CHEM267 Chapter Notes - Chapter 20: Nucleophilic Addition, Grignard Reaction, Steric Effects
Document Summary
The carbon of a carbonyl group is especially electrophilic due to both resonance and inductive effects (both resultling in a positive charge on c); making it susceptible to nucleophilic attack. Rule: nucleophilic attack occurs at an angle of 107 to the plane of the carbonyl group. Rule: aldehydes are more reactive than ketones to nucleophilic attack. When an aldehyde or ketone is treated with water, the carbonyl group is converted to a hydrate. Equilibrium favours the carbonyl group rather than the hydrate (except for simple aldehydes) Reaction is relatively slow under neutral conditions, but enhanced in the presence of acid or base: base catalyzed = nucleophilic attack on c (from base), then protonation of o. Negatively charged intermediate is formed (-ve charge on o: acid catalyzed = protonation of o (from acid), nucleophilic attack on c, deprotonation. Positively charged intermediate is formed (+ve charge on o) When an alcohol attacks an aldehyde or ketone, an acetal is formed.