- Instantaneous, facile and selective synthesis of tetrabromobisphenol a using potassium tribromide: An efficient and renewable brominating agent
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An instantaneous method for the bromination of bisphenol A has been reported using potassium tribromide for the first time as an efficient brominating agent affording the corresponding tetrabromobisphenol A in a reaction time of only 5 - 10 min at ambient temperature in high yields (99%) and purity (>99%), free from reaction byproduct and having very low ionic impurities. Mild reaction conditions and simple workup provide a practical and commercially viable route for the synthesis of the largest selling flame retardant. The generated HBr during the bromination reaction is used either in the preparation of value-added brominated products or is disposed of as waste, causing serious environmental problems. An environmentally acceptable method for an inbuilt recycling of HBr by its neutralisation, thereby generating additional amounts of metal bromide and recovering the solvent from the liquid mixture has been designed and developed. The KBr used for the preparation of potassium tribromide can be recovered, regenerated in additional amounts, and reused without any significant loss.
- Kumar, Lalit,Sharma, Vivek,Mahajan, Tanu,Agarwal
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Read Online
- Electrophilic bromination in flow: A safe and sustainable alternative to the use of molecular bromine in batch
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Bromination reactions are crucial in today’s chemical industry since the versatility of the formed organobromides makes them suitable building blocks for numerous syntheses. However, the use of the toxic and highly reactive molecular bromine (Br2) makes these brominations very challenging and hazardous. We describe here a safe and straightforward protocol for bromination in continuous flow. The hazardous Br2 or KOBr is generated in situ by reacting an oxidant (NaOCl) with HBr or KBr, respectively, which is directly coupled to the bromination reaction and a quench of residual bromine. This protocol was demonstrated by polybrominating both alkenes and aromatic substrates in a wide variety of solvents, with yields ranging from 78% to 99%. The protocol can easily be adapted for the bromination of other substrates in an academic and industrial environment.
- Van Kerrebroeck, Reinout,Naert, Pieter,Heugebaert, Thomas S.A.,D’hooghe, Matthias,Stevens, Christian V.
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- Electrochemical synthesis of quinones and other derivatives in biphasic medium
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Electrochemical synthesis of quinones has been attempted from phenols, 1,4-dihydroxybenzenes, 1,4-dihydroxynaphthalenes and related compounds using biphasic media. Excellent yields of quinones (98%) or brominated diols have been achieved with good current efficiency. Reuse of the electrolyte without any modification and quantitative conversion of substrate with theoretical amount of current are the advantages of this method.
- Shanmugam,Kulangiappar,Ramaprakash,Vasudevan,Senthil Kumar,Velayutham,Raju
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p. 2294 - 2297
(2017/05/19)
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- Hexamethonium bis(tribromide) (HMBTB) a recyclable and high bromine containing reagent
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A recyclable and high bromine containing di-(tribromide) reagent, hexamethonium bis(tribromide) (HMBTB) has been synthesized and utilized for the bromination of various organic substrates. The spent reagent hexamethonium bromide (HMB) can be effectively recycled by regenerating and reusing it without significant loss of activity. The crystalline and stable bis(tribromide) is an effective storehouse of very high percentage of active bromine requiring just half an equivalent of it for complete bromination. Both the Br3- moieties in HMBTB are nearly linear with Br-Br-Br angle of 179.55°.
- Paul, Bappi,Bhuyan, Bishal,Purkayastha, Debraj D.,Dhar, Siddhartha S.,Patel, Bhisma K.
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p. 5646 - 5650
(2015/09/21)
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- Supramolecular organic frameworks of brominated bisphenol derivatives with organoamines
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Reactions of two brominated bisphenol derivatives, tetrabromobisphenol-F (TBBPF) and tetrabromobisphenol-A (TBBPA), with various organoamines resulted in six supramolecular organic frameworks (SOFs), formulated as (TBBPF 2-)2·(HPZ+)2· (H 2PZ2+) (1), (TBBPF-)2· (H2PZ2+)·2H2O·2MeOH (2), (TBBPF) · (TBBPF-)· (HDABCO+)·H2O (3), (TBBPF) · (HMTA) (4), (TBBPA) · (HMTA) (5), and (TBBPA) 3· (HMTA)3·H2O (6) (PZ = piperazine; DABCO = diazabicyclo[2.2.2]octane; HMTA = hexamethylenetetramine). Compounds 1-6 were characterized by single-crystal and powder X-ray diffractions. The predominant driving forces in 1-6 are hydrogen bonds (H-bonds), by which the compounds assemble into supramolecular organic frameworks with versatile topological structures. Compound 1 contains TBBPF/PZ in a 2:3 ratio and exhibits 2D (two-dimensional) H-bonded supramolecular 4 4-sql layer structure built by the four-connected {H 2PZ2+} moieties and {TBBPF2-}. Compound 2 shows a 2-fold interpenetrated 3D (three-dimensional) H-bonded networks comprised by TBBPF/PZ in 2:1 ratio with the presence of solvent H2O and MeOH molecules, in which two identical pcu topological nets are recognized by choosing a decamer synthons as nodes. Compound 3 displays H-bonded 4 4-sql layer structure built by 2:1 TBBPF and DABCO, as well as one H2O per formula unit. Compounds 4 and 5 assemble into 1D (one-dimensional) H-bonded zigzag chains via the alternate linkage of HMTA with TBBPF/TBBPA in a similar fashion. Compound 6 generates an interesting hexamer subunit (HMTA ...TBBPA ...HMTA ...TBBPA ...HMTA...TBBPA), which can be viewed as a fragment of three repeating units for a zigzag chain observed in compound 5. A pair of the hexamer subunits is further connected by two water molecules to form an H-bonded molecular oligomer. Importantly, halogen bonds (X-bonds) have been observed in compounds 4-6 that exhibit 1D and 0D H-bonded supramolecular structures.
- Lue, Jian,Han, Li-Wei,Lin, Jing-Xiang,Cao, Rong
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experimental part
p. 3551 - 3557
(2012/03/27)
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- Process for the Preparation of Tetrabromobisphenol A
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A process for preparing tetrabromobisphenol A, which comprises: i) reacting bisphenol A and bromine in dichloromethane in the presence of aqueous hydrogen peroxide at a temperature in the range of room temperature to the reflux temperature, wherein said dichloromethane is present in an amount sufficient for substantially dissolving brominated derivatives of said bisphenol A formed thereby, ii) separating the substantially solid-free reaction mixture obtained in step i) into aqueous and organic phases, precipitating tetrabromobisphenol A from the organic phase and isolating said precipitated tetrabromobisphenol A from said organic phase.
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Page/Page column 5-6
(2010/02/17)
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- A PROCESS FOR THE PREPARATION OF TETRABROMOBISPHENOL A
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A process for preparing tetrabromobisphenol A, which comprises: i) reacting bisphenol A and bromine in dichloromethane in the presence of aqueous hydrogen peroxide at a temperature in the range of room temperature to the reflux temperature, wherein said dichloromethane is present in an amount sufficient for substantially dissolving brominated derivatives of said bisphenol A formed thereby, ii) separating the substantially solid-free reaction mixture obtained in step i) into aqueous and organic phases, precipitating tetrabromobisphenol A from the organic phase and isolating said precipitated tetrabromobisphenol A from said organic phase.
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Page/Page column 20-27
(2008/06/13)
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- 1-Benzyl-4-aza-1-azoniabicyclo[2.2.2]octane tribromide as a regenerable and useful reagent for bromination of phenols under mild conditions
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1-Benzyl-4-aza-1-azoniabicyclo[2.2.2]octane tribromide has been examined over several phenolic compounds under mild conditions. The reaction gives brominated phenols in good to excellent yields. Straightforward work-up of the reaction yields pure products in several cases.
- Hajipour, Abdol R.,Pourmousavi, Seied A.,Ruoho, Arnold E.
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p. 796 - 800
(2007/10/03)
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- Method of crystallizing tetrabromobisphenol A
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A method of crystallizing tetrabromobisphenol A is described, which comprises continuously and simultaneously feeding a methanolic tetrabromobisphenol A solution and water separately to a first crystallizer to obtain a slurry in which a part of the tetrabromobisphenol A is crystallized and continuously and simultaneously feeding said slurry and water separately to a second crystallizer to crystallize substantially the whole amount of the tetrabromophisphenol A.
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Page column 14-15, 16-17, 18
(2008/06/13)
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- Eco-friendly method of preparation of high purity tetrabromobisphenol-A
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A highly pure and colorless tetrabromobisphenol-A (TBBPA) possessing melting point in the range of 178-182° C. is prepared in yields of 50-70% in first batch and 90-100% when the spent organic layer is recycled. In this method, the corrosive liquid bromine is displaced by sodium bromide/hydrobromic acid as brominating agent. Further, sodium bromate is used as an oxidizing as well as brominating agent to utilize the hydrobromic acid that is produced during the bromination of bisphenol-A (BPA). The reaction is conducted at 10-15° C. in a mixture of methylene chloride-water or carbon tetrachloride-water in the presence of hydrochloric acid and sodium lauryl sulfate. The crystalline product settled at the bottom of the reaction vessel is filtered, washed, dried and weighed. The spent organic layer is recycled in subsequent batches to maximize the overall yield of product recovered directly as solid and to minimize generation of organic effluent.
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- A controlled and selective bromination of phenols by benzyltriphenylphosphonium tribromide
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Reactions of phenols with benzyltriphenylphosphonium tribromide in dichloromethane-methanol mixture (2:1) gave mono, di and tri brominated phenols at room temperature with high selectivity and good yields.
- Hajipour, Abdol Reza,Mallakpour, Shadpour E.,Imanieh, Hossein,Pourmousavi, Seied A.
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p. 272 - 275
(2007/10/03)
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- Oxidative bromination of bisphenols. Synthesis of 4,4'-isopropylidenebis(2,6-dibromophenol)
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4,4'-Isopropylidenebis(2,6-dibromophenol) was synthesized in 92-96% by reaction of 4,4'-isopropylidenediphenol with bromine taken at a ratio of 1:2 in the presence of 30% hydrogen peroxide.
- Lazarev,Nedolya
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p. 1758 - 1759
(2007/10/03)
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- Bisphosphine oxide monomers
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Bisphosphine oxide monomers and homologs thereof may be incorporated into polycarbonates in order to obtain a flame retardant polymer. More particularly, bis[2,5-(diphenylphosphine oxide)]-1,4-hydroquinone and homologs thereof may be used to prepare flame retardant polycarbonates that retain high glass transition temperature and high impact resistances.
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- Processes for producing aromatic polycarbonate oligomer and aromatic polycarbonate
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A process for producing continuously an aromatic polycarbonate oligomer by reacting an aromatic dihydroxy compound and an alkali metal base or an alkaline earth metal base with a carbonyl halide compound comprises: (1) feeding continuously to a tank reactor an aromatic dihydroxy compound, water, a molecular weight controlling agent, a polymerization catalyst, a carbonyl halide compound, and an organic solvent, and an alkali metal base or an alkaline earth metal base in an amount of 1.15-1.6 equivalents based on the aromatic dihydroxy compound, (2) carrying out the reaction with a residence time as defined by the following formula, where X is an amount of the polymerization catalyst in terms of mole % based on the amount of mole of the aromatic dihydroxy compound fed per unit time, and Y is a residence time (min.), and (3) continuously withdrawing the reaction mixture from the tank reactor to obtain an aromatic polycarbonate oligomer having a number average molecular weight of 1,000-10,000. An aromatic polycarbonate is produced by polycondensation of the aromatic polycarbonate oligomer.
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- Method for preparing aromatic bischloroformate compositions
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Bischloroformate oligomer compositions are prepared by passing phosgene into a heterogeneous aqueous-organic mixture containing at least one dihydroxyaromatic compound, with simultaneous introduction of a base at a rate to maintain a specific pH range and to produce a specific volume ratio of aqueous to organic phase. By this method, it is possible to employ a minimum amount of phosgene. The reaction may be conducted batchwise or continuously. The bischloroformate composition may be employed for the preparation of cyclic polycarbonate oligomers or linear polycarbonate, and linear polycarbonate formation may be integrated with bischloroformate composition formation in a batch or continuous process.
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- Bischoloroformate preparation method with phosgene removal and monochloroformate conversion
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Aqueous bischloroformates are prepared by the reaction of a dihydroxyaromatic compound (e.g., bisphenol A) with phosgene in a substantially inert organic liquid (e.g., methylene chloride) and in the presence of an aqueous alkali metal or alkaline earth metal base, at a pH below about 8. After all solid dihydroxyaromatic compound has been consumed, the pH is raised to a higher value in the range of about 7-12, preferably 9-11, and maintained in said range until a major proportion of the unreacted phosgene has been hydrolyzed. At the same time, any monochloroformate in the product may be converted to bischloroformate.
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- Cyclic monocarbonate bishaloformates
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Cyclic monocarbonate bischloroformates are prepared by the reaction of a carbonyl halide such as phosgene with a bridged substituted resorcinol or hydroquinone such as bis(2,4-dihydroxy-3-methylphenyl)methane or bis(2,5-dihydroxy-3,4,6-trimethylphenyl)methane in the presence of aqueous alkali metal hydroxide. The cyclic monocarbonate bischloroformates may be used for the preparation of linear or cyclic polycarbonates containing cyclic carbonate structural units, which may in turn be converted to crosslinked polycarbonates.
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- Polyetherimide bisphenol compositions
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Polyetherimide bisphenols and bischloroformates are prepared by the reaction of dianhydrides or certain bisimides with aminophenols or mixtures thereof with diamines. They are useful as intermediates for the preparation of cyclic heterocarbonates, which may in turn be converted to linear copolycarbonates. The bisphenols can also be converted to salts which react with cyclic polycarbonate oligomers to form block copolyetherimidecarbonates.
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- Polycarbonates exhibiting improved heat resistance
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Novel heat resistant polycarbonates are provided which are the polymerized reaction products of: (i) a carbonate precursor; and (ii) at least one dihydric phenol selected from dihydric phenols represented by the general formulae STR1 wherein: each R1 is independently selected from halogen radicals, monovalent hydrocarbon radicals, and monovalent hydrocarbonoxy radicals; each R2 is independently selected from halogen radicals, monovalent hydrocarbon radicals, and monovalent hydrocarbonoxy radicals; R4 and R5 are independently selected from monovalent hydrocarbon radicals; R3 is selected from hydrogen and monovalent hydrocarbon radicals, with the proviso that if R3 is a hydrogen radical than at least one of the monovalent hydrocarbon radicals represented by R4 and R5 contains at least two carbon atoms; R7 is selected from hydrogen and monovalent hydrocarbon radicals; R6 is a divalent hydrocarbon radicals; and n and n' are independently selected from whole numbers having a value of from 0 to 4 inclusive.
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- Process for the preparation of bisphenols
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Processes for the preparation of bisphenols from phenols and substituted vicinal glycols, or unsaturated alcohols or substituted dienes resulting in bisphenols represented by the general formula: STR1 wherein: R1 and R2 are independently selected from monovalent hydrocarbon and monovalent hydrocarbonoxy radicals of one to four carbon atoms, or from halogen radicals; R3, R4 and R5 is each a lower alkyl radical, preferably of one to four carbon atoms, aryl radicals, alkaryl radicals, aralkyl radicals, and cycloalkyl radicals, and is the same or different; R5 may also be hydrogen. n and n1 are independently selected from whole numbers having a value of from 0 to 4 inclusive.
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- Process for the production of 4,4-isopropylidene-bis'(2,6-dibromophenol)
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4,4'-isopropylidene-bis(2,6-dibromophenol) is produced by reacting 4,4'-isopropylidene diphenol with hydrogen bromide or a mixture of hydrogen bromide with up to an equimolar amount of free bromine in admixture with hydrogen peroxide and in the presence of water and an inert organic liquid.
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- Process for halogenating a bisphenol
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Halogenated bisphenols, such as 4,4'-isopropylidene-bis(2,6-dibromophenol), can be produced in high purity and high yield by brominating in 75-95 weight per cent aqueous acetic acid, and subsequently heating the reaction mass at 80° - 120° C. for 5-60 minutes. The resultant mixture can be neutralized prior to separating desired product from the reaction mixture.
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