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Can occur either in syn or anti addition fashion depending on the specific mechanism followed. If osmium tetroxide is used, hydroxide groups are added in syn fashion. If an epoxide mechanism is followed, hydroxide groups are added in an anti fashion. Neither Markovnikov or anti-Markovnikov because the substituents are the same. Hydrobromination
The anti-Markovnikov rule can be illustrated using the addition of hydrogen bromide to isobutylene in the presence of benzoyl peroxide or hydrogen peroxide. The reaction of HBr with substituted alkenes was prototypical in the study of free-radical additions. Early chemists discovered that the reason for the variability in the ratio of ...
Hydroboration–oxidation is an anti-Markovnikov reaction, with the hydroxyl group attaching to the less-substituted carbon. The reaction thus provides a more stereospecific and complementary regiochemical alternative to other hydration reactions such as acid-catalyzed addition and the oxymercuration–reduction process.
The reaction follows Markovnikov's rule (the hydroxy group will always be added to the more substituted carbon). The oxymercuration part of the reaction involves anti addition of OH group but the demercuration part of the reaction involves free radical mechanism and is not stereospecific, i.e. H and OH may be syn or anti to each other. [2] [3] [4]
This significant rate difference in producing di- and tri-alkyl boranes is useful in the synthesis of bulky boranes that can enhance regioselectivity. In terms of regiochemistry, hydroboration is typically anti-Markovnikov , i.e. the hydrogen adds to the most substituted carbon of the double bond.
The reaction results in an anti-Markovnikov addition of a thiol compound to an alkene. Given the stereoselectivity, high rate and yields, this synthetically useful reaction may underpin future applications in material and biomedical sciences.
Hydrosilylation of alkenes usually proceeds via anti-Markovnikov addition, i.e., silicon is placed at the terminal carbon when hydrosilylating a terminal alkene; [1] however, in the recent years, Markovnikov addition has become a growing field of research.
In the presence of peroxides, HBr adds to a given alkene in an anti-Markovnikov addition fashion. Regiochemistry follows from the reaction mechanism, which exhibits halogen attack on the least-hindered unsaturated carbon.