Carboxylic Acid and Derivatives
High-Yield Summary
- Carboxylic acid: carbonyl + hydroxyl on the same terminal carbon (COOH) — the highest-priority MCAT functional group, most oxidized. Suffix -oic acid.
- Ester: acid's -OH replaced by -OR (alkoxy). Suffix -oate, named alkyl-group-first then acid-derived-part-oate (propyl ethanoate).
- Amide: acid's -OH replaced by -NR₂ (amino). Suffix -amide; N-substituents cited with N- prefix (N,N-dimethylethanamide).
- Anhydride: two carboxylic acids dehydrated together. Suffix -anhydride; symmetrical anhydrides use one acid name, mixed anhydrides list both alphabetically.
- Full priority order: carboxylic acids > anhydrides > esters > amides > aldehydes > ketones > alcohols > alkenes > alkynes > alkanes. Highest-ranked group present takes the suffix; everything else becomes a prefix.
Functional Group Suffix / Prefix Table
| Functional Group | Suffix / Prefix (when not highest priority) |
|---|---|
| Carboxylic acid | -oic acid / carboxy- |
| Anhydride | -anhydride / — |
| Ester | -oate / alkoxycarbonyl- |
| Amide | -amide / carbamoyl- or amido- |
| Aldehyde | -al / oxo- |
| Ketone | -one / oxo- or keto- |
| Alcohol | -ol / hydroxy- |
| Alkene | -ene / alkenyl- |
| Alkyne | -yne / alkynyl- |
| Alkane | -ane / alkyl- |
Key Terms
- Carboxylic acid
- COOH — carbonyl + hydroxyl on the same carbon; acidic due to resonance-stabilized conjugate base; both H-bond donor and acceptor.
- Esterification
- Acid-catalyzed reaction between a carboxylic acid and an alcohol that forms an ester.
- Amide (peptide bond)
- Formed by replacing an acid's -OH with -NR₂; the bond holding proteins together; highly polar, strong H-bonding, less acidic than the parent acid.
- Symmetrical vs. mixed anhydride
- Symmetrical: both sides from the same acid (ethanoic anhydride). Mixed: sides from two different acids, named alphabetically (ethanoic propanoic anhydride).
Common MCAT Trap
- Carboxylic acid is always the highest priority when present — it takes the suffix and forces every other functional group (even another carbonyl-based one) into a prefix.
- Ester naming order is easy to reverse: alkyl group (from the alcohol) comes first, then the acid-derived -oate part — propyl ethanoate, not ethanoate propyl.
- Mixed anhydrides are alphabetized by acid name, not by any other rule — ethanoic before propanoic.
Quick Recall
Why is a carboxylic acid the highest-priority functional group on the MCAT?
How is an ester named, using propyl ethanoate as the example?
What's the prefix used for an amide when a higher-priority group is present?
State the full functional-group priority order from this chapter.