11: Intro to Radicals

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Introduction to Radicals

Radicals are species that have single (unpaired) electrons. Many oxidations occur through radical intermediates.

Calculate the formal charge on carbon in each of the following species.
Circle the species that has an unpaired electron.

Radicals are very reactive. They can undergo electron transfer. They also frequently “steal” electrons from other compounds by forming a new bond.

Note the use of a “half-arrow” to illustrate movement of one electron.

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Describe what happens to the electrons in the O-H bond in the reaction.

In the illustration above, R has gained an extra electron (and a proton) in a “hydrogen atom abstraction”. However, oxygen has become a radical.

Show curved arrows and the products of hydrogen atom abstraction from water by the following radicals.

Like other reactive species, radicals can be stabilized through delocalization.

Show how the following radical is stabilized.

Radicals form in many ways, but one of the most common is simply breaking a weak bond by adding heat or light.

Show the mechanism, with curved arrows and products, for breaking the weak O- O bond in these cases.
Which of the two molecules would undergo bond cleavage most easily?