3PEAuI (E = S, Se; 1, 2) were obtained from the reaction of Ph3PEAuCl with KI; they are appreciably less stable than their chloro and bromo analogues. The X-ray structures were determined, whereby 1 proved to be contaminated by a small amount of Ph3PS·I2. Oxidation of 1 and 2 with elemental iodine led to the adducts Ph3PEAuI·0.5I2 (3 and 4), but X-ray investigation of a crystal initially assumed to be 3 proved it to be a 1:1 mixture of 3 with the adduct Ph3PS·1.5I2, while in 4 the iodine molecule was severely disordered, which prevented successful refinement of the structure. Decomposition of 4 by loss of gold led to Ph3PSeI2·1.5I2 4a. Complexes Ph3PEAuX (E = S, Se; X = Br, Cl) were oxidized by elemental bromine (X = Br) or PhICl2 (X = Cl) to Ph3PEAuX 3 (5, 6, 9, 10); none of these X-ray structures could be refined satisfactorily because of diffuse scattering phenomena. Further oxidation led to the ionic compounds [Ph3PEX]+ [AuX 4]– (X = Br, E = S, Se: 7, 8; X = Cl, E = S, 11) or [Ph3PSeCl]+ 0.5[Au4Cl10Se2]2– (12), containing the novel groupings P–E–X. X-ray structures confirmed the nature of all four of these compounds, which display longer P–E bonds than the gold(I) starting materials and short X···X and/or E···X contacts between cations and anions.

Clay-Polymer Nanocomposite-Supported Brominating Agent

AbstractThe conventional methods of direct bromination of organic compounds with elemental bromine have several major drawbacks such as handling difficulty, corrosive effect, and toxicity, in addition to over-bromination and problems with isolation of products from the reaction mixture. Supported catalysts and reagents have become popular in the synthesis of organic chemicals over recent decades because they have overcome almost all of the drawbacks noted above. In the present study, a new clay polymer nanocomposite (CPN)-supported brominating agent was prepared from montmorillonite (Mnt) and styrene-co-vinyl pyridinium polymer. The reagent was obtained by the direct interaction of a two-fold excess of poly(styrene-co-N-methyl-4-vinylpyridinium) bromide with Na-montmorillonite (NaMnt) through ion exchange between Na+ of the NaMnt and pyridinium ions in the copolymer to provide CPN3 with free methylpyridinium bromide side chains. The structure of the CPN3 prepared was characterized by infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Treatment of the CPN3 with bromine using the bromide ions which remained led to the perbromide-supported reagent, CPN4. The activity of the resulting CPN4 brominating reagent was examined through direct bromination of some alkenes, arenes, and carbonyl compounds and compared with the effectiveness of a crosslinked polymeric perbromide reagent. The yields obtained from application of the reagent were moderate to excellent. The advantages of this reagent, such as stability at room temperature, ease of regeneration from the polymeric by-product, and the yields of the brominated products, confirm the viability of using a CPN-supported brominating agent as a reactive reagent in organic chemistry synthesis.

Uranyl Schiff base complexes as new heterogeneous catalysts for halogen exchange reactions between alkyl halides and elemental halogens

Mild and effective procedure for the halogen exchange reaction of alkyl halides with elemental iodine and bromine catalyzed with uranyl Schiff base complexes in various aprotic solvents was developed. Corresponding alkyl bromides and iodides were obtained with high yields within 20—70 min. The structures of the target products were confirmed by physical and spectroscopic data.

Quantum chemistry investigation on the reaction mechanism of the elemental mercury, chlorine, bromine and ozone system.

Ab initio calculations were performed to study the quantum chemistry reactions mechanisms among Hg(0), elemental halogen and O3. The geometry of reactions, transition states (TS), intermediates (M) and products were optimized using the MP2 method at the SDD basis function level for Hg, and using 6-311++G (3df, 3pd) for other species. Molecular energies were calculated at QCISD (T) level with zero point energy. Activation energies were calculated along with pre-exponential factors . The reaction rate constants within 298-1800K were calculated according to transition state theory (TST). The influences of O3 on the reaction of Hg(0) with halogen are discussed. Hg(0) can be oxidized to Hg(1+) by halogen and O3, and halogen and O3 can be arranged in decreasing order as: Br2 > BrO > O3 > Br > Cl, BrCl > HBr > HCl, Br2 > Cl2 according to reaction rate constants. When O3 is presented, Br2, HBr, BrCl, Cl2 and HCl react with O3 and are initially converted to BrO and ClO. O3 is unfavorable for oxidation of Hg(0) by Br2. The mixture of HBr and O3 has better oxidizing Hg(0) performance than HBr and O3. Cl is less effective than Br for oxidation of Hg(0).

Role of Bromide in Hydrogen Peroxide Oxidation of CTAB-Stabilized Gold Nanorods in Aqueous Solutions

In recent years hydrogen peroxide has often been used as the oxidizing agent to tune the resonance wavelength of gold nanorods (AuNRs) through anisotropic shortening in the presence of cetyltrimethylammonium bromide (CTAB). However, a complete picture of the reaction mechanism remains elusive. In this work, we present a systematic study on the mechanism of the AuNR oxidation by revealing the important role of bromide. Hydrogen peroxide slowly oxidizes bromide into elemental bromine. The latter two form tribromide, which exhibits a characteristic 272 nm absorption peak. The peak intensity, representing the concentration of tribromide, is found to have a linear correlation with the oxidation rate of AuNRs. Tribromide approaches AuNRs through conjugating strongly with CTA cationic micelles, which leads to the oxidation occurring on the surface of AuNRs. In contrast, the CTA micelles protect AuNRs from the direct oxidation by hydrogen peroxide. Our findings are believed to provide new insights into the reaction mechanism occurring in the relevant CTAB-AuNR systems, which can be important for understanding the principles governing the reaction dynamics.

Synthesis, molecular structures, Mössbauer and electrochemical investigation of ferrocenyltelluride derivatives: (Fc2Te2)Fe(CO)3I2 [(CO)3IFe(μ-TeFc)]2, CpFe(CO)2TeFc, CpFe(CO)2TeX2Fc (X = Br, I) and CpFe(CO)2(μ-TeFc)Fe(CO)3I2

Depending on the ratio of the starting reagents, the interaction of [FcTeI] with Fe(CO)5 gave complex (Fc2Te2)Fe(CO)3I2 (1) bearing an Fc2Te2 ligand, or a dimeric complex [(CO)3IFe(μ-TeFc)]2 (2). An interaction of equimolar amounts of [CpFe(CO)2]2 and Fc2Te2 under the thermal conditions in toluene afforded CpFe(CO)2TeFc (3). Complex 3 can be easily halogenated at the Te center by elemental bromine and iodine to give monomeric CpFe(CO)2TeX2Fc (X = Br (4), I (5)). Complex 5 can be prepared alternatively via formal insertion of [FcTeI] into Fc–I bond of CpFe(CO)2I. Complex 3 readily substitutes one carbonyl in Fe(CO)4I2 to give the adduct CpFe(CO)2(μ-TeFc)Fe(CO)3I2 (6).

ChemInform Abstract: 8‐Bromination of 2,6,9‐Trisubstituted Purines with Pyridinium Tribromide.

AbstractA convenient procedure for the 8‐bromination of electron‐rich trisubstituted purines using pyridinium tribromide, a crystalline alternative reagent to elemental bromine, is presented.

Determination of Acrylamide and Acrolein in Smoke from Tobacco and E-Cigarettes

Acrylamide and acrolein are two short-chained hazardous compounds with neurotoxic, carcinogenic, and mutagenic effects. The aim of this paper is to describe a fast and simple procedure for simultaneous determination of both acrylamide and acrolein under standard conditions, suggest a suitable calibration protocol for custom analysis, and demonstrate its applicability to the analysis of gaseous products from, e.g., cigarettes, cigars, or electronic cigarettes. A gas chromatography–mass spectrometry (GC–MS) method was developed to quantify acrylamide and acrolein in smoke vapor from electronic cigarettes, tobacco cigarettes, and cigars. Nonionic and highly polar molecules with a low boiling point and molecular mass need a suitable derivatization method to achieve appropriate retention and selectivity on commonly used relatively nonpolar stationary phases and to enhance the molecular mass for easy MS detection. The derivatization of acrylamide and acrolein was carried out by a bromination method with elemental bromine. The dibromo derivatives were extracted into an organic solvent and following a dehydrobromination procedure the samples were injected into the GC–MS system. Important experimental parameters were varied, after which the bromination time was defined as 30 min, and the injector temperature and the starting temperature of gradient were set at 280 and 50 °C respectively. Acrolein was found in all tested samples, while acrylamide was detected only in smoke from normal tobacco. Possible mechanisms for the formation of these unsaturated compounds in the samples are discussed. After its validation the newly developed method was successfully and reliably applied to the analysis of both compounds. This short method provides an easy way to determine acrylamide and acrolein in gaseous samples.

Synthesis and characterization of Au(I) and Au(III) complexes containing N-heterocyclic ligands derived from amino acids

A series of [Au(NHC)2] (1a–4a) complexes supported by NHC ligands derived from glycine, alanine, methionine and phenylalanine (1–4 respectively) were prepared via a direct transmetalation reaction of their respective silver complexes. The Au complexes were characterized by ESI-MS and NMR spectroscopy in solution. These compounds exhibit instability when the solvent is removed; they displayed a strong tendency to form colored solutions in the order 4a>3a>2a>1a, which is associated with gold nanoparticles. 1a and 2a undergo oxidative addition of elemental bromine, yielding [Au(NHC)2Br2] (1b) for 1a and a mixture of [Au(NHC)2Br2] (2b) and [Au(NHC)Br3] (2c) for 2a. 2b and 2c were characterized by single crystal X-ray diffraction.

An underrated cheap Lewis acid: Molecular bromine as a robust catalyst for bis(indolyl)methanes synthesis

A discovery that inexpensive elemental bromine can act as a potent Lewis acid catalyst is disclosed. Under the catalysis of only 2mol% of Br2, indoles reacted rapidly with carbonyl compounds to give bis(indolyl)methanes with extremely high efficiency and wide substrate scope. Moreover, a Br2-catalyzed aqueous-phase reaction is also presented to further demonstrate the power of this novel catalyst.

Betting On Bromine In Arkansas

More than a mile under the ground in the southwestern corner of Arkansas lies a resource unique in the U.S.: salty brines rich in bromine. Seaweed and plankton that decomposed during the Jurassic period 200 million years ago, when the region was under the sea, left behind bromine in concentrations of 5,000 to 6,000 parts per million, about 85 times greater than that of ocean water. The brines came to light in the 1920s when oil companies encountered them while drilling in the area. Although they were considered a nuisance at first, their commercial potential gradually became apparent. In 1957, production of elemental bromine commenced in Arkansas via a process in which bromine salts are reacted with chlorine. Although other sources of bromine have sprung up since then, Arkansas is still the source of about a quarter of the world’s supply. It’s produced by two chemical companies, Albemarle and Chemtura, ...

8-Bromination of 2,6,9-trisubstituted purines with pyridinium tribromide

2,6,9-Trisubstituted purines are brominated in high yields using pyridinium tribromide as the brominating reagent. This procedure works excellently for electron-rich purines having electron-donating substituents at the 2- and 6-positions. The use of pyridinium tribromide, a crystalline alternative to elemental bromine, improves the bromination procedure for this type of substrate as the reagent is easy to handle and the work-up and purification procedures are simplified.

Brominations with Pr4NBr9 as a Solid Reagent with High Reactivity and Selectivity­

Tetrapropylammonium nonabromide (Pr4NBr9) is introduced as a room-temperature solid reagent for rapid bromination reactions of various substrates. The reagent exhibits reactivity similar to that of elemental bromine, but shows higher selectivity and it is easier and safer to store and to handle.