Addition Reaction Of Bromine Research Articles

Thermal properties and bromine addition reaction of ionic liquids containing vinyl-substituted bis-sulfonylamide anion

Ionic liquids (ILs) comprising alkylammonium cations and a bis(sulfonyl)amide anion with a vinyl substituent (SO2CF3-N–-SO2CH = CH2) were synthesized. Their thermal properties and water miscibility were investigated and compared with those of the corresponding Tf2N (= (SO2CF3)2N–) salts. Exposure of these ILs to bromine vapor produced bromine adducts, tribromide salts, and a small amount of a cyclic adduct derived from the anion. The reaction products and the potassium salt of the anion were characterized crystallographically.

Thermal Elimination of Ethylene from Cyclobutyl Groups Characterized by X-ray Crystallography in a Metal-Organic Framework Matrix.

Methods to synthesize and characterize aromatic molecules with vinyl substituents are sought after yet limited in the literature. Here, we introduce cyclobutyl groups into a metal-organic framework (MOF) matrix that are poised to produce ethylene upon heating. The expulsion of ethylene produces vinyl groups on an aromatic core, which are isolated by the crystalline matrix of the framework. This enables full characterization of the thermolysis by single-crystal X-ray diffraction. Further, we modify the vinyl groups by a bromine addition reaction. Importantly, the two transformations happen in a single-crystal-to-single-crystal manner without changing the overall network structure of the parent framework. New insights into the structural and synthetic chemistry of this important class of compound are generated. Installing reactive vinyl tags in materials by the high temperature thermolysis of cyclobutyl groups is a powerful strategy for altering their physicochemical characteristics.

An aliphatic hexene-covalent triazine framework for selective acetylene/methane and ethylene/methane separation

Aliphatic hexene-covalent triazine framework for C2/C1 hydrocarbon separation – dependence on morphology.

Synthesis of membrane adsorbers via surface initiated ATRP of 2-dimethylaminoethyl methacrylate from microporous PVDF membranes

Surface-initiated atom transfer radical polymerization (SI-ATRP) was used to tether poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) onto microporous PVDF membranes in order to synthesize membrane adsorbers for protein adsorption. The alkaline treatment and bromine addition reaction were used to anchor ATRP initiators on membrane surface. Then PDMAEMA was grafted from the membrane surface via SI-ATRP. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) revealed the chemical composition and surface topography of the PVDF-g-PDMAEMA membrane surfaces. These results showed that PDMAEMA was grafted from the membrane surface successfully and a grafting yield as high as 1500 μg/cm2 was achieved. The effects of the grafting time and the density of initiators on the static and dynamic binding capacity of bovine serum albumin (BSA) were systematically investigated. Both the static and dynamic binding capacities increase with the bromination and polymerization time. However, the benefits of the initiator density on binding capacities are limited by the graft density of PDMAEMA chains.

Preparation and Strongly Enhanced Visible Light Photocatalytic Activity of TiO2 Nanoparticles Modified by Conjugated Derivatives of Polyisoprene

Conjugated polymer modification is one of the most promising methods for preparing TiO2-based visible-light-responsive photocatalysts. In this article, TiO2 nanoparticles modified by conjugated derivatives of polyisoprene (CDPIP) were prepared from TiO2/polyisoprene nanocomposites by the bromine addition reaction of polyisoprene and dehydrobromination reaction of the brominated polyisoprene. The visible light photocatalytic activities of as-prepared nanocomposites were evaluated using methyl orange as the model contaminant and two indoor fluorescent lamps with a 400 nm cutoff filter as the visible light source. TEM images show that a layer of CDPIP attaches on the surface of TiO2 nanoparticles. XPS, FTIR, and Raman spectra further reveal the conjugated structure of CDPIP. The results of XRD, UV–vis DRS, and PL spectra show that modification of CDPIP does not change the crystalline structure of TiO2, greatly improves the absorbance of the nanocomposites in the whole range of visible light, and obviously re...

DFT and MP2 study on the electrophilic addition reaction of bromine to exo-tricyclo[3.2.1.02.4]oct-6-ene

The geometry and electronic structure of exo-tricyclo[3.2.1.0(2,4)]oct-6-ene (exo-TCO) was investigated using DFT methods. The two faces of the endo-pyramidalised double bond of the molecule are not equivalent. The exo face of the double bond has regions with high electron density (q (i,HOMO)) and greater negative potential. Molecular complexes of exo-TCO with bromine were investigated using the B3LYP/6-311++G(d,p) method; the exo-TCO . . . Br(2)(exo) molecular complex was found to be relatively more stable than the exo-TCO . . . Br(2)(endo) complex. The cationic intermediates of the reaction were studied by DFT and MP2 methods. The solvent effect was evaluated using the self-consistent isodensity polarised continuum model (SCI-PCM). The exo-bromonium cation was found to be more stable than the endo-bromonium cation. Exo-facial selectivity due to electronic and steric factors was observed upon addition of bromine to exo-TCO. The multicentre nonclassical delocalised bromocarbonium cation IV and the exo-bridged-bromonium cation I are more stable than the rearrangement cation V. The reaction products are formed via exo-bridged-bromonium I and nonclassical IV cations, which are the most stable intermediates and whose stabilities barely differ. The mechanism of the addition reaction is also discussed.

Density functional theory investigation of electrophilic addition reaction of bromine to tricyclo[4.2.2.22,5]dodeca-1,5-diene1

The geometry and the electronic structure of tricyclo[4.2.2.2(2,5)]dodeca-1,5-diene (TCDD) molecule were investigated by DFT/B3LYP and /B3PW91 methods using the 6-311G(d,p) and 6-311++G(d,p) basis sets. The double bonds of TCDD molecule are syn-pyramidalized. The structure of pi-orbitals and their mutual interactions for TCDD molecule were investigated. Potential energy surface (PES) of the TCDD-Br(2) system was studied by B3LYP/6-311++G(d,p) method and the configurations [molecular charge-transfer (CT) complex, transition states (TS1 and TS2), intermediate (INT) and product (P)] corresponding to the stationary points (minima or saddle points) were determined. Initially, a molecular CT-complex forms between Br(2) and TCDD. With a barrier of 22.336 kcal mol(-1) the CT-complex can be activated to an intermediate (INT) with energy 15.154 kcal mol(-1) higher than that of the CT-complex. The intermediate (INT) then transforms easily (barrier 5.442 kcal mol(-1)) into the final, N-type product. The total bromination is slightly exothermic. Accompanying the breaking of Br-Br bond, C1-Br, C5-Br and C2-C6 bonds are formed, and C1 = C2 and C5 = C6 double bonds transform into single bonds. The direction of the reaction is determined by the direction of intramolecular skeletal rearrangement that is realized by the formation of C2-C6 bond.

Ab initio and DFT study of the inner mechanism and dynamic stereochemistry of electrophilic addition reaction of bromine to bisbenzotetracyclo[6.2.2.23,6.02,7]tetradeca-4,9,11,13-tetraene

The inner mechanism and dynamic stereochemistry of electrophilic addition of bromine to bisbenzotetracyclo[6.2.2.2(3,6).0(2,7)]tetradeca-4,9,11,13-tetraene(BBTT) molecule have been investigated by the methods of quantum chemistry. The structure of the BBTT molecule has been studied by ab initio and DFT/B3LYP methods using the 6-31G(d) and 6-311G(d) basis sets. The double bonds of BBTT molecule are endo-pyramidalized. The structure and stability of the cationic intermediates and products of the addition reaction have been investigated by HF/6-311G(d), HF/6-311G(d,p), B3LYP/6-311G(d) and B3LYP/6-311++G(2d,p)//B3LYP/6-311G(d) methods. The bridged bromonium cation isomerized into the more stable nonclassical delocalized N- and U-type cations and the difference between the stability of these cations is small. For the determination of the direction of addition reaction and the stereochemistry of the products, the stability of nonclassical delocalized N- and U-type ions and the structure of their cationic centres play a vital role. Since the cationic centre of the N-type ion is in interaction with the benzene ring from the exo face, the nucleofilic attackof the bromide anion to this centre occurs from the endo face and the exo,endo-isomer of the N-type product is obtained. The attack of bromide anion, towards the cationic centre of U-type ion from the endo face is sterically hindered by the hydrogen atom therefore the attack occurs from the exo face, which interacts with the benzene ring and the more stable exo,exo-isomer of U-type product is formed. Although, the U-type cation was 2.232 kcal mol(-1) more stable than the N-type cation, the U-type product was 0.587 kcal mol(-1) less stable than the N-type product.

Ab initio and DFT investigation of electrophilic addition reaction of bromine to endo,endo-tetracyclo[4.2.1.13,6.02,7]dodeca-4,9-diene

Full geometric optimization of endo,endo-tetracyclo[4.2.1.1(3,6).0(2,7)]dodeca-4,9-diene (TTDD) has been carried out by ab initio and DFT/B3LYP methods and the structure of the molecule investigated. The double bonds of TTDD molecule are endo pyramidalized. The structure of pi-orbitals and their mutual interactions for TTDD molecule were investigated. The cationic intermediates and products obtained as a result of the addition reaction have been studied using the HF/6-311G(d), HF/6-311G(d,p) and B3LYP/6-311G(d) methods. The bridged bromonium cation isomerized into the more stable N- and U-type cations and the difference between the stability of these cations is small. The N- and U-type reaction products are obtained as a result of the reaction, which takes place via the cations in question. The stability of exo, exo and exo, endo isomers of N-type product are nearly the same and the formation of both isomers is feasible. The U-type product basically formed from the exo, exo-isomer. Although the U-type cation was 0.68 kcal mol(-1) more stable than the N-type cation, the U-type product was 4.79 kcal mol(-1) less stable than the N-type product.

Allyl functionalized telechelic linear polymer and star polymer via RAFT polymerization

Reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene using bisallyl trithiocarbonate as a chain transfer agent (CTA) was studied. The polymerization exhibited first-order kinetics and the molecular weight increased linearly with increase of monomer conversion. Well defined allyl-functionalized telechelic polystyrene (PS), poly(tert-butyl acrylate) (PtBA) and corresponding triblock copolymers, polystyrene-b-poly(n-butyl acrylate)-b-polystyrene (PS-b-PnBA-b-PS) and poly(tert-butyl acrylate)-b-polystyrene-b-poly(tert-butyl acrylate) (PtBA-b-PS-b-PtBA) were prepared as characterized with GPC and NMR analysis. The allyl-end groups of the telechelic PS have been switched to 1,2-dibromopropyl groups quantitatively by bromine addition reaction, further substitution of the bromide with azide was also made. Furthermore, star PS with allyl-end-functionalized arms was synthesized by RAFT polymerization of divinyl benzene using allyl-functionalized PS as a macro-CTA via arm-first approach. Star polymer with a thiol-functionalized core was generated by aminolysis reaction of the star polymer and ethylenediamine. As a result, difunctionalized star polymer with allyl and thiol groups was obtained and was used as a stabilizer for the formation of gold nanoparticles.

Ab initio and DFT study on the electrophilic addition reaction of bromine to tetracyclo[5.3.0.02,6.03,10]deca–4,8–diene

The electronic and geometric structures of tetracyclo[5.3.0.0(2,6).0(3,10)]deca-4,8-diene (hypostrophene) have been investigated by ab initio and DFT/B3LYP methods using the 6-31G* and 6-311G* basis sets. The double bonds of hypostrophene are endo-pyramidalized. The cationic intermediates and products formed in the addition reaction have been investigated using the HF/6-311G*, HF/6-311G**, and B3LYP/6-311G* methods. The bridged bromonium cation was more stable than the U-type cation. Considering that the bridged cation does not isomerize to the less stable U-type cation, it is not possible for the U-type product to be obtained in the reaction. The bridged bromonium cation transformed into the more stable N-type cation and the N-type product was obtained via this cation. The thermodynamic stability of the exo, exo and exo, endo isomers of the N-type dibromide molecule were almost identical. The N-type product was 16.6 kcal mol(-1) more stable than the U-type product.

Electrophilic Anti Addition of Bromine to 2-Methylbut-2-ene with the N-Methylpyrrolidin-2-one Hydrotribromide Complex

Despite the fact that bromine is very toxic by inhalation, highly corrosive, and may cause serious burns, its electrophilic addition reaction continued to be featured in the second-year laboratory course at Paris XI University. It had customarily been performed by the addition of a solution of bromine in chloroform to olefinic compounds such as 2methylbut-2-ene (1). The laboratory exercise also required two liquid purification techniques: liquid‐liquid extraction followed by two kinds of distillation. Furthermore, preparation of the chloroform solution of bromine (8%) required manipulation of large quantities of bromine, and even the use of the resulting solution could not prevent bromine fumes. Moreover, the addition reaction of bromine to 2methylbut-2-ene is an exothermic process, inducing evaporation of olefinic compound and therefore decreasing the overall reaction yield. For safety considerations, we proposed that bromine no longer be used and be replaced in the student laboratory by another brominating agent. In our university, molecular bromine has been substituted by the N-methylpyrrolidin-2-one hydrotribromide complex (MPHT; ref 2 ) whose crystalline data have been recently published (3). This orange crystalline complex has been prepared by an experienced chemist in large quantities, following a slightly modified version of Daniels’ procedure (ref 2; Scheme I). The MPHT complex is a stable solid that can be stored several months at room temperature; after a six-month storage test at room temperature no decrease in the free bromine titer could be detected. MPHT is not corrosive, not necrosing, less toxic, and easier to handle for students than molecular bromine. This complex smoothly liberates bromine in organic solvents according to Scheme II. The addition reaction was performed at room temperature in dichloromethane using 2-methylbut-2-ene. Discoloration of the resulting orange solution could be observed by students as long as MPHT is consumed. N-Methylpyrrolidin-2-one hydrobromide and N-methylpyrrolidin-2-one are byproducts of the reaction and are removed by washing the organic layer with water. Over a one-year period, the majority of the 230 students successfully completed this experiment with overall yields ranging from 35 to 80%.

Kinetics of the Conformer Reactions: II. Significance of Media in the Electrophilic addition Reactions

The kinetics of electrophilic addition reaction of bromine to a multiple bond in a series of con-formationally unhomogenous 2-substituted 1'3-dioxa-5-cycloheptenes was studied. We found that the com-pounds with trans structure are formed. The partial reaction rate constant for chair, twist forms, thereaction susceptibility parameters to the substituent electronic effect at the C2atom are obtained. Relativereactivity of the alternative steric structures is defined by the specific solvation of the substrate. The result obtained are compared with those achieved without accounting for conformational term.

A quantum chemical investigation of electrophilic addition reaction of bromine to benzonorbornadiene

The molecular complexes formed by the treatment of bromine with benzonorbornodiene have been studied by the AM1 semiempirical method and their stable configurations and also stabilization energies have been determined. It has been found that the molecular complexes formed by the attack of bromine on the double bond of benzonorbornadiene, from the exo direction are more stable than those formed from the endo direction. Possible various cations and radical intermediates of the electrophilic addition reaction of bromine to benzonobornadiene have been investigated by MNDO and ab initio methods. The nonclassical delocalized bromocarbonium cation is the most stable among these cations according to both methods, and the ionic addition reaction occurs via this cation.

(E)-o-Stilbenecarboxylic Acid and itsp-Methyl, Chloro and Methoxy Derivatives

The crystal structures of the title compounds, (E)-stilbene-1-carboxylic acid, C15H12O2, (Ia), (E)-4′-methylstilbene-1-carboxylic acid, C16H14O2, (Ib), (E)-4′-chlorostilbene-1-carboxylic acid, C15H11ClO2, (Ic) and (Ic'), and (E)-4′-methoxystilbene-1-carboxylic acid, C16H14O3, (Id), have been determined. The chloro derivative shows polymorphism, with prisms, (Ic), being obtained from ether/hexane solution and needle crystals, (Ic'), being obtained from ethanol solution. The latter is isostructural with (Id). The selectivities of the products to the addition reaction of bromine are different, however, suggesting that the bromonium ion intermediate is stabilized by a resonance contribution of the p-MeO group.

ChemInform Abstract: The β‐Effect: Changing the Ligands on Silicon.

AbstractThe addition reaction of bromine to the β‐silylstyrenes (I) is monitored by NMR analysis.

Bromine Addition Reaction to Olefins with Magnesium Bromide and Aroyl Peroxides

Abstract When MgBr2 prepared in anhydrous tetrahydrofuran was added to a mixture of olefin and benzoyl peroxide, the peroxide decomposed at a moderate rate at room temperature. Olefin dibromide and magnesium benzoate were obtained in nearly quantitative yields. The effects of p- and m-substituents of peroxide and of the structure of olefin were studied. A complex consisting of MgBr2 and peroxide was formed. Abstraction of brominium cation from the complex by the olefinic double bond was proposed.

Synthesis of nitrofuran derivatives. X. Synthesis of 2-(4-bromo-3-oxo-1-butenyl)-5-nitrofuran and its derivatives

Both 2-(4-bromo-3-oxo-1-butenyl)-5-nitrofuran (III) and 2-(4, 4-dibromo-3-oxo-1-butenyl)- 5-nitrofuran (IV) were synthesized by bromination of 2-(3-oxo-1-butenyl)-5-nitrofuran (II) in acetic acid or chloroform, blowing off the formed hydrogen bromide by nitrogen gas stream. To avoid the formation of IV, diethyl 3-(5-nitro-2-furyl)acryloylmalonate (I) was brominated under the same conditions as described above, followed by acid catalyzed hydrolysis, and III was obtained with a small amount of its isomer, 2-(2-bromo-3-oxo-1-butenyl)-5 nitrofuran (VI). In these cases, the addition reaction of bromine or hydrogen bromide to the double bond was not observed. III was reacted with hydrochloric acid and acetic acid in the pre-sence of guanidine carbonate to give 2-(4-chloro-3-oxo-1-butenyl)-5-nitrofuran (X) and 2-(4-acetyloxy-3-oXo-1-butenyl)-5-nitrofuran (XI) respectively. Their antimicrobial activities were presented.

The Oxygen Effect in the Hydrogen Bromide Catalysis of the Addition Reaction of Bromine to Cinnamic Acid in Carbon Tetrachloride Solution

Abstract It has been found that a joint action of hydrogen bromide and oxygen accelerates the addition of bromine to cinnamic acid in carbon tetrachloride solution in the dark, whereas the reaction is retarded by either of them. The catalyzed reaction is prevented by catechol, and hydrogen chloride cannot be substituted for hydrogen bromide without the dis？ppearance of the accelerating effect. On the basis of these observations the nature of the alleged catalysis of the addition of bromine by hydrogen bromide has been elucidated. The elimination of the induction period, which is certainly attributable to the inhibitory action of oxygen, is not due to the removal of the latter. The explanation offered is that hydrogen bromide and an ethenoid compound in co-operation with the very oxygen starts a rapid chain reaction involving bromine atoms and free radicals. Also for the uncatalyzed addition of bromine to cinnamic acid in carbon tetrachloride a possibility of a mechanism involving chains has been suggested.

A Study of the Phenanthrene—Bromine Addition Reaction

A Study of the Phenanthrene—Bromine Addition Reaction