AIM: To carry out the Qualitative analysis of seventh group compounds
(Nitro compounds)
Sample: Nitrobenzene
I. Preliminary Examination
| Experiment | Observation | Inference |
|---|---|---|
| a)Physical State |
Liquids | Aldehyde, ketones alcohols, Phenols, aniline |
| b) Colour | Yellow | Aldehyde, ketones alcohols, Phenols, aniline |
| c) Odour |
Charecteristic odour(bitter almond |
Esters, aldehyds, alcohols and anilines |
| Ignition Test: Ignite a small quantity of the substance taken on nickle spatula |
Burns with smoky flame |
Aromatic Compound |
| Test for Unsaturation Substance + water +0.5ml of sodium carbonate solution + KMnO4 solution drop by drop shake. |
No Decolourisitation of KMnO4 |
Unsaturated 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 |
No purple colour No brown/Black colour |
Sulphur Absent |
| 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 |
Soluability Grouping
| Water | Ether | 5% NaOH |
5% NaHCO₃ | Dil. HCL |
DIl H₂SO₄ | Group |
|---|---|---|---|---|---|---|
| - | - | - | - | - | - | VII |
Report: Given Sample contains nitrogen and doesn't belong to any group from-I-IV and insoluble in Cold Conc. H2SO4, hence belongs to group VII
Qualitative Tests for Nitro Compounds:
| Experiment | Observation | Inference |
|---|---|---|
| 1. Mulliken's and Barkers Test: Substance +2ml ethanol +1ml CaCl₂ + pinch of Zn dust or tin boil for 5min cool and filter into 2ml of Tollen's reagent. Heat on water bath if necessary |
Black ppt | Nitro Compound |
| 2. Acid Reduction Test: Substance +Conc HCl+pinch of Zn dust boil, cool perform dye test. Add 0.1 gm of NaNO2 soln cool at 0-5C and add β-Naphthol soln in NaOH |
Red color dye |
Nitro compound |
| 3. Janowsky reaction: Substance+5ml acetone+2ml of 5% NAOH shake well |
Faint yellow color |
Mono nitro compounds present |
| 44. Substance+Feso4 crystals+dilH2so4+ethanolic KOH. shake well |
Brown ppt |
Report: The given sample is yellow liquid , aromatic, unsaturated, given sample contains nitrogen and doesn't belongs to any group fromI-IV and insoluble in cold Conc H₂SO₄, hence belongs to groupVII. Positive for Acid reduction test, Janowsky test. May be mono nitro compound- Nitrobenzene.
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