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Radical Stability

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Key Questions

  • Radical stability refers to the energy level of the radical.

    If the internal energy of the radical is high, the radical is unstable. It will try to reach a lower energy level.

    If the internal energy of the radical is low, the radical is stable. It will have little tendency to react further.

    Free radicals have only 7 electrons in their valence shell. They are higher in energy than atoms with 8 valence electrons.

    Carbocations are also electron-deficient species. They are even higher in energy, because they have only 6 valence electrons.

    Electron-donating alkyl groups stabilize carbocations. They also stabilize free radicals.

    So the order of stability of free radicals is the same as for carbocations:

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    This means that tertiary radicals are most easily formed, and methyl radicals are least easily formed.

  • Answer:

    Here's a method to figure out stability of intermediates.

    Explanation:

    This method will help you in figuring out stability of all types of intermediate be it carbocation, carbanion or carbon free radical.
    Just think of carbon atom as a person who neither happy with more electron density nor with less. It just needs the right amount of electrons. A free radical has one electron less than Carbon atom. So it needs to compensate for the loss of one electron.

    The increasing order for this stability order is

    Benzylic carbon > Allylic carbon > Tertiary carbon > Secondary carbon > Primary carbon.

  • Radicals are most stabilized by two things:

    1. Hyperconjugation, or

    2. Resonance

    The former delocalizes electron density from adjacent #C-H# bonds, and the latter delocalizes the radical electron around a molecule.

    I'll refer you to another one of my answers to explain the first concept, because students find it hard to understand, generally.

    https://socratic.org/questions/how-does-the-stability-of-carbocation-is-related-with-the-stability-of-free-radi

Questions

  • Maya answered · 10 months ago