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🥼organic chemistry review

Cyclic Alkenes

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

Cyclic alkenes are unsaturated cyclic organic compounds that contain at least one carbon-carbon double bond within a ring structure. These compounds are an important class of molecules in organic chemistry, particularly in the context of understanding the addition of water (hydration) to alkenes through the process of hydroboration-oxidation.

5 Must Know Facts For Your Next Test

  1. Cyclic alkenes exhibit unique reactivity due to the strain and angle of the ring structure, which can influence the ease of addition reactions.
  2. The presence of the carbon-carbon double bond in cyclic alkenes makes them susceptible to electrophilic addition reactions, such as hydroboration-oxidation.
  3. The hydroboration step in the hydroboration-oxidation reaction of cyclic alkenes involves the regioselective addition of the borane reagent, typically adding to the less hindered carbon of the double bond.
  4. The subsequent oxidation step in the hydroboration-oxidation reaction of cyclic alkenes converts the organoborane intermediate into an alcohol product, with the hydroxyl group being added to the more substituted carbon of the original double bond.
  5. The hydroboration-oxidation of cyclic alkenes can be a useful synthetic tool for the preparation of cyclic alcohols, which are important building blocks in organic synthesis.

Review Questions

  • Explain the role of the cyclic structure in the reactivity of cyclic alkenes during the hydroboration-oxidation reaction.
    • The cyclic structure of cyclic alkenes can influence their reactivity during the hydroboration-oxidation reaction. The strain and angle of the ring can affect the ease of addition of the borane reagent, leading to regioselectivity in the hydroboration step. Additionally, the cyclic nature of the molecule can impact the subsequent oxidation step, determining the position of the resulting hydroxyl group on the final alcohol product.
  • Describe the mechanism of the hydroboration-oxidation reaction as it applies to cyclic alkenes, highlighting the key steps and the factors that govern the regio- and stereochemistry of the product.
    • The hydroboration-oxidation reaction of cyclic alkenes involves two main steps. In the first step, the borane reagent (BH3) adds to the carbon-carbon double bond in a regioselective manner, typically adding to the less hindered carbon. This forms an organoborane intermediate. In the second step, the organoborane is oxidized, converting the boron-containing group into a hydroxyl group. The position of the hydroxyl group on the final alcohol product is determined by the regioselectivity of the initial hydroboration step, with the hydroxyl group being added to the more substituted carbon of the original double bond.
  • Evaluate the synthetic utility of the hydroboration-oxidation reaction of cyclic alkenes, discussing how this transformation can be used to prepare important cyclic alcohol building blocks for organic synthesis.
    • The hydroboration-oxidation reaction of cyclic alkenes is a valuable synthetic tool for the preparation of cyclic alcohol products. These cyclic alcohols can serve as important building blocks in organic synthesis, as they can be further functionalized or incorporated into more complex molecular structures. The ability to control the regio- and stereochemistry of the hydroxyl group addition through the hydroboration-oxidation sequence makes this reaction particularly useful for the targeted synthesis of desired cyclic alcohol products. Additionally, the hydroboration-oxidation of cyclic alkenes can be a convenient way to introduce oxygen functionality into cyclic systems, expanding the synthetic toolbox for organic chemists.