- You understand that carbon with an unpaired electron is a radical, one of four major reactive intermediates in organic chemistry.
- You understand that radicals are formed by homolytic bond cleavage, and you can describe the difference between homolytic and heterolytic bond cleavage.
- You know the four classes of reaction that radicals undergo: atom abstraction, addition to multiple bonds, rearrangement, and recombination.
- You can rank the relative stability of tertiary, secondary, primary, and methyl radicals based on relative C-H BDEs, and can use these principles to estimate radical stability if given the respective C-H BDE.
Visualization: Hyperconjugation in the tert-butyl radical
- You can draw each step for initiation and propagation in the conversion of methane and chlorine to chloromethane, and can draw at least one termination step in this mechanism.
Visualization: Chlorination of Methane
- You can apply this mechanism to the radical halogenation of any C-H bond in any alkane.
- You can estimate ΔH° for each propagation step in an alkane halogenation and predict whether the overall conversion is feasible (exothermic) or not (endothermic).
- You can relate halogen reactivity to activation barriers for different halogenation reactions, and use that to qualitatively predict selectivity.
- You can use principles of symmetry and potential selectivity to state whether a particular halogenation is synthetically useful or not.
- You understand the role of resonance/Π delocalization in stabilizing allylic and benzylic radicals, weakening allylic and benzylic C-H bonds and promoting allylic and benzylic radical reactions such as bromination.
See a fun YouTube video illustrating C-H bind strength variation in photochemical bromination of alkylbenzenes.
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