Hydrogen Peroxide

Definition

Hydrogen peroxide (H2O2) is a colorless, slightly viscous liquid that is a common oxidizing agent used in a variety of chemical reactions. It is an important compound that plays a role in several organic chemistry topics, including the hydration of alkenes, oxidation of alkenes, hydration of alkynes, preparation of alcohols, and reactions of carboxylic acids.

5 Must Know Facts For Your Next Test

1. Hydrogen peroxide is a powerful oxidizing agent that can be used to cleave alkenes to produce carbonyl compounds through the process of ozonolysis.
2. In the hydroboration-oxidation of alkenes, hydrogen peroxide is used as the oxidizing agent to convert the borane-alkene intermediate to an alcohol.
3. Hydrogen peroxide is used in the final step of the Grignard reaction to convert the organometallic intermediate to an alcohol.
4. The hydration of alkynes can be achieved using mercury(II) salts and hydrogen peroxide to produce carbonyl compounds.
5. Hydrogen peroxide is a common reagent used in the oxidation of alcohols to carboxylic acids, a key step in the preparation of many organic compounds.

Review Questions

• Explain the role of hydrogen peroxide in the hydroboration-oxidation of alkenes.
  • In the hydroboration-oxidation of alkenes, hydrogen peroxide is used as the oxidizing agent in the second step of the reaction. After the initial hydroboration step, where a borane reagent is added to the alkene, the resulting organoborane intermediate is then oxidized using hydrogen peroxide and a base, such as sodium hydroxide. This oxidation converts the organoborane to an alcohol, completing the overall transformation of the alkene to an alcohol.
• Describe how hydrogen peroxide is used in the ozonolysis of alkenes to produce carbonyl compounds.
  • Ozonolysis is a reaction that cleaves alkenes to produce carbonyl compounds. In this process, the alkene is first treated with ozone, which forms an unstable intermediate called a molozonide. This molozonide is then reduced using hydrogen peroxide, which converts it to two carbonyl compounds. The hydrogen peroxide acts as a reducing agent, breaking down the molozonide and allowing the formation of the final carbonyl products.
• Analyze the importance of hydrogen peroxide in the preparation of alcohols using Grignard reagents.
  • Grignard reagents are versatile organometallic compounds used in the synthesis of alcohols. In the final step of the Grignard reaction, the Grignard intermediate is quenched with hydrogen peroxide. This oxidation step converts the organometallic species to an alcohol product. The use of hydrogen peroxide is crucial because it provides the necessary oxygen atom to form the hydroxyl group of the alcohol, while also regenerating the magnesium salt. This final oxidation step is a key part of the overall Grignard reaction for the preparation of a wide range of alcohols.

Related terms

Hydroboration-Oxidation: A two-step reaction that converts alkenes to alcohols, involving the addition of a borane reagent followed by oxidation with hydrogen peroxide and base.

Ozonolysis: A reaction that cleaves alkenes to produce carbonyl compounds, using ozone and then reducing the intermediate with hydrogen peroxide.

Grignard Reagent: An organometallic compound used in the preparation of alcohols, where the reaction with an aldehyde or ketone is quenched with hydrogen peroxide.