Organic Chemistry: Concepts and Applications - Headley Allan D. 2020

Free Radical Substitution Reactions Involving Alkanes
14.6 Free Radical Inhibitors

For reactions that proceed via a free radical mechanism, if a stable-free radical were introduced, the reaction will stop owing to the coupling of the introduced stable radical with the radical intermediates of the reaction. Stable radicals if used in this sense are called inhibitors or antioxidants, and they are frequently used in the food industry as preservatives. Butylated hydroxytoluene (BHT) is one such example.

Problem 14.9

Using single-barbed arrows to indicate electron movements, give two resonance structures of the radical of butylated hydroxytolune (BHT).

Another radical that is of biological importance is the radical derived from Vitamin E, also known as α-tocopherol radical, its structure is shown below. Due to the stability of this α-tocopherol radical and its ability to act as a radical scavenger, it plays an important role in protecting the organism against oxidative damage.