Which reaction have anti addtion oxymercution demercuration or hydrobo...
Introduction:
The reactions of oxymercuration-demercuration and hydroboration-oxidation are important organic transformations used in synthetic chemistry. Both reactions have distinct mechanisms and result in different products. In this response, we will discuss each reaction in detail, including their mechanisms and the products they yield.
Oxymercuration-Demercuration:
This reaction involves the addition of an alcohol group (-OH) to an alkene using mercury (II) acetate and water. Here is a detailed explanation of the reaction:
1. Oxymercuration:
- The alkene reacts with mercury (II) acetate (Hg(OAc)2) in the presence of a solvent such as water or an alcohol.
- This step proceeds through a concerted mechanism, where the electrons from the π-bond attack the electrophilic mercury ion, forming a cyclic mercurinium ion intermediate.
- The nucleophilic water molecule then adds to the mercurinium ion, resulting in the formation of a stable organomercury compound.
2. Demercuration:
- In this step, a reducing agent such as sodium borohydride (NaBH4) or potassium iodide (KI) is added to the reaction mixture.
- The reducing agent donates electrons to the mercury atom, causing it to lose its bond with the carbon atom and form a stable Hg(0) species.
- The resulting intermediate undergoes hydrolysis, leading to the formation of an alcohol group (-OH) at the site of the original double bond.
Hydroboration-Oxidation:
This reaction involves the addition of an alcohol group (-OH) to an alkene using borane (BH3) as the hydroborating agent, followed by oxidation. Here is a detailed explanation of the reaction:
1. Hydroboration:
- The alkene reacts with borane (BH3) in the presence of a solvent such as tetrahydrofuran (THF).
- The reaction proceeds through a two-step mechanism: (a) the alkene coordinates with BH3 to form a cyclic intermediate called a borane complex, and (b) the borane complex undergoes a concerted insertion reaction, resulting in the formation of an alkylborane intermediate.
2. Oxidation:
- The alkylborane intermediate is oxidized by a peroxide, such as hydrogen peroxide (H2O2) or sodium peroxide (Na2O2).
- This step involves the formation of an alkylperoxide intermediate, which quickly decomposes to yield an alcohol group (-OH) and a borate ester.
- The borate ester is then hydrolyzed to produce the corresponding alcohol.
Conclusion:
In summary, the oxymercuration-demercuration reaction involves the addition of an alcohol group to an alkene using mercury (II) acetate and water, followed by reduction. On the other hand, the hydroboration-oxidation reaction involves the addition of an alcohol group to an alkene using borane as the hydroborating agent, followed by oxidation. These reactions have different mechanisms and lead to the formation of distinct products.
Which reaction have anti addtion oxymercution demercuration or hydrobo...
Oxymercution and demercution is Anti addition where as Hydroboration oxidation is syn addition
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