Fundamentals of Organic ChemistryChemistryCarboxylic Acid Derivatives
Which of the following best explains why the reaction of a Grignard reagent with a carboxylic acid does not yield a secondary alcohol?
Options
- AGrignard reagents exclusively react with aldehydes, ketones, esters, and epoxides.
- BThe carboxylic acid is too sterically hindered for the Grignard reagent to attack.
- CThe Grignard reagent acts as a strong base, so an acid-base reaction occurs preferentially.
- DThe carboxylic acid is not electrophilic enough to undergo nucleophilic addition.
Correct answer
C. The Grignard reagent acts as a strong base, so an acid-base reaction occurs preferentially.
Step-by-step solution
Grignard reagents ( RMgX ) are not only strong nucleophiles but also very strong bases. Carboxylic acids ( RCOOH ) contain a highly acidic proton. When a Grignard reagent is mixed with a carboxylic acid, an acid-base reaction occurs much faster than nucleophilic addition to the carbonyl carbon. The Grignard reagent deprotonates the carboxylic acid to form an alkane ( RH ) and a carboxylate salt ( RCOO⁻ , ⁺MgX ). The resulting carboxylate anion is resonance stabilized and lacks sufficient electrophilicity to undergo