Salts bromide

Another halogenated photolysis (30), using carbon tetrabromide to produce hydrogen bromide and subsequent reaction with spiropyran (5), produces a highly colored spiropyrilium bromide salt. 

Catalysts other than the above cobalt salts have been considered. Several patents suggest that cobalt bromide gives improved yields and faster reaction rates (12—16). The bromide salts are, however, very corrosive and require that expensive materials of constmction, such as HastaHoy C or titanium, be used in the reaction system. Only one faciHty, located in the UK, is beHeved to uti1i2e cobalt bromide catalyst in the production of ben2oic acid. 

The stereochemistry of addition is usually anti for alkyl-substituted alkynes, whereas die addition to aryl-substituted compounds is not stereospecific. This suggests a termo-iecular mechanism in the alkyl case, as opposed to an aryl-stabilized vinyl cation mtermediate in the aryl case. Aryl-substituted alkynes can be shifted toward anti addition by including bromide salts in the reaction medium. Under these conditions, a species preceding the vinyl cation must be intercepted by bromide ion. This species can be presented as a complex of molecular bromine with the alkyne. An overall mechanistic summary is shown in the following scheme. 

BrCl can be prepared by the reaction in the gas phase or in aqueous hydrochloric acid solution. In the laboratory, BrCl is prepared by oxidizing bromide salt in a solution containing hydrochloric acid. 

The halogenation of selenazoles goes less smoothly than the nitration and sulfonation. For example the bromination of 2,4-dimethyl-selenazoie with cold bromine first gives an unstable monobromo derivative (mp 168°C). This is transformed easily into a compound of mp 205°C (decomp.) which Haginiwa assumes is the hydrogen bromide salt of 2,4-dimethyl-5-bromoselenazole. 

Although direct nitration was not possible, 2-amino-4-methylselena-zole can be directly brominated by treatment with bromine in carbon tetrachloride, the hydrogen bromide salt of 2-amino-4-methyl-5-bromoselenazole, mp 180°C (decomp.) is formed. However, all attempts to obtain the free base from this salt failed and led to complete decomposition. In this bromination, an equivalent quantity of bromine must be used excess also leads to complete destruction of the molecule. From the decomposition products an oily compound can be detected similar to bromoacetone. ... 

To a solution of 30.7 g (0.203 mol) of 1-phenoxy-2-aminopropane in 150 ml of ethanol there was added 31.9 g (0.100 mol) of 1-(4 -benzyloxyphenyl)-2-bromopropanone-1. The mixture was heated to boiling temperature and the solution was then refluxed in a reflux condenser for 3 hours. Most of the ethanol was then distilled off in vacuo. Then to the residue there was added about 150 ml of diethyl ether. The hydrogen bromide salt of 1-phenoxy-2-aminopropane was filtered off and washed with diethyl ether. 

Table 3.1-3 Changes in melting points for symmetric tetraalkylammonium bromide salts with increasing size of alkyl substituents.

The use of ionic liquids as reaction media for the palladium-catalyzed Heck reaction was first described by Kaufmann et ak, in 1996 [85]. Treatment of bromoben-zene with butyl acrylate to provide butyl trans-cinnamate succeeded in high yield in molten tetraallcylammonium and tetraallcylphosphonium bromide salts, without addition of phosphine ligands (Scheme 5.2-16). 

Absorption type refrigeration using water as a refrigerant and lithium-bromide salts as an absorber. 

In contrast, bromination of dimethyl 3-methyl-3/f-bcnzazepine-2,4-diearboxylate yields only a quaternary bromide salt.24... 

K, = 7.8 X 10 4, is usually marketed as the hydrogen bromide salt, C6H5CH2CH(CH )NH3+Br, because it is much more stable in this solid form. Determine the pH of a solution made from dissolving 6.48 g of the salt to form 200.0 mL of solution. 

Waste HBr is a common byproduct of organic brominations. Frequently, this waste is neutralized with caustic, the resulting sodium bromide salt is discharged, and valuable bromine is lost. The economic advantages of recovery and recycle of this HBr have long been recognized (refs. 1, 3). In practice, recovery typically takes the form of conversion of the HBr to clear drilling fluids or alkylbromides (ref. 4) as shown in equations 1 and 2. 

The most commonly encountered inorganic contaminants in waste HBr streams are primarily low level bromide salts such as sodium bromide or calcium bromide. These do not provide a significant challenge to catalytic performance because they are unlikely to enter the catalytic reactor in significant quantities. Instead, the low operating temperature (about 128°C) of the vaporizer would cause them to be retained and concentrated in that vessel. 

As another example, the tropylium ion [3 ], which is stabilized by virtue of the 67t electrons spread over a heptagonal sp hybridized carbon framework [Hiickel s (4n 4- 2)v rule with = 1], is also unstable in the gas phase. Its formation from toluene or the benzyl cation has been a long-standing problem in organic mass spectrometry, and the reaction mechanism and energetics have recently been exhaustively discussed (Lif-shitz, 1994). It was, however, isolated as the bromide salt by Doering and Knox (1954, 1957), and was the first non-benzenoid aromatic carbocation. 

The oldest anti-anxiety agent is undoubtedly alcohol and it is certain that this drug is still routinely self-administered for this purpose. Towards the end of the eighteenth century, bromide salts were used to relieve conditions akin to anxiety despite the risk of a characteristic toxic delirium, known as bromism . Alternative treatments, such as paraldehyde and chloral hydrate, were also widely used but these too had adverse effects the former can cause psychosis but the latter is still used as a sedative and anaesthetic agent. 

Furan was dimethoxylated to give 2,5-dihydro-2,5-dimethoxyfuran, using electrogenerated bromine molecules generated from bromide salts in electrolyte solutions [71]. This reaction was characterized in classical electrochemical reactors such as pump cells, packed bipolar cells and solid polymer electrolyte cells. In the last type of reactor, no bromide salt or electrolyte was used rather, the furan was oxidized directly at the anode. H owever, high consumption of the order of 5-9 kWh kg (at 8-20 V cell voltage) was needed to reach a current efficiency of 75%. 

Although thiosemicarbazones which have a N-hydrogen seem to yield a variety of nickel(II) centers depending on the nature of the alkyl group attached at N, the Af-dialkyl- [137] and C-azabicyclothiosemicarbazones [139, 140] studied to date all yield brown, diamagnetic [Ni(L-H)Cl] complexes. With the exception of [Ni(10)2Br]Br [139], the bromide salts have also yielded diamagnetic [Ni(L-H)Br] complexes. 

The acetoxy group is introduced exclusively at the benzylic carbon. This is in accord with the intermediate being a weakly bridged species or a benzylic cation. The addition of bromide salts to the reaction mixture diminishes the amount of acetoxy compound formed by shifting the competition for the electrophile in favor of the bromide ion. Chlorination in nucleophilic solvents can also lead to solvent incorporation, as, for example, in the chlorination of 1-phenylpropene in methanol.37... 

The rate and selectivity of the reaction can be considerably enhanced by using an added quaternary bromide salt in 1 1 TFA CH2C12. Note that the reactions are quite... 

The reactions are accelerated by bromide salts, which are thought to exchange for acetate in the ir-allylic complex. The reactions of acyclic compounds occur with minimal E Z isomerization. This result implies that the TT-allyl intermediate is captured by carbonylation faster than E Z isomerization occurs. 

Solutions of the alkylammonium salts of Cl , Br , r in acetonitrile show no visible absorptions beyond 300 nm. The aromatic it-acceptor, tetracyanopy-razine (TCP) is characterized by strong absorptions in the 220-300 nm range and a shoulder at 350 nm. However, the electronic spectrum of a mixture of the bromide salt and TCP reveals a new absorption band at Xct = 400 nm... 

A number of amidines have anthelmintic activity. Bunamidine (25), indicated for treatment of human pinworm infestations, is prepared from a-naphthylhexyl-ether (23) by Friedel-Crafts type reaction with cyanogen bromide and aluminum chloride to give nitrile (24). This, then, is reacted with the magnesium bromide salt of di-n-propylamine leading to the naph-thamidine structure (25). -... 

Interaction of lead oxide with bromide salts in phenol at the ratio Br PbO less than 2 yields the precipitation of white sediments with the general formula PbnOm(OPh)(2.z)(n-m)Brz(n-m), where n = 4 - 10, m = 1 - 4, z = 0 - 1 and formation of (n-m) moles of water. Reaction takes place in the presence of a variety of bromide salts including quaternary and alkali metal bromides. In the latter case, the presence of acoordinating solvent, e.g. MeCN, is necessary. The composition of product lead bromophenoxides depends on the Br PbO ratio, bromide salt and solvent. These complexes usually have Pb 0 ratio of 4 1 or 3 1, and variable levels of bromide (including some bromide-free complexes) (Table 3). 

Cobalt bromide is used as a catalyst in the technology of production of arylcarboxylic acids by the oxidation of methylaromatic hydrocarbons (toluene, p-xylene, o-xylene, polymethyl-benzenes). A cobalt bromide catalyst is a mixture of cobaltous and bromide salts in the presence of which hydrocarbons are oxidized with dioxygen. Acetic acid or a mixture of carboxylic acids serves as the solvent. The catalyst was discovered as early as in the 1950s, and the mechanism of catalysis was studied by many researchers [195-214],... 

Crystalline solid. Bromide salt is a hygroscopic white solid. Various other salts have been reported. 

Synthesis using Gemini surfactant (bromide salt of... 

Reaction of Various Aldimine and Ketimine Magnesium Bromide Salts with Alkylating Agents in Tetrahydrofuran... 

These results show that cyclohexenyl iodonium salt readily gives cyclohexenyl cation under poorly nucleophilic/basic conditions. When a stronger nucleophile like bromide is added to the solution of 3, 1-bromocyclohexene 13 is formed as a main product (eq 5). It is noteworthy here that the rate of the reaction is strongly retarded by the added bromide salt as a nucleophilic reagent (Figure 1), although bromide does react with the substrate to give substitution product 13.6... 

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