Bromide from 8 alcohol

Owing to the corrosive action of bromine upon corks j-jg 7, l. and rubber stoppers, ground glass joints are recommended in this preparation. The apparatus, depicted in Fig. Ill, 37, 1, is particularly convenient for the preparation of bromides from alcohols. A double surface condenser is fitted into D and a round-bottomed flask is fitted on to the ground glass joint at C R is a three-way stopcock f which permits the removal of the contents of A without disconnecting the apparatus. For preparations of moderate size, A has a capacity of 60 or 100 ml. and a 250 or 500 ml. flask is attached at C. 

A considerable amount of hydrobromic acid is consumed in the manufacture of inorganic bromides, as well as in the synthesis of alkyl bromides from alcohols. The acid can also be used to hydrobrominate olefins (qv). The addition can take place by an ionic mechanism, usually in a polar solvent, according to Markownikoff s rule to yield a secondary alkyl bromide. Under the influence of a free-radical catalyst, in aprotic, nonpolar solvents, dry hydrogen bromide reacts with an a-olefin to produce a primary alkyl bromide as the predominant product. Primary alkyl bromides are useful in synthesizing other compounds and are 40—60 times as reactive as the corresponding chlorides (6). 

DIMETHYL-3-PHENYLPRO-PIONALDEHYDE, 54, 46 Alkylboranes, oxidation, 52, 59 synthesis, 52, 59 Alkyl bromides, from alcohols, 54, 66... 

Alkyl bromides, from alcohols, benzyl bromide, and triphenyl phosphite,... 

Akylation, of acids, 50, 61 by oxonium salts, 51,144 Alkyl bromides, from alcohols, benzyl bromide, and triphenyl phosphite,... 

Hydrobromic acid is used in the preparation of inorganic bromide salts. The acid also is used for many organic syntheses, including alkyl bromides from alcohols or olefins, and bromophenols from phenols. The compound also is used as an acid catalyst in many alkylation, selective oxidation, isomerization, and dehydrogenation reactions. Other apphcations are in extraction of minerals and use as a reducing agent. 

The Mitsunobu reaction was discussed in Chapter 17, p. 000. Mitsunobu chemistry involves using a phosphorus atom to remove the OH group, after the style of PBrs as a reagent to make alkyl bromides from alcohols. 

Hydrogen bromide is used as a reagent and catalyst in several types of organic reactions such as the formation of alkyl bromides from alcohols. 

Introduction. The Ph3PBr2 adduct was first used in synthesis in 1959 for the preparation of alkyl and acyl bromides from alcohols and carboxylic acids, and for the dehydration of amides and oximes to nitriles. Since then it has been widely employed as a versatile reagent for a number of synthetic reactions. 

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