DIBAL-H

Definition

DIBAL-H, or diisobutylaluminum hydride, is a powerful reducing agent commonly used in organic chemistry, especially for the selective reduction of carbonyl compounds to their corresponding alcohols. It is particularly effective in reducing esters and aldehydes while leaving ketones largely unaffected. Its unique reactivity makes it a valuable tool in transforming carboxylic acids into alcohols without affecting other functional groups.

5 Must Know Facts For Your Next Test

1. DIBAL-H is particularly useful for converting esters and nitriles into aldehydes, which are intermediates in various synthetic pathways.
2. The reduction with DIBAL-H is typically performed at low temperatures, such as -78°C, to control the reaction and prevent over-reduction.
3. DIBAL-H can be used in both stoichiometric and catalytic amounts depending on the specific needs of the reaction.
4. The reagent is highly reactive with water and moisture, necessitating careful handling and use under an inert atmosphere.
5. After the reduction with DIBAL-H, it is often necessary to work up the reaction mixture with aqueous workup to obtain the final alcohol product.

Review Questions

• How does DIBAL-H selectively reduce carbonyl compounds compared to other reducing agents?
  • DIBAL-H selectively reduces carbonyl compounds due to its unique structure and reactivity. Unlike stronger reducing agents that may reduce both aldehydes and ketones indiscriminately, DIBAL-H can be controlled to preferentially reduce esters to aldehydes. This selectivity is achieved by conducting the reaction at low temperatures, which helps maintain the integrity of more reactive carbonyl compounds while still achieving the desired reduction.
• Discuss the role of temperature in controlling the reduction process when using DIBAL-H.
  • Temperature plays a crucial role in the reduction process with DIBAL-H. Lowering the reaction temperature, typically to -78°C, helps manage the reactivity of the reagent and allows for selective reduction. At these lower temperatures, DIBAL-H can effectively reduce esters to aldehydes without further reducing them to alcohols. This careful temperature control ensures that undesired side reactions are minimized and that the desired products are obtained efficiently.
• Evaluate how DIBAL-H contributes to synthetic strategies in organic chemistry, particularly regarding carboxylic acids.
  • DIBAL-H significantly contributes to synthetic strategies in organic chemistry by enabling chemists to convert carboxylic acids into valuable alcohols while preserving other functional groups. Its ability to selectively reduce functional groups under mild conditions allows for more complex synthetic routes without unwanted side reactions. The use of DIBAL-H not only simplifies the synthesis of alcohols but also opens up pathways for creating intricate molecular architectures through further transformations of the resulting aldehydes and alcohols.

Related terms

Carbonyl Compounds: Organic compounds that contain a carbon atom double-bonded to an oxygen atom, including aldehydes, ketones, and carboxylic acids.

Selective Reduction: A process in organic synthesis where specific functional groups are reduced while others remain unchanged.

Aluminum Hydrides: A class of reducing agents that include DIBAL-H, which are known for their ability to donate hydride ions to a variety of electrophiles.