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🥼organic chemistry review

Skeletal Rearrangements

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

Definition

Skeletal rearrangements refer to the process where the carbon skeleton of an organic compound is reorganized, often resulting in the formation of a new structural isomer. This phenomenon is particularly relevant in the context of preparing alkyl halides from alkanes through radical halogenation.

5 Must Know Facts For Your Next Test

  1. Skeletal rearrangements can occur during radical halogenation reactions, where the carbon skeleton of the alkane is reorganized to form a new structural isomer.
  2. These rearrangements are driven by the formation and stability of the intermediate free radicals, which can undergo 1,2-shifts to create more stable configurations.
  3. The extent of skeletal rearrangement depends on factors such as the size of the alkane, the nature of the halogen, and the reaction conditions.
  4. Larger alkanes are more prone to skeletal rearrangements due to the increased stability of the intermediate free radicals formed during the reaction.
  5. Skeletal rearrangements can lead to the formation of branched alkyl halides, which can have different physical and chemical properties compared to the original linear alkanes.

Review Questions

  • Explain the role of free radicals in facilitating skeletal rearrangements during radical halogenation of alkanes.
    • The formation of free radicals is a key step in radical halogenation reactions. These highly reactive species can undergo 1,2-shifts, where the unpaired electron is transferred to an adjacent carbon atom, resulting in the rearrangement of the carbon skeleton. The stability of the intermediate free radicals plays a crucial role in determining the extent of the skeletal rearrangement, with larger alkanes being more prone to these reorganizations due to the increased stability of the rearranged free radicals.
  • Describe how the nature of the halogen and the reaction conditions can influence the extent of skeletal rearrangements in radical halogenation of alkanes.
    • The choice of halogen and the reaction conditions can impact the likelihood and extent of skeletal rearrangements during radical halogenation. Larger halogens, such as bromine, tend to promote more rearrangements compared to smaller halogens like chlorine, due to the increased stability of the intermediate free radicals. Additionally, factors like temperature, light exposure, and the presence of initiators or catalysts can affect the reaction kinetics and the prevalence of skeletal rearrangements. For example, higher temperatures or the use of UV light can increase the rate of radical formation and propagation, potentially leading to more extensive skeletal reorganization.
  • Analyze the implications of skeletal rearrangements in the context of preparing alkyl halides from alkanes through radical halogenation, and discuss the potential consequences for the physical and chemical properties of the resulting products.
    • Skeletal rearrangements during radical halogenation of alkanes can have significant implications for the properties and reactivity of the resulting alkyl halides. The formation of branched structures, rather than linear ones, can lead to changes in physical properties such as boiling point, melting point, and solubility. Additionally, the altered carbon skeleton can affect the chemical reactivity of the alkyl halides, potentially impacting their subsequent transformations or the selectivity of subsequent reactions. Understanding and predicting the extent of skeletal rearrangements is crucial for controlling the product composition and ensuring the desired properties of the alkyl halides prepared through this method.