Organic Chemistry MCAT Practice Exam

The kinetic enolate forms faster and is less sterically hindered primarily due to its formation from a less stable intermediate that is favored by lower temperatures. Kinetic control refers to the situation where the reaction conditions favor the formation of a product that is formed more quickly, even if that product is not the most stable form of the enolate.

In the case of enolate formation, the kinetic enolate is generated from a less hindered α-hydrogen being abstracted by a strong base, leading to the formation of a double bond at the less substituted position of the carbonyl compound. This rapid abstraction results in a more accessible transition state, which leads to the formation of the kinetic enolate rather swiftly compared to the thermodynamic enolate, which has to rearrange and stabilize at a more substituted position, favoring stability over speed.

Therefore, the kinetic enolate is characterized by being less sterically hindered and can be achieved by using sterically unhindered bases under conditions that promptly lead to product formation. This contrasts with the thermodynamic enolate, which, while more stable, takes longer to form due to the higher energy barrier associated with its formation from a more substituted position.