fcg3 Flashcards
What happens when water reacts with a simple carbonyl group?
Water acts as a nucleophile, attacking the carbonyl carbon to form a geminal diol (hydrate) in a reversible reaction.
What are the two key steps in nucleophilic substitution of complex carbonyl groups?
Addition: The nucleophile attacks the carbonyl carbon, forming a tetrahedral intermediate.
Elimination: The carbonyl bond reforms, ejecting the leaving group.
Why is the leaving group important in nucleophilic substitution of carbonyls?
A good leaving group (e.g., Cl⁻, -OR, -NH₂) makes the reaction more favorable by stabilizing the transition state and facilitating elimination.
How do alcohols react with carbonyl compounds?
Alcohols attack carbonyl carbons in an acid-catalyzed reaction, leading to esterification (ester formation) or acetal formation depending on the conditions.
What is the mechanism of ester hydrolysis under acidic conditions?
Protonation of the ester to increase electrophilicity.
Nucleophilic attack by water, forming a tetrahedral intermediate.
Elimination of alcohol, yielding a carboxylic acid.
What is the difference between acid-catalyzed and base-catalyzed ester hydrolysis?
Acidic hydrolysis is reversible and forms a carboxylic acid + alcohol.
Base hydrolysis (saponification) is irreversible, forming a carboxylate anion + alcohol.
Why is base-catalyzed ester hydrolysis irreversible?
The carboxylate anion (R-COO⁻) formed is highly stable and does not readily convert back to the ester.
