Question

E. Why is the BHT radical unreactive? It is sterically hindered.

Short answer

Answer: The BHT radical is unreactive due to the steric hindrance caused by the large tert-butyl groups surrounding the key reactive site. These groups make it difficult for other molecules to approach and interact with the unpaired electron, ultimately limiting the reactivity of the BHT radical.

Step-by-step solution

Understand sterically hindered molecules

Steric hindrance occurs when large groups around a central atom limit the accessibility or reactivity of that atom. This often results in reduced reactivity, as other molecules struggle to reach and react with the hindered site.

Observe the BHT radical structure

BHT, or butylated hydroxytoluene, has the following chemical structure: C(CH_3)_3 - C_6H_2(CH_3)_2 - OH The structure includes three bulky tert-butyl groups (C(CH_3)_3), which are well known for causing steric hindrance.

Analyze the hindered site

In a BHT radical, one of the hydrogen atoms connected to the hydroxyl group (OH) is replaced by an unpaired electron, generating the radical. This electron, needed for a chemical reaction, is surrounded by the large tert-butyl groups. As a result, other reactants have difficulty approaching and interacting with the electron, causing a decrease in reactivity.

Conclude

In summary, the BHT radical is unreactive due to the steric hindrance caused by the large tert-butyl groups surrounding the key reactive site. These groups make it difficult for other molecules to approach and interact with the unpaired electron, ultimately limiting the reactivity of the BHT radical.