Carboxylic Acids & Their Derivatives
(COMEDK – Chemistry – Advanced Year – Study Notes)
1. Simple Explanation
| Term | What it means |
|---|---|
| Carboxylic Acid | A compound that contains the functional group –COOH (the carboxyl group). |
| Derivatives | Compounds that are chemically related to carboxylic acids but have one or more atoms of the carboxyl group replaced. |
Carboxylic acids are the simplest oxygen‑containing acids. They are weak acids (pKa 4–5) and are soluble in water. Their derivatives—acid chlorides, anhydrides, esters, and amides—are produced by replacing the hydroxyl (OH) part of the carboxyl group with halogen, oxygen, or nitrogen atoms. These derivatives are extremely important in organic synthesis, pharmaceuticals, and industrial chemistry.
2. Key Points
2.1 Carboxylic Acids
| Feature | Details |
|---|---|
| General Formula | R–COOH (R = alkyl, aryl, or alkoxy) |
| Acidic Properties | The lone pair on O and the resonance stabilize the conjugate base (R–COO⁻). |
| Physical Properties | 1) Boiling point higher than alcohols of similar molar mass. 2) Strong dipole–dipole interactions (C–O and O–H). 3) Often dissolve in organic solvents and water. |
| Common Examples | Acetic acid (CH₃COOH), Benzoic acid (C₆H₅COOH), Formic acid (HCOOH). |
| Naming Rules | 1) Replace “–ic acid” with “–ic” for the acid. 2) Replace “–ic acid” with “–yl” for the derivative. |
| Acidic Reaction | R–COOH + H₂O ⇌ R–COO⁻ + H₃O⁺ (pKa ≈ 4–5). |
2.2 Derivatives
| Derivative | General Formula | Key Features | Typical Reaction |
|---|---|---|---|
| Acid Chloride (Acyl Chloride) | R–COCl | Very reactive, used as acylating reagent. | R–COCl + H₂O → R–COOH + HCl (hydrolysis). |
| Acid Anhydride | (R–CO)₂O | Formed by dehydration of two acids. | (R–CO)₂O + H₂O → 2 R–COOH. |
| Ester | R–COOR' | Sweet smell, used in fragrances & fuels. | R–COOH + R'OH ⇌ R–COOR' + H₂O (Fischer esterification). |
| Amide | R–CONR'₂ | Strong C–N bond, low reactivity. | R–COOH + R'NH₂ → R–CONR'₂ + H₂O (amide formation). |
| Acid Halides (other than Cl) | R–COX (X = Br, I) | Similar to acid chloride but less reactive. | Hydrolysis → R–COOH. |
| Carboxylate Salt | R–COO⁻Na⁺ | Salt of acid, high solubility in water. | R–COOH + NaOH → R–COONa + H₂O. |
2.3 Common Reactions of Derivatives
| Reaction | General Formula | Notes |
|---|---|---|
| Hydrolysis (acidic or basic) | R–COOR' + H₂O → R– |