Bromination of poly[1-(trimethylsilyl)-1-propyne] with different microstructures and properties of bromine-containing polymers

The interaction between poly[1-(trimethylsilyl)-1-propyne] with different microstructures and bromine has been studied in carbon tetrachloride and chlorobenzene at 25–120°C. Depending on the process conditions, polymers containing up to 26 wt % bromine are formed; that is, every other unit of the polymer chain is brominated. Polymers enriched with cis structures are brominated through trimethylsilyl groups, and the process is unaccompanied by polymer chain degradation. The bromination of samples containing predominantly trans-structures is nonselective, and the reaction is accompanied by polymer degradation. The solubility of brominated poly[1-(trimethylsilyl)-1-propyne] in different media and the gas permeability of films made of this polymer are estimated.     

Characterisation of five technical mixtures of brominated flame retardants

The main components of five technical mixtures of brominated flame retardants were identified by mass spectroscopy, H-NMR, IR spectroscopy, elementary analysis, and HRGC-MS, respectively. The mixtures have been identified as: phosphoric acid bromopropylates: Bromcal P 67-6 HP; C18-alkylated bromophenols: Bromcal P 40-3; dibromopropyl-2,4,6-tribromophenyl ether: Bromcal 73-5 PE; brominated diphenyl ethers (PBrDE): Bromcal 70-5 DE; decabromodiphenyl ether: Bromcal 82-0. Gas chromatographic retention data of the various constituents were measured on standard GC columns. The data prove the interference of some of the brominated compounds with PCBs and other halogenated pesticides in HRGC using the electron capture detector.     

A New Brominated Phenylpropylaldehyde and its Dimethyl Acetal from Red Alga Rhodomela confervoides

A new brominated phenylpropylaldehyde and its dimethyl acetal together with a new natural brominated phenol were isolated from Rhodomela confervoides. Their structrues were elucidated as 2-methyl-3-(2,3-dibromo-4,5-dihydroxyphenyl)propylaldehyde, 2-methyl-3-(2,3-di-bromo-4,5-dihydroxyphenyl) propylaldehyde dimethyl acetal and 3-bromo-4,5-dihydroxybenzoic acid methyl ester by spectroscopic techniques including IR, HRFABMS, 1D and 2DNMR experiments.     

Synthesis of 2-Functionalized 4-(Diethoxyphosphorylmethyl)-5-(1-bromoalkyl)furans and Their Reactions with Amines

Phosphorylation of esters and nitriles of 4-chloromethyl-5-alkylfuran-2-carboxylic acids with triethyl phosphite yields the corresponding phosphonates. These compounds are brominated with N-bromosuccinimide in carbon tetrachloride at the α-position of the alkyl radical. The resulting 2-(1-bromoethyl)-, 2-(1-bromopropyl)-, and 2-(1-bromoisobutyl)furans react with secondary amines following the scheme of nucleophilic substitution. The dehydrobromination product was isolated only in the reaction of ethyl 4-(diethoxyphosphorylmethyl)-5-(1-bromoisopropyl)furan-2-carboxylate with triethylamine, but its yield was low. The reactions of bromo phosphonates with lithium carbonate in DMF result in their decomposition.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 5, 2005, pp. 820–828.Original Russian Text Copyright © 2005 by Pevzner.     

Location and base selectivity on fragmentation of brominated oligodeoxynucleotides

Bromine-modified oligodeoxynucleotides (ODNs) were fragmented in the electrospray source to study the influence of brominated bases on fragmentation. Several 13-mer ODNs containing a brominated pyrimidine base, BrdU (5-bromodeoxyuridine) or BrdC (5-bromodeoxycytidine), were analyzed. Low cone voltage fragmentation yields a loss of the brominated base with a preferential loss for the brominated base closer to the 5'-end (2-position > 4-position > 12-position) as well as a preferential loss of BrdU over BrdC. Higher cone voltage produces backbone fragmentation with complementary a(n)-base and w(m) ions close to the brominated base. On the basis of these observations, we located the brominated base in the sequence for all of the ODNs studied.     

Hydroxyl-radical-initiated oxidation mechanism of bromopropane

Bromopropane has been considered as a replacement for chlorofluorocarbons used as the active component of industrial cleaning solvents, more specifically for HCFC-141b. The proposed mechanism for the atmospheric oxidation of bromopropane is studied via ab initio methodology. Ab initio molecular orbital methods at the CCSD(T)/6-311++G(2df,2p)//MP2/6-31G(d) level of theory have been used to determine the structure and energetics of the 58 species and transition states involved in the atmospheric oxidation of bromopropane. The calculations show that the major oxidation species is bromoacetone. Other brominated species that result from the oxidation are BrCH 2CH 2C(O)H, BrC(O)CH 2CH 3, and BrC(O)H, potential new bromine reservoir species that result from bromopropane in the atmosphere.     

Differential substituent effects of beta-halogens in water-soluble porphyrins

The first water-soluble beta-octafluorinated porphyrins, 5,10,15,20-tetrakis(4-sulfonatophenyl)-2,3,7,8,12,13,17,18- octafluoroporphyrin, 1, and 5,10,15,20-tetrakis(2,6-difluoro-3-sulfonatophenyl)-2,3,7,8,12,13,17,18- octafluoroporphyrin, 2, have been prepared and their aqueous aggregation, acid-base, and optical properties have been characterized. The porphyrins are tetraanionic at neutral pH (at pH = 3-11 for 1 and pH = 0-9 for 2). Semiempirical (AM1) calculations provide evidence that somewhat unusual acidity characteristics of the fluorinated compounds (with respect to similar brominated porphyrins) can be rationalized solely on the basis of chemical hardness and electronegativity arguments. These results indicate that the large conformational differences seen in the structures of brominated and fluorinated water-soluble porphyrins have little impact upon N-H acidity. Metalation of 1 and 2 with ZnCl2 yielded the zinc complexes, which were characterized by optical spectroscopy and electrochemistry.     

Controlled pyrolysis of polyethylene/polypropylene/polystyrene mixed plastics with high impact polystyrene containing flame retardant: Effect of decabromo diphenylethane (DDE)

The pyrolysis of polyethylene(PE)/polypropylene(PP)/polystyrene(PS) mixed with high impact polystyrene (HIPS-Br) containing decabromo diphenylethane (DDE) as a brominated flame retardant with antimony trioxide as a synergist was performed under controlled temperature programmed pyrolysis (two steps) conditions to understand the decomposition behaviour and evolution of brominated hydrocarbons from flame-retardant additives. The liquid products were extensively analyzed by gas chromatographs equipped with FID, ECD, MSD, TCD, AED and FT-IR. The solid residue samples were analyzed by powder X-ray diffraction and combustion followed by ion-chromatography. The controlled pyrolysis of PE/PP/PS/HIPS-Br significantly affected the decomposition behaviour of HIPS-Br and subsequently the formation of decomposition products. GC/ECD analysis confirmed that the brominated hydrocarbons were concentrated in step 1 liquid products leaving less brominated hydrocarbons in the step 2 liquid products, similar to the decabromo diphenyl ether flame retardant containing mixed plastics. The yield of liquid products in step 1 from 3P/DDE-Sb(5) was 5 wt% and from 3P/DDE-Sb(0) was 2.4 wt%. The presence of antimony in the DDE containing plastics affected the yield of liquid, gas and residue products. ECD analysis showed that the presence of antimony increased the Br containing hydrocarbons and step 1 has 3-4 times higher brominated compounds than step 2 hydrocarbons in both the samples.     

Bromine-induced cyclization of 1-acyl-3-(3-thienyl)-2-thioureas to 2-acylaminothieno[3,2-d]thiazoles

Three different 1-acyl-3-(3-thienyl)-2-thioureas were cyclized to 2-acylaminothieno[3,2-d]thiazoles with bromine in acetic acid whereas the corresponding 2-thienylthiourea derivatives were brominated under the same reaction conditions. The parent thieno[3,2-d]thiazole was prepared by acid hydrolysis and deamination of 2-benzoylaminothieno[3,2-d]thiazole. This new heterocyclic compound was nitrated and brominated in the 5-position.     

Polybutadiene Modification: Reactions of Halogen-Containing Polybutadienes with Organolithium Compounds

Polybutadiene (PB) can be easily halogenated by reaction with iodine chloride or bromine in tetrahydrofuran. The resulting glassy polymers were reacted with n-butyllithium, sec-butyl-lithium, and polystyryllithium in THF. Iodochlorinated PB gave a polybutadiene with a different cis/trans ratio with n-BuLi. The reformation of PB was accompanied by partial crosslinking. The reaction probably involved a halogen-metal exchange followed by intra- and intermolecular elimination of Li halide. With brominated PB, both coupling and elimination took place. With sec-BuLi, an allylic iodine derivative was obtained from iodochlorinated PB, probably by dehydrochlorination. The iodinated intermediate can easily undergo a coupling reaction with further sec-BuLi. Both iodochlorinated and brominated polybutadienes gave graft copolymers by reaction with polystyryllithium in THF. Grafting was always accompanied by gel formation.     

Nonselective bromination-selective debromination strategy: selective bromination of unsymmetrical ketones on singly activated carbon against doubly activated carbon

[reaction: see text] We have found a new synthetic method for the preparation of the alpha-bromoketones that are brominated in the less activated terminal position of unsymmetrical ketones. Brominations in short reaction times (kinetically controlled) provided internally brominated compounds as a major product. However, brominations in longer reaction times (thermodynamically controlled) gave more of the terminally brominated compound through the reversible reaction by Br(2) and produced hydrogen bromide. Several brominated compounds at the terminal position were successfully prepared through the new synthetic route.     

Pressurised hot water extraction coupled on-line with liquid chromatography-gas chromatography for the determination of brominated flame retardants in sediment samples

Pressurised hot water extraction (PHWE) was coupled on-line with liquid chromatography-gas chromatography (LC-GC) to determine brominated flame retardants in sediment samples. After extraction with pressurised hot water the analytes were adsorbed in a solid-phase trap. The trap was dried with nitrogen and the analytes were eluted to the LC column, where the extract was cleaned, concentrated and fractionated before transfer to the GC system. The fraction containing the brominated flame retardants was transferred to the GC system via an on-column interface. The PHWE-LC-GC method was linear from 0.0125 to 2.5 microg with limits of detection in the range 0.70-1.41 ng/g and limits of quantification 6.16-12.33 ng/g.     

Effect of the reaction medium on the bromocyclization of maleic and fumaric acid monoureides

The monopotassium salt of maleic acid monoureide is brominated in water in the same way as the free acid, whereas the trans isomer is not brominated at all. Bromocyclization of the monopotassium salt of the cis isomer to give 5-(bromocarboxy-methyl)hydantoin and intramolecular cyclization to give 5-(carboxymethyl)hydantoin are realized at pH 4–6. erythro-2,3-Dibromosuccinic acid and 5-(bromo-carboxy-methyl)hydantoin are formed in the bromination of the monopotassium salt of fumaric acid monoureide at pH 4–6. Bromination of the methyl ester of maleic acid monoureide in 1,2-dichloroethane proceeds in the same way as bromination in water to give 2-amino-5-[bromo(methoxycarbonyl)methyl]oxazolid-4-one.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1474–1481, November, 1980.     

Smoke suppression of graphene platelets fabricated by Friedel–Crafts reaction in brominated flame-retarded PS

Journal of Thermal Analysis and Calorimetry - Graphene nanoplatelets (GNPs) were introduced into polystyrene (PS)/brominated polystyrene (BPS) blends to suppress the large amounts of smoke...     

Brominaed β-carbolines from the marine hydroid linnaeus

Three new brotminated β-carbolines (1–3) have been isolated from the lipophylic extract of the marine hydroid Linnaeus and their structures determined on the basis of spectral data including two dimensional proton-carbon shift correlation (direct and long range) NMR spectroscopy. The syntheses of compounds 1–3, starting from the appropriate brominated tryptophan derivatives, are also described.     

溴代及胺交联聚苯醚（PPO）膜的气体透过行为

对聚苯醚(PPO)进行了苯环溴代、甲基溴代以及胺交联,发现苯环溴代可提高O_2、N_2透过率(P),而选择性(α)基本不变。甲基溴代则相反,P降低、α有明显提高。调节两者比例可得到P、α兼优的O_2、N_2分离膜。甲基溴代后进一步胺交联可得到α更高、耐溶剂的膜材料。     

Studies directed toward total synthesis of rhodocomatulins: A regioselective synthesis of brominated hydroxyanthraquinones by anionic annulations

In this work, brominated hydroxyanthraquinones, which are the core structural motif of naturally occurring bromorhodocomatulins, were successfully synthesized using Hauser annulation reaction as the key step. When brominated Michael acceptors (brominated p-quinone monoketals) and cyanophthalides or bromocyanophthalides (Hauser donors) were reacted under the annulation conditions, brominated anthraquinones were obtained with 81–87% yields for four examples. On acidic quenching, products were obtained as solid which were separated by filtration and purified by recrystallization in acetone. No chromatography was required.     

New fire retardant halogenfree polymers

Todays fire retardant plastics for high strength FRP (fibre-reinforced polymers) or electronic devices (printed circuit boards, PCB) are based on brominated epoxy resins (EP resins). The smoke gases of this resins are highly toxic and corrosive. A new class of fire retardant duroplastics, based on dihydrobenzoxazines, doesn't contain halogen, sulfur or phosphor. Processibility is equal to that of thermosetting epoxy resins. Mechanical and electrical properties are equal to brominated epoxy resin, heat resistance is considerably enhanced (glass temperature 180 - 280 °C), while density, toxicity and corrosivity of smoke are very low.     

Reaction of 2,4-Difunctional Esters of 5-tert-Butylfuran-3-carboxylic Acid with Nucleophilic Reagents

Ethyl 5-tert-butyl-4-(chloromethyl)-2-methylfuran-3-carboxylate was brominated with N-bromo-succinimide to obtain the corresponding 2-bromomethyl derivative. The latter is selectively phosphorylatedwith trimethyl, triethyl phosphites by the bromomethyl group. The resulting [4-(chloromethyl)furyl]methyl-phosphonates in the presence of secondary amines and sodium butanethiolate behave as alkylating agents,while sodium phenolate causes their decomposition. 4-Acetoxymethyl- and 4-phenoxymethyl derivatives of the starting product are also selectively brominated with N-bromosuccinimide by the 2-methyl group. The first of the 2-(bromomethyl)furans formed is smoothly phosphorylated with trimethyl phosphite, while the second one under the action of triethyl phosphite gives a mixture of phosphorylation and debromination products. In all the cases, an additional electron-acceptor group in position 4 of alkyl 2-(bromomethyl)-5-tert-butylfuran-3-carboxylate considerably accelerates the Arbuzov reaction.     

Sequential Pd(II)-Pd(0) catalysis for the rapid synthesis of coumarins

Electrophilic palladium-catalyzed cycloisomerization of brominated aryl propiolates produces brominated coumarins. The brominated coumarins can be diversified by reduction of the Pd(II) catalyst to Pd(0) followed by Suzuki, Sonogashira, Heck, or Hartwig-Buchwald coupling. Thus, a single loading of precatalyst can be used to conduct sequential reactions, allowing the synthesis of functionalized coumarins. Extension of this methodology toward the synthesis of coumarin libraries is discussed.