Radical Selectivity

Not all radicals are born equal! Some of them are going to make pretty smart decisions from an energy perspective, while others are a little on the crazy side. Let’s turn to some potential role models for guidance on this topic. 

Drinking Responsibly vs. Getting Destroyed:

Selectivity is defined as the ability to only halogenate the carbons with most stable radical intermediates.

Example: Predict the product of the following Radical Halogenation. Would the following reaction be synthetically useful? (Yielding only one product). 

1m

Example: Predict the product of the following Radical Halogenation. Would the following reaction be synthetically useful? (Yielding only one product). 

2m

Example: Predict the product of the following Radical Halogenation. Would the following reaction be synthetically useful? (Yielding only one product). 

2m

Example: Predict the product of the following Radical Halogenation. Would the following reaction be synthetically useful? (Yielding only one product). 

1m

Hammond’s Explanation:

Early transition states could care less what they look like, whereas late transition states have to be much more careful about the arrangements they take. 

Concept: Using the Hammond Postulate to describe radical bromination. 

6m