Activity Project: Identification of Functional Groups in Organic Compounds
Objective
To perform qualitative tests to identify various functional groups present in given organic compounds such as alcohols, aldehydes, ketones, carboxylic acids, phenols, and amines.
Materials Required
- Sample organic compounds (e.g., ethanol, acetone, benzaldehyde, acetic acid, phenol, aniline)
- Reagents: 2,4-Dinitrophenylhydrazine (2,4-DNP), Tollens’ reagent, Ferric chloride (FeCl₃), Bromine water, NaOH, Dilute H₂SO₄, NaHCO₃, etc.
- Test tubes and test tube stand
- Droppers/Pipettes
- Water bath
- Dilute acids and bases where required
Procedure (Sample Tests)
- Alcohol Test (Ethanol): Add sodium metal to ethanol — observe effervescence (H₂ evolution).
- Aldehyde Test (Benzaldehyde): Perform Tollens’ test; silver mirror forms if aldehyde present.
- Ketone Test (Acetone): Add 2,4-DNP; orange precipitate indicates ketone.
- Carboxylic Acid Test (Acetic Acid): React with NaHCO₃; effervescence due to CO₂ indicates acid.
- Phenol Test (Phenol): Add neutral FeCl₃; violet color indicates phenol.
- Amino Group Test (Aniline): Add nitrous acid; effervescence indicates primary amine.
Observation Table
| Compound | Functional Group | Test Performed | Observation | Inference |
|---|---|---|---|---|
| Ethanol | Alcohol (-OH) | Reaction with sodium metal | Effervescence observed | Presence of alcohol |
| Benzaldehyde | Aldehyde (-CHO) | Tollens’ test | Silver mirror formed | Presence of aldehyde |
| Acetone | Ketone (=CO) | 2,4-Dinitrophenylhydrazine test | Orange precipitate formed | Presence of ketone |
| Acetic acid | Carboxylic acid (-COOH) | Reaction with sodium bicarbonate | Effervescence due to CO₂ gas | Presence of carboxylic acid |
| Phenol | Phenolic -OH | Ferric chloride test | Violet coloration | Presence of phenol |
| Aniline | Amino (-NH₂) | Reaction with nitrous acid | Effervescence observed | Presence of primary amine |
Result
Each organic compound shows characteristic tests confirming its functional group, enabling qualitative identification.
Precautions
- Use clean and dry apparatus to avoid contamination.
- Handle reagents carefully; some are corrosive or toxic.
- Perform tests on small amounts to avoid wastage and hazards.
- Observe color changes and precipitates carefully for accurate interpretation.