Fundamentals of Organic ChemistryChemistryAldehydes and Ketones
In general, ketones are more reactive towards nucleophiles than esters. What is the primary reason for this difference in reactivity?
Options
- AThe -protons of a ketone are more acidic than those of an ester.
- BThe alkyl group in a ketone is an electron-donating group due to hyperconjugation.
- CAlkoxy ( -OR ) groups are sterically larger than the corresponding alkyl groups.
- DAlkoxy ( -OR ) groups are stronger electron donors than alkyl groups via resonance.
Correct answer
D. Alkoxy ( -OR ) groups are stronger electron donors than alkyl groups via resonance.
Step-by-step solution
The reactivity of carbonyl compounds towards nucleophiles depends on the magnitude of the partial positive charge (electrophilicity) on the carbonyl carbon. In esters ( R-CO-OR' ), the alkoxy group ( -OR' ) donates electron density to the carbonyl carbon through resonance (+R effect) involving the lone pairs on the oxygen atom. This resonance effect significantly decreases the electrophilicity of the carbonyl carbon. In ketones ( R-CO-R' ), the alkyl groups donate electron density only through weaker inductive (+I)