Properties of carboxylic acids

Full Notes

Solubility of Carboxylic Acids in Water

Carboxylic acids contain polar –OH and C=O groups capable of forming hydrogen bonds with water.

This makes low-mass carboxylic acids with small R groups or carbon chains (e.g. methanoic and ethanoic acid) very soluble.

As chain length increases, the non-polar hydrocarbon portion reduces solubility.

Reactions with Metals and Bases

Carboxylic acids behave as weak acids (H⁺ ion donors) and react with typical bases to form salts.

With Reactive Metals

Explanation: Metal displaces hydrogen from the –COOH group, producing hydrogen gas and a carboxylate salt.

Example Reaction with Zinc

2CH₃COOH + Zn → (CH₃COO)₂Zn + H₂(g)

With Alkalis

Explanation: OH⁻ accepts the H⁺ from the –COOH group, forming a salt and water.

Example Reaction with Sodium Hydroxide

CH₃COOH + NaOH → CH₃COONa + H₂O

With Metal Oxides

Salt and water form.

Example Reaction with Copper(II) Oxide

2CH₃COOH + CuO → (CH₃COO)₂Cu + H₂O

With Metal Carbonates

Explanation: Typical acid–carbonate reaction producing carbon dioxide, water, and a salt.

Example Reaction with Sodium Carbonate

2CH₃COOH + Na₂CO₃ → 2CH₃COONa + CO₂ + H₂O

Summary

• Carboxylic acids are soluble in water due to hydrogen bonding, but solubility decreases with longer chains.
• They are weak acids and form salts by donating a proton from the –COOH group.
• They react with metals to give salts and hydrogen.
• They react with alkalis and metal oxides to give salts and water.
• They react with carbonates to give salts, water and carbon dioxide.