Acetone, , becomes significantly more reactive after deprotonation at one of its…
CHEMISTRY · Multi-part · AP · Chemistry · Compound Structure and Properties · Compound Structure and Properties
Problem
Acetone, (CH3)2C=O, becomes significantly more reactive after deprotonation at one of its methyl groups to form the enolate anion CH3COCH2−.
The enolate anion is often depicted with a negative charge on carbon, but experimental studies reveal substantial electron density on oxygen as well.
(a) Draw the starting Lewis structure for the acetone enolate anion in which the negative charge is placed on the α-carbon.
(b) Using curved-arrow notation, generate every additional resonance contributor obtainable by delocalizing the lone pair or π electrons. Draw each contributor clearly.
(c) For each resonance contributor, calculate and record the formal charge on every atom.
Then rank the contributors in order of expected relative importance to the resonance hybrid, providing two distinct reasons for the position of each structure in your ranking.
(d) Combine the information from parts (a)–(c) to draw a resonance hybrid that depicts partial bond orders and partial charges. Explain how this hybrid accounts for the fact that the enolate oxygen is far more basic than the corresponding carbon.