Addition of hydrogen halide to unsaturated alcohols, ethers, carbonyl compounds, and nitriles

Addition of hydrogen halide to unsaturated alcohols, ethers, carbonyl compounds, and nitriles 

The OH group is completely or partially replaced by halogen when HC1 or HBr adds to an unsaturated alcohol unless that OH group is separated from the C=C unit by several carbon atoms. For example, the OH is replaced by Cl or Br when cinnamyl alcohol reacts with gaseous HC1 at 0° or with HBr in glacial acetic acid.199 

An intermediate esterification is required to achieve anti-Markovnikov addition of HBr to higher unsaturated alcohols. For instance, even when a peroxide is added, 10-undecen-l-ol and HBr afford 10-bromo-l-undecanol, whereas HBr adds to 10-undecenyl acetate in the presence of peroxides so that the bromine appears in the 11-position whereas in the presence of antioxidants (H2 and diphenylamine) it appears in the 10-position.200 The HBr adducts obtained from the acetates in the presence of dibenzoyl peroxide can be converted into the bromo alcohols by transesterification with methanol and / -toluenesulfonic acid.201 11-Bromo-1-undecanol, 13-bromo-l-tridecanol, and 15-bromo-l-pentadecan ol can also be obtained by intermediate conversion of the corresponding co-unsaturated alcohols into the boric esters. 

HBr is led into a solution of the boric ester containing di-ter/-butyl peroxide at 0-2°, then at least half of the solvent (toluene) is distilled off, and the ester is hydrolysed by addition of water and stirring for an hour at 50°.202 

Addition of HC1 or HBr to phenyl or alkyl vinyl ethers, leading to -halo-alkyl ethers, must be carried out at low temperatures (—5 to +5°), otherwise polymerization occurs. 

---