AIM: To carry out the Qualitative analysis of second group compounds
Amides
Sample:Thiourea
I. Preliminary Examination
| Experiment | Observation | Inference |
|---|---|---|
| a)Physical State |
Solid | Acids, Suga, Amides, Ailides |
| b) Colour | Colourless |
Acids, Suga, Amides, Ailides |
| c) Odour |
No characteristics odour |
Acids, Suga, Amides, Ailides |
| Ignition Test: Ignite a small quantity of the substance taken on nickle spatula |
Burns with non-smoky flame with the snell of rotten egg(H2S) |
Aliphatic Compound |
| Test for Unsaturation Substance + water +0.5ml of sodium carbonate solution + KMnO4 solution drop by drop shake. |
No Decolourisitation of KMnO4 |
saturated Comounds |
Detection
of Special Elements (Nitrogen, Sulphur & Halogens) by Lassaigne's
Test Preparations of sodium fusion extract (SFE)
Place a small piece of freshly cut dry sodium in a dry sodium fusion tube and melted to a shining globule. Introduce 2drops of 0.1g of the given substance. Heat the tube gently in the beginning and then strongly to red heat for 1-2minutes. Then plunge the red-hot tube into about 10ml distilled water taken in a mortar. Grind the mixture and filter. The colorless filtrate is called stock solution.
Test for nitrogen, sulphur and halogens are carried out with the stock solution:| Experiment | Observation | Inference |
|---|---|---|
| Test for Nitrogen: 2ml of stock solution+few crystals (0.1-0.2g) of ferrous sulphate, boil gently, cool, acidify with dill H2SO4 till the solution is clear, add neutral FeCl3 |
Blue Or Green Colour |
Nitrogen Present |
| Test for Sulphur: a)2ml of stock solution+ 2-3 drops of freshly prepared sodium nitropusside solution+ 1drop of dil NaOH b) 2ml of stock solution +2-3 drops of lead acetate solution+ 1drop of acetic acid |
purple colour brown/Black colour |
Sulphur Present |
| Test for Halogens: (Cl, Br&I) 1ml of stock solution +1ml of dil HNO3 boil well, Cool and then add 10% AgNO3 solution |
No Precipitate |
Halogen Absent |
Solubility grouping:
| Water | Ether | 5% NaOH |
5% NaHCO3 |
Dil. HCL |
DIl H₂SO₄ | Group |
|---|---|---|---|---|---|---|
| + | - | - | - | - | - | II |
Report: Given sample contains special elements such as Nitrogen and sulfur and soluble in water belongs to Group II, the given may be amides not carbohydrates.
Qualitative Tests for Amides:
| Experiment | Observation | Infernce |
|---|---|---|
| 1. Boil 0.3g of the substance+3ml of 10% NaOH smell Hold a moist red litmus paper or glass rod dipped in Conc. HCl Near the mounth of test tube |
Smell of ammonia Red litmus turns to blue/ dense white fumes of Nh4cl near the glass rod |
Amide Present |
| 2.Boil a small quantity of the substance with 3ml of 1:1 HCl |
Acetic acid evolved |
Amide present |
| 2.Ciuret test: Boil 0.3g of the substance in dry test tube+Dissolve in 3ml of dil NaOH. Add drop wise a very dil CuSO4 |
No purple/ Violet color | Urea is Absent |
| Test for Thiourea: 4. Boil 0.3g of the substance in 3ml of NaOH. Heat,add solution of lead acetate |
Brown/Black colour |
Thiourea present |
| 5. Boil 0.3g of the substance and NaOH in dry test tube+Dissolve in H2O. Add solution of aqueous FeCl3 solution |
Blood red Colour |
Thiourea present |
Report: The given sample is solid, aliphatic presence of special elements nitrogen and sulfur, soluble in water, belongs to Group II, Negative for Biuret test, positive for lead acetate so the given sample is amide, since it contains both nitrogen and sulfur may be Thiourea
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