Learning Objective: To learn how to predict the stability of a hydrocarbon to form a free radical using the dissociation energy value of the C-H bond.
Skill Level - Intermediate
Prerequisites:
Chapter: Reactive Intermediates
Sub-topic: Free Radicals
Author's Note: In the previous section, we learned various factors contributing to free radical stability. In this section, we will learn how to predict whether a given hydrocarbon can form a stable free radical from the C-H bond's dissociation (D) energy values. Also, we will see which of the four stabilizing factors contributes to its low D value or which structural feature contributes to its instability.
Comparing Free Radical Stability using Dissociation Energy Value
Stability due to different inherent factors like inductive, resonance and electronegativity in a carbon-free radical can be compared and ordered from the Dissociation energies (D values) of the R-H bonds. The higher the D value, the less stable the radical.
D values of some R-H bonds are shown in the table
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Note- Most molecules are stabilized by a combination of factors where one factor is predominant than the others, as shown in the table.
