Addition reaction hydrobromic acid

The addition of a catalytic amount of hydrobromic acid was frequently found to be necessary to initiate the reaction, especially if the phosphorus tribromide is of high purity. Upon addition of the hydrobromic acid, the reaction warms noticeably. 

In the preparation of bromo compounds by the Sandmeyer reaction, the amine is generally diazotised in sulphuric acid solution (or in hydrobromic acid solution), and the resulting aryldiazonium sulphate (or bromide) is treated with a solution of cuprous bromide in excess of hydrobromic acid the addition... 

The basic premise for making bromosafrole has been to mix sa-frole with Hydrobromic Acid (a.k.a. hydrogen bromide, HBr). That s it. The HBr does what is called a Markovnikov addition reaction whereby the HBr sees the allyl double bond of safrole and preferentially attaches its hydrogen to the gamma carbon and its bromine to the middle beta carbon (don t ask). 

Hydrogen bromide adds to acetylene to form vinyl bromide or ethyHdene bromide, depending on stoichiometry. The acid cleaves acycHc and cycHc ethers. It adds to the cyclopropane group by ring-opening. Additions to quinones afford bromohydroquinones. Hydrobromic acid and aldehydes can be used to introduce bromoalkyl groups into various molecules. For example, reaction with formaldehyde and an alcohol produces a bromomethyl ether. Bromomethylation of aromatic nuclei can be carried out with formaldehyde and hydrobromic acid (6). 

Ethylene bromohydrin has been prepared by the reaction between ethylene glycol and hydrobromic acid and phosphorus tribromide. It has also been prepared by the direct addition of hypobromous acid to ethylene, and by the reaction between ethylene and dilute bromine water. With ethylene oxide now available at a reasonable price, the method described is probably the best because of the high yields and the convenience of reaction. 

Thebaine is dissolved in aqueous formic acid and treated with 30% HjO neutralization with aqueous ammonia gives 14-hydroxycodeinone. It is hydrogenated to give oxycodone. 90 ml of concentrated hydrobromic acid are heated to 90°C. 9 grams of 14-hydroxydi-hydrocodeinone (oxycodone) are then added under stirring and the mixture is quickly heated to 116°C and kept at this temperature under reflux condenser for 20 minutes, with continued stirring. The resulting brown solution Is diluted with about 90 ml of water and chilled with ice. Aqueous 10% sodium hydroxide solution is now added to alkaline reaction and the liquid is extracted 3 times with 100 cc portions of chloroform. The layers are separated and the aqueous phase is fiitered and acidified by the addition of concentrated aqueous hydrochloric acid, treated with charcoal and filtered. 

As illustrated in Figure 12, the reaction mixture contains mono-, di-, and tri-brominated glycols, hydrobromic acid, and water. The mixture is extremely corrosive, and the reactor is operated at a temperature just above the freezing point of the product. The key to successfully sampling this mixture was the use of a corrosion-resistant tantalum sampling system. In addition, the sample line was continuously flushed with reactor solvent except during sampling. 

Mediated by Tin. In 1983, Nokami et al. observed an acceleration of the reaction rate during the allylation of carbonyl compounds with diallyltin dibromide in ether through the addition of water to the reaction mixture.74 In one case, by the use of a 1 1 mixture of ether/water as solvent, benzaldehyde was allylated in 75% yield in 1.5 h, while the same reaction gave only less than 50% yield in a variety of other organic solvents such as ether, benzene, or ethyl acetate, even after a reaction time of 10 h. The reaction was equally successful with a combination of allyl bromide, tin metal, and a catalytic amount of hydrobromic acid. In the latter case, the addition of metallic aluminum powder or foil to the reaction mixture dramatically improved the yield of the product. The use of allyl chloride for such a reaction,... 

In addition to the chemical reactions employed in connection with the degradation reaction, which will be discussed later in detail, it should be mentioned that the nitriles can be transformed into amides (XXV) by treatment with hydrobromic acid in glacial acetic acid, a reaction first applied by ZempMn and Kiss to pentaacetyl-n-glucononitrile (XXIV), and also used by subsequent workers. ... 

Bromination of (1) leads to the tetrabromide which, when treated with base, forms 4,7-dibromo-2,1,3-benzothiadiazole <70RCR923>. It was subsequently demonstrated that the 4,6-dibromo (20%) and a trace of the 4,5-dibromo derivatives are also produced in this reaction <70JHC629>. In the presence of iron, bromination of a melt of (1) yields almost exclusively the 4,7-dibromo derivative even when equimolar quantities of bromine are used. As in the chlorination of (1), the process under these conditions cannot be limited to monosubstitution <70RCR923>. Monobromination and subsequent dibromination can be achieved, however, when the reaction is carried out by dropwise addition of bromine to (1) in 47% hydrobromic acid at 130°C <70JHC629>. 

The bromide, [Rh(NH3)6]Br3, is prepared by the addition of concentrated hydrobromic acid to a solution of the chloride or the nitrate. It crystallises in thin hexagonal plates, and is less soluble than the chloride, which it resembles in reactions. 

With the alkali bromides and alkyl ammonium bromides selenium tetrabromide can form crystalline additive compounds of the type MaSeBr6, termed selenibromides. Indeed, by the action of bromine on finely divided selenium in the presence of concentrated hydrobromic acid, a solution is obtained 4 which gradually deposits deep red crystals of hydrogen selenibromide, HaSeBr6. The solution of this body in hydrobromic acid on dilution with water undergoes decomposition with liberation of colloidal selenium. Two reactions probably occur concurrently ... 

A17(20)-Olefin Formation via Favorski Rearrangement149 To a solution of 10 g of 3j3-hydroxypregn-5-en-20-one acetate in 200 ml of acetic acid is added 28.5 ml of a 1 M solution of bromine in acetic acid. After the addition of a few drops of 40% hydrobromic acid, an additional 57 ml of the bromine solution is added. Solid material starts precipitating upon addition of the last mole of bromine, and heating to 40° is necessary to cause complete reaction. The mixture is allowed to stand at room temperature for 2.5 hr, and the solid is filtered and washed with ether to give 15 g (63 %) of 5a,6/ ,17a, 21 -tetrabromo-3/ -hydroxypregnan-20-one acetate mp 172° (dec.). 

After the addition of the bromine is complete, the reaction mixture is allowed to stand at room temperature for about one hour. It then has a light-yellow color. The solution is washed with water and then with two 500-cc. portions of 20 per cent sodium hydroxide solution to remove any dissolved hydrobromic acid. The solution is dried over calcium chloride and filtered. The carbon tetrachloride is distilled through a good column until the temperature at the top of the column reaches about 120°. 

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