Hydrobromic Acid, —Iodine

Dehydration Alumina (see also Dihydropyrane, preparation). Boric acid. Boron triSuoride. N-Bromoacetamide-Pyridine-SOj. Dicyclohexylcarbodiimide. Diketene. Dimethylform-amide-Thionyl chloride. Dimethyl sulfoxide. Ethylene chlorophosphite. Florisil. Girard s reagent. Hydrobromic acid. Iodine. Mesyl chloride-Sulfur dioxide. Methyl chlorosulfite. Methylketene diethylacetal. Naphthalene-d-sulfonic acid. Oxalic acid. Phenyl isocyanate. Phosgene. Phosphorus pentoxide. Phosphoryl chloride. Phthalic anhydride. Potassium bisulfate. Pyridine. Thionyi chloride. Thoria. p-Toluenesulfonic acid. p-Toluenesulfonyl chloride. Triphenylphosphine dibromide. 

Chlorinated derivatives will thus form hydrochloride acid, brominated derivatives hydrobromic acid, iodinated compounds hydriodic acid. Hydrolysis of a chlorinated or brominated derivative will lead to a more intense attack of aluminium than hydrolysis of an iodine derivative. 

Oxaziridines are powerful oxidizing agents. Free halogen is formed from hydrobromic acid (B-67MI50800). Reduction by iodide in acidic media generally yields a carbonyl compound, an amine and two equivalents of iodine from an oxaziridine (1). With 2-alkyl-, 2-acyl and with N-unsubstituted oxaziridines the reaction proceeds practically quantitatively and has been used in characterization. Owing to fast competing reactions, iodide reduction of 2-aryloxaziridines does not proceed quantitatively but may serve as a hint to their presence. 

Chlorination and bromination of chlorins can be carried out with aqueous hydrochloric or hydrobromic acid in the presence of hydrogen peroxide, but also with free chlorine or bromine in solution. Depending on the stoichiometric amount of halogenation agent, mono-or bishalogenated products are selectively formed as in the case of octaethylchlorin 15, Attempts to iodinate chlorins have been unsuccessful. 

The excess of bromine is converted into hydrobromic acid by means of formic acid and, finally, after addition of potassium iodide, the iodine liberated is titrated with thiosulphate. 

G. P. Baxter and F. B. Coffin 4 used this process for preparing hydrobromic acid for their work on at. wt. The hydrobromic acid was condensed in water contained in a cooled flask. In order to remove iodine, the soln. was diluted with water, and twice boiled with a little free bromine. A small quantity of potassium permanganate added, and the bromine set free was expelled by boiling. The acid was finally distilled with the aid of a quartz condenser, and the first third rejected. 

Vanadium lends itself also to iodometric method of determination. The vanadate solution is reduced with hydrobromic acid, excess of potassium iodide is added, and the iodine thereupon liberated is estimated with sodium thiosulpliate solution. The reaction is 3... 

The action is slow with hydrochloric acid, heating under pressure or the use of a dehydrating agent being usually necessary. Hydrobromic acid reacts more easily and hydriodic still more easily. Instead of the acids, bromine and iodine may be allowed to act on the alcohols in presence of phosphorus. For summary, see A. C. R., 1934, 119. 

Hydrazine dihydrochloride, 92 Hydrazine residues, recovery of, 92 Hydrazine sulfate, 90, 92 Hydrazoic acid, 77, 78 Hydriodic acid, 157, 159 by action of iodine on hydrogen sulfide, 157 constant boiling, 158 fuming, 162 stabilization of, 159 Hydrobromic acid, 151, 152, 155 constant boiling, 155... 

In the presence of hydrochloric acid or hydrobromic acid the oxidation of hydriodic acid may proceed further, the iodine being converted into iodic acid possibly by way of iodine trichloride or bromide. However, periodic acid is reduced to iodic acid by hydrogen peroxide and in dilute solution partial reduction even to iodine may occur.10... 

S-Hydfoxy ketones obtained by the condensation of ketones or by the crossed condensation of aldehydes with ketones are important sources of olefinic ketones. Dehydration is effected by warming the ketols with oxalic acid, dilute sulfuric acid, hydrobromic acid, phosphoric acid, or a trace of iodine. A typical example is the dehydration of diacetone alcohol obtained from the self-condensation of acetone. The product is an equilibrium mixture of the conjugated and unconjugated isomers, (CHj)jC=CHCOCHj and CHj=C(CHj)CHjCOCHj, in a ratio of 91 to 9, respectively. ... 

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