Reaction with hydrogen bromide

Bromination of methane is exothermic but less exothermic than chlorination The value calculated from bond dissociation energies is AH° = -30 kJ Al though bromination of methane is energetically fa vorable economic considerations cause most of the methyl bromide prepared commercially to be made from methanol by reaction with hydrogen bromide... 

The reactions of halogens and hydrogen halides with alkenes are electrophilic addition reactions. This means that the initial attack on the organic molecule is by an electron-deficient species that accepts a lone pair of electrons to form a covalent bond. This species is called an electrophile. In the case of the reaction with hydrogen bromide, the mechanism for the reaction is as shown. 

However, when the pentachloride is heated with hydrocarbons, a beta-form of M0CI4 forms. The product always is contaminated with carbon. Heating the pentachloride with molybdenum metal forms the same beta-MoCR. Reaction with hydrogen bromide yields molybdenum tetrabromide. 

The structure of allyl bromide (3-bromo-l-propene) is CH2=CHCH2Br. Its reaction with hydrogen bromide in accordance with Markovnikov s rule proceeds by addition of a proton to the doubly bonded carbon that has the greater number of attached hydrogens. 

All three alcohol functions are converted to bromide by reaction with hydrogen bromide in step 2. Step 2 ... 

The Leukart reaction has also been used in the conversion of dehydroepiandro-sterone into 17/3-formylamino-3/3-formyloxyandrost-5-ene, which on reduction with lithium aluminium hydride afforded 3/3-hydroxy-17/3-me thylaminoandrost-5-ene. Acylation with isocaproyl chloride then furnished the N-methyl-N-isocaproyl steroid (197), after selective ester hydrolysis of the initially formed ON-diacyl derivative. The amide (197) was further converted into its 3,5-cyclo-6-ketone via the 3,5-cyclo-6/3-alcohol and thence by reaction with hydrogen bromide into the corresponding 3/3-bromo-5a-6-ketone which upon dehydrobromination furnished a A2-5a-6-ketone and ultimately the 2-monoacetate of the 2/3,3/3-diol (198) after reaction with silver acetate and iodine. Hydrolysis to the 2/3,3/3-diol (198) gave a separable mixture of the 2/3,3/8-dihydroxy-5a- and -5/3-ketones.88... 

Reactions with hydrogen bromide or hydrogen iodide generally occur at room temperature, whereas the addition of hydrogen chloride may require heat. Benzene, pentane, and ether are employed as solvents. 

REACTION WITH HYDROGEN BROMIDE The stoichiometry of this reaction is similar to that of HCI, viz. 

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