Aim: Preliminary investigations and qualitative analysis of solid organic compounds with
functional groups detection
I. Preliminary Investigation:
1. Colour:
2. State (Solid or Liquid)
3. Odour (Characteristic smell)
4. Solubility
Solvent Cold Hot
Water
5 % NaOH
5 % HCl
5 % NaHCO3
Ethanol
Si. Experiment Observation Inference
No.
5 Test for Unsaturation/ Saturation Isolated
a) Sample solution + KMnO4 solution Solution decolorizes
b) Sample + Br2 solution Solution decolorizes
present
6 Ignition test Burns with a sooty Aromatic
flame
7 Litmus Test
a) With blue litmus Blue turns red Acidic
b) with red litmus Red turns blue Basic
II. Detection of extra elements: Performed with Lassigne’s Filtrate (L.F.)
1
Preparation of Lassignes Filtrate (L.F.):
Place a piece of sodium metal (about a quarter size of a pea) in an ignition tube (a soft
glass test tube) and a small amount of organic sample. Hold the tube by a test tube holder
and heat it gently and carefully on the Bunsen flame when solid melts. The tube has to be
shaken carefully in the flame to avoid excessive local heating and to ensure mixing of the
sample with the melted sodium. Then heat slowly then prolong heating to red hot
condition. Then immediately immerse the tube in 5 –10 mL distilled water taken in a 100
mL beaker. Boil the solution carefully and gently for five minutes, filter in cold condition
and collect the filtrate. This solution is called Sodium Fusion Extract or Lassigne’s
filtrate. The filtrate should be water-clear and alkaline. If it is dark colored the whole
fusion operation is to be repeated.
Si. Experiment Observation Inference
No.
1 Prussian blue test for nitrogen: Prussian blue Colouration N present
L.F. + FeSO4 solution + H2SO4
2 Test for S: S- present
a) Na-Nitroprusside Test: Purple colour solution
L.F. + Na-nitroprusside solution
b) Pb-acetate test: Black ppt. Occurs
L.F. + CH3COOH + Pb-acetate
solution
3 Test for Halogens: A curdy white ppt. soluble Cl present
in NH3 solution
Pale yellow ppt. partially Br present
L.F. + dil. HNO3 + AgNO3 solution
soluble in NH3 solution
Yellow ppt. insoluble in I present
NH3 solution
4 Test for nitrogen and Sulphur Blood red colour Both N and S
present together: present
L.F. + dil. HCl + FeCl3 solution
2
III. Detection of Functional group
Note: If the elements N and S are not detected in the Lassignes’s test, test for functional
groups containing N and S should not be performed
Si. Experiment Observation Inference
No.
1 Test for carboxylic group:
a) NaHCO3 test: Effervescence of -COOH
sample + NaHCO3 solution colourless and odourless present
gas
b) Ester formation test: Fruity smell -COOH
sample + ethanol + heat + conc. H2SO4 present
2 Test for phenolic group (Ar-OH) Ar-OH
a) Neutral FeCl3 test: Dark Colouration
present
Sample solution + Neutral FeCl3
b) Libermann’s nitroso test: Blue coloration which
Has to be performed in dry test tube become red on dilution
c) Phthalein Test:
Dark colouration
3 Test for alcoholic (R-OH) group: Red colour appears R-OH
Ceric ammonium nitrate test: present
Sample Solution + Ceric ammonium
nitrate solution
4 Test for carbonyl group: Yellow/orange ppt. Carbonyl
a) Brady’s Test: occurs group
present
3
b) 0.1 gm of substance + 1mL freshly Wine red colour R-CO-CH3
prepared Sodium nitro prusside solution +
present
few drops of dilute NaOH solution
Note: If Brady’s test fails, the test for aldehyde group should not be performed.
5 Test for aldehyde (-CHO) group: -CHO
a) Fehling Test: Red ppt. occurs
present
Sample + Fehling solution
b) Tollen’s Test: Formation of silver
sample + Ammonical AgNO3 solution+ mirror
heat
Note: If Brady’s test shows positive observation but the test for aldehyde group fails
indicates that sample contains ketone.
6 Test for –NH2 group:
a) Carbylamines test: Albuminous smell R-NH2
Sample + KOH (alcholic) + CHCl3 + heat present
b) Azodye test: Red dye appears Ar-NH2
present
7 Test for –NO2 group
a) in the presence of amine (-NH2) group: A white precipitate -NO2
turning grew on present
Mulliken Barker Test: standing indicates nitro
Sample solution + ammonium chloride + group. (Mostly you see
Zn-dust and boil the mixture. Filter the the grey
solution to attest tube containing Tollen’s precipitates as a result of
reagent. excess of the filtrate)
b) In absence of NH2:
To a small amount of substance + add 3-4
ml dil. HCl + a pinch of Zn dust ----->
boil the mixture for 5min and then cool
the reaction mixture and filtered.
Filtrate divided into two parts
Part 1: perform carbylamines test
Part 2 : Perform azo dye Test
4
8 Test for amide (-CONH2) group Smell of NH3 occurs -CONH2
present
9 Test for urea: Purple or deep blue Urea
Heat small amount of the compound in a colour present
dry test tube. The compounds melt,
ammonia is evolved and gradually the
liquid solidifies due to the formation of
biuret. Now dissolve the residue in dilute
solution of NaOH and add 1, 2-drops of
dilute CuSO4 solution.
10 Test for Thiourea: Black colour solution Thiourea
Small amount of substance + aq NaOH present
---------> Cool the solution and add few
drops of aqueous Lead Acetate
Results:
The given sample bears functional group………………………………………
