CHEMCA
EXAM MASTER REVIEW SHEET
Qualitative Analysis: Functional Group Tests
1. Unsaturation & Halogens
Reagent: $Br_2 / CCl_4$ (Orange-brown).
Positive: Decolourization (Alkenes & Alkynes).
Heat compound on a clean copper wire in Bunsen flame.
Positive: Green/Bluish-green flame.
2. Alcohols & Phenols
| Functional Group | Test Name | Observation |
|---|---|---|
| Alcohols ($ROH$) | Sodium Metal Test | Brisk Effervescence ($H_2$ gas evolution). |
| Alcohols ($1^\circ, 2^\circ, 3^\circ$) | Lucas Test (Anhyd. $ZnCl_2 + HCl$) | Turbidity: Immediate ($3^\circ$), 5 min ($2^\circ$), None ($1^\circ$). |
| Phenols ($ArOH$) | Neutral $FeCl_3$ | Violet / Purple Coloration. |
| Phenols ($ArOH$) | Bromine Water | White Precipitate (2,4,6-tribromophenol). |
3. Aldehydes & Ketones
Reaction with Brady's Reagent.
Observation: Yellow / Orange / Red Precipitate.
Tests for $CH_3-CO-$ or $CH_3-CH(OH)-$ groups.
Observation: Yellow Crystalline Ppt ($CHI_3$).
Distinguishing Aldehydes from Ketones
Tollen's Test: Ammoniacal $AgNO_3$.
Result: Silver Mirror on inner wall of tube. (Aldehydes only).
Fehling's Test: Fehling A + B solutions.
Result: Reddish-brown ppt ($Cu_2O$). (Aliphatic Aldehydes only).
4. Acids & Nitrogen Groups
Carboxylic Acids ($R-COOH$)
Reagent: $NaHCO_3$ Solution.
• Observation: Brisk effervescence of $CO_2$ gas.
• Ester Test: Heat with alcohol + $H_2SO_4 \rightarrow$ Fruity Smell.
Amines ($R-NH_2$)
• Carbylamine Test ($1^\circ$ only): Heat with $CHCl_3 + alc. KOH \rightarrow$ Foul smell of Isocyanide.
• Dye Test (Aromatic $1^\circ$): $NaNO_2/HCl$ then 2-naphthol $\rightarrow$ Scarlet Red Dye.
5. Master Summary of Colour Observations
| Reagent | Functional Group Identified | Key Visual Result |
|---|---|---|
| Schiff's Reagent | Aldehydes | Pink / Magenta |
| Ceric Ammonium Nitrate | Alcohols | Pink / Red |
| Liebermann's Nitroso | Phenols | Blue (with NaOH) |
| Ninhydrin | Amino Acids | Intense Purple / Blue |
| Biuret Reagent | Proteins (Peptide bond) | Violet |
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