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Learning Outcomes
i. Recall and write balanced chemical equations for the reaction of KMnO4 with alkenes and alkynes.
ii. Explain the oxidative nature of potassium permanganate and its role in organic transformations.
iii. Identify and name the reagents and products involved in the reaction of KMnO4 with hydrocarbons.
iv. Understand the conditions required for KMnO4 to react with alkenes and alkynes.
Introduction
In the previous lesson, we explored the realm of halogenation reactions, where halogens add to hydrocarbons, giving rise to a wide array of organic compounds. In this final lesson, we venture into the world of oxidation reactions, where potassium permanganate (KMnO4), a powerful oxidizing agent, reacts with alkenes and alkynes, transforming their structural features and properties.
i. Potassium Permanganate: A Versatile Oxidizing Agent
Potassium permanganate, also known as permanganate, is an inorganic compound with the formula KMnO4. It is a strong oxidizing agent, meaning it has a tendency to accept electrons from other compounds. This oxidizing ability makes KMnO4 a versatile reagent in various organic reactions.
ii. Reaction of KMnO4 with Alkenes: Breaking the Double Bond
Alkenes, characterized by their carbon-carbon double bond, readily undergo oxidation reactions with KMnO4. The reaction typically involves the addition of water (H2O) and the cleavage of the double bond, resulting in the formation of vicinal diols (alkane-1,2-diols).
iii. Conditions for KMnO4 Reaction with Alkenes:
Alkaline medium: The reaction is typically carried out in an alkaline medium, such as sodium hydroxide (NaOH) solution, to facilitate the deprotonation of the intermediate alkene epoxide.
Temperature: The reaction is usually conducted at room temperature or slightly elevated temperatures.
iv. Reaction of KMnO4 with Alkynes: Breaking the Triple Bond
Alkynes, with their carbon-carbon triple bond, exhibit even higher reactivity than alkenes and undergo oxidation with KMnO4 to form various products depending on the reaction conditions.
v. Conditions for KMnO4 Reaction with Alkynes:
Acidic medium: The reaction is typically carried out in an acidic medium, such as dilute sulfuric acid (H2SO4), to facilitate the deprotonation of the intermediate alkyne epoxide.
Temperature: The reaction is usually conducted at room temperature or slightly elevated temperatures.
The reaction of KMnO4 with alkenes and alkynes showcases the versatility of this oxidizing agent in organic transformations. By understanding the oxidative nature of KMnO4, the reaction conditions, and the products formed, we gain insights into the reactivity of these unsaturated hydrocarbons and the diverse range of organic compounds that can be synthesized from them.
