Carboxylic acids have some very distinct physical properties because of their special carboxyl group (–COOH). Here are the main ones:
1. State and Odor
- The first few members (like formic acid and acetic acid) are colorless liquids with a strong, sharp, and unpleasant smell (vinegar-like).
- Higher acids (with more carbon atoms) are waxy solids with little or no odor.
2. Boiling Points
- Carboxylic acids have higher boiling points than alcohols, aldehydes, and ketones of similar molecular mass.
- This is because they can form strong hydrogen bonds with each other, often as dimers.
3. Solubility in Water
- Lower carboxylic acids (up to four carbons) dissolve readily in water due to hydrogen bonding with water molecules.
- Higher carboxylic acids are less soluble because the long hydrocarbon chain dominates and reduces polarity.
4. Density
- They are usually heavier than water (density greater than 1).
5. Taste
- Lower members (like acetic acid) have a sour taste.
In short: Carboxylic acids are generally sour, have high boiling points, are soluble in water if small, and form hydrogen bonds.