Chapter 6 · Class 11-12 & JEE/NEET
Carboxylic Acids & Derivatives
61 topics in 12 parts
Key ideas
Diagnostic Comparison & Property Matrix
| Parameter / Feature | Standard State / Condition A | Altered State / Condition B |
|---|---|---|
| Driving Force | Thermodynamic control (more stable product) | Kinetic control (lower activation barrier) |
| Solvent Dependency | Polar protic solvent stabilizes charge separation | Polar aprotic solvent accelerates bare nucleophilicity |
| Temperature Influence | High temperatures favor elimination / endothermic | Mild temperatures favor addition / exothermic |
| Common Pitfall | Overlooking rearrangement or stereochemical inversion | Neglecting boundary limits or stoichiometric coefficients |
Conceptual Foundation & Core Theory
The oxidation of alcohols is one of the most critical functional group transformations in organic chemistry. It involves the removal of hydrogen atoms from both the oxygen atom (O—H) and the carbon atom bearing the hydroxyl group (the α-hydrogen, C—H), thereby forming a carbon-oxygen double bond (C=O).
Reagents & Mechanism with Chromic Acid: Chromic acid (H₂CrO₄, often generated in situ from CrO₃ + H₂SO₄ in aqueous acetone, known as the Jones Reagent) operates by first condensing with the alcohol to form a chromate ester intermediate: R-CH₂-O-CrO₃H. Water then abstracts an α-hydrogen in an E2-like elimination, reducing toxic Chromium(VI) (orange) to Chromium(III) (green).
Behavior Across Alcohol Classes:
• Primary (1°) Alcohols: Readily oxidized to aldehydes. However, in aqueous media, aldehydes quickly form germinal diols (hydrates, RCH(OH)₂), which are immediately oxidized further into carboxylic acids (RCOOH). To stop oxidation at the aldehyde stage, anhydrous reagents such as PCC (Pyridinium Chlorochromate) or Swern oxidation must be employed.
• Secondary (2°) Alcohols: Smoothly oxidized to ketones (R₂C=O). Ketones do not possess an α-hydrogen on the carbonyl carbon and cannot form hydrates easily, so they are resistant to further oxidation under standard conditions.
• Tertiary (3°) Alcohols: Lack an α-hydrogen entirely. Consequently, 3° alcohols do not undergo oxidation with chromic acid or neutral KMnO₄ at room temperature. Under severe heating with acidic KMnO₄, they first dehydrate to an alkene, followed by oxidative cleavage of the double bond.
Standard Reaction & Reagent Conditions
// Oxidation Reactions of Alcohols & Reagent Selectivity
1. Primary Alcohols (1°):
R-CH2-OH + H2CrO4 (Jones) / KMnO4(aq) ──> R-COOH (Carboxylic Acid)
R-CH2-OH + PCC / CH2Cl2 (Anhydrous) ──> R-CHO (Aldehyde stops here!)
2. Secondary Alcohols (2°):
R-CH(OH)-R' + H2CrO4 / KMnO4 / PCC ──> R-C(=O)-R' (Ketone)
3. Tertiary Alcohols (3°):
R3C-OH + Jones Reagent / Neutral KMnO4 ──> NO REACTION (Resistant)
4. Color Change Test (Alcohol Breathalyzer Principle):
CrO3 / H2SO4 (Orange, Cr⁺⁶) ──[ Alcohol ]──> Cr2(SO4)3 (Green, Cr⁺³)Oxidizing Reagents & Functional Group Selectivity Matrix
| Oxidizing Reagent | Condition / Solvent | Primary (1°) Alcohol Product | Secondary (2°) Alcohol Product | Tertiary (3°) Alcohol |
|---|---|---|---|---|
| Jones Reagent (CrO3 / H2SO4) | Aqueous Acetone | Carboxylic Acid (RCOOH) | Ketone (RCOR) | No Reaction |
| Potassium Permanganate (KMnO4) | Alkaline / Acidic heat | Carboxylic Acid (RCOOH) | Ketone (RCOR) | Cleaves after dehydration |
| PCC (Pyridinium Chlorochromate) | Anhydrous CH2Cl2 | Aldehyde (RCHO) [Selective!] | Ketone (RCOR) | No Reaction |
| Cu at 573 K (Dehydrogenation) | Gas phase / 300°C | Aldehyde (RCHO) | Ketone (RCOR) | Alkene (Dehydration!) |
Step-by-Step Solved Problem (JEE Advanced Standard)
Problem: Three isomeric alcohols with molecular formula C₄H₁₀O (Compounds X, Y, and Z) are subjected to oxidation with acidified potassium dichromate (K₂Cr₂O₇). Compound X produces a carboxylic acid C₄H₈O₂. Compound Y produces a ketone C₄H₈O. Compound Z does not react. Identify X, Y, and Z.
Checkpoint
1. Which reagent converts propan-1-ol into propanal without further oxidation to propanoic acid?
All 61 topics in Carboxylic Acids & Derivatives
Nomenclature & Common Name
- Carboxylic Acids
- Carboxylate Salts
- Dicarboxylic Acids
- Acyl Chlorides
- Carboxylic Anhydrides
- Esters
- Amides
- Nitriles
Preparation of Carboxylic Acids
- From Alkyl Halides
- Oxidation of Alcohols & Aldehydes
- Oxidation of Ketones
- Oxidation of Alkylbenzenes
- Hydrolysis of Nitriles
- Carboxylation of Organometallic Compounds
- Malonic Ester Synthesis
- Arndt-Eistert Synthesis
Acidity & Physical Properties
- Physical Properties
- Acidity & pKa
- Inductive Effect
- Resonance & Substituent Effects
- Reaction with Bicarbonate
- Vinegar Composition
Nucleophilic Acyl Substitution
- Addition-Elimination Mechanism
- Relative Reactivity of Acyl Compounds
- Interconversion of Acid Derivatives
Acyl Chlorides
- Synthesis of Acyl Chlorides
- Reactions of Acyl Chlorides
- Reduction to Aldehydes
Carboxylic Acid Anhydrides
- Synthesis of Carboxylic Acid Anhydrides
- Reactions of Carboxylic Acid Anhydrides
- Cyclic Anhydrides & Imides
Esters
- Esterification
- Transesterification
- Acidic Hydrolysis
- Saponification
- Reduction of Esters
- Lactones
- Baeyer-Villiger Oxidation
Amides & Nitriles
- Synthesis of Amides
- Amides from Acyl Chlorides
- Amides from Carboxylic Acids & Ammonium Carboxylates
- Amides from Carboxylic Anhydrides
- Amides from Esters
- Hydrolysis of Amides
- Reactions of Amides
- Lactams
- Synthesis of Nitriles
- Nitriles from Dehydration of Amides
- Hydrolysis of Nitriles
Carboxylic Acid Reactions
- Salt Formation
- Reduction of Carboxylic Acids
- Reduction of Acyl Derivatives
- Hell-Volhard-Zelinsky Reaction
- Pyrolysis & Dehydration
- Multi-Step Synthesis
Decarboxylation of Carboxylic Acids
- Soda-Lime Decarboxylation
- Thermal Decarboxylation of β-Keto & Dicarboxylic Acids
- Decarboxylation of Carboxyl Radicals
Chemical Tests for Acyl Compounds
- Carboxyl Group Tests
- Distinguishing Phenols & Carboxylic Acids
Derivatives of Carbonic Acid
- Urea & Derivatives