REVISION(Organic Chem)
TESTS OF DISTINCTION
1) ALIPHATIC AND AROMATIC HALIDES :-
Hydrolysis followed by reaction with AgNO3. Aliphatic halides give ppt. with
AgNO3 ,while aromatic halides do not.
RX +KOH 🡪 KX + AgNO3 🡪 Ag X (ppt.)
Q. Distinguish between i. Ethyl bromide & Bromobenzene
ii. Ethyl chloride & Vinyl chloride
2) PRIMARY, SECONDARY AND TERTIARY ALCOHOLS :-
Lucas reagent (Anhydrous ZnCl2 + Conc. HCl ) gives ppt. immediately with 30 alcohols,
after 5 min. with 20 alcohols & only on heating with 10 alcohols.
ROH + ZnCl2 + HCl 🡪 RCl (insoluble)+ H2O
Q. Distinguish between i. n-Propyl alcohol & isopropyl alcohol
ii. sec-butyl alcohol & tert-butyl alcohol
3) IODOFORM TEST :-
It is given by the compounds having CH3 (C=O)- grp and CH3CH(OH)- group. Formation
of yellow ppt of iodoform with NaOI (NaOH + I2).
RCOCH3 +NaOH +I2 🡪 CHI3 + RCOONa
(Yellow ppt)
RCH(OH)CH3 + NaOI --- NaOH +I2/heat 🡪 CHI3 + RCOONa
(Yellow ppt)
Q. Distinguish between i. n-Propyl alcohol & isopropyl alcohol
ii.Acetone & Diethylketone
iii. Acetophenone & Benzaldehyde
iv.Ethanol & Propanol
v. Propanal & Propanone
4) TEST FOR PHENOL :-
(i) Phenols give violet coloration with ferric chloride due to formation of complex compound.
C6H5OH + FeCl3 🡪[Fe(C6H5O)6 ] 3- + 3HCl
Violet complex
(ii) Bromine water test
C6H5OH + Bromine water 🡪2,4,6-Tribromophenol (White ppt.)
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(iii)C6H5OH +blue litmus 🡪 Red
Note : The above tests are not given by alcohols.
Q. Distinguish between i. n-Propyl alcohol & phenol
5) ALDEHYDES AND KETONES:-
2,4 -DNP hydrazine Test Both of them give orange or yellow ppt. with 2,4-DNP.
But following tests are given by aldehydes only.
Fehling test - Feh. A is CuSO4 soln. while Feh. B is alkaline solution of Rochelle
salt( Sodium, potassium tartarate)
Aldehyde(except aromatic aldehydes) + Fehlings Reagent 🡪 red ppt.of Cu2O
RCHO+ 2Cu2+ + 5OH- 🡪 RCOO- + Cu2O + H2O
This test is not given by aromatic aldehydes & ketones
Tollen’s test – All aldehydes reduce Tollens Reagent (Ammoniacal silver nitrate
solution) to give silver mirror.
RCHO + 2[Ag (NH3)2]+ + 3 OH- 🡪 RCOO- + 2Ag(silver mirror) + 4NH3 + 2H2O
Note: This test is given by both aliphatic &aromatic aldehydes , but not by ketones.
Formic Acid is the only carboxylic acid that reduces Tollens reagent to give
silver mirror and fehlings Reagent to give red ppt.
Q. Distinguish between i.Propanal & propanone
ii. Acetaldehyde & Benzaldehyde
iii. Benzaldehyde & Cyclohexanecarbaldehyde
5) CARBOXYLIC ACID (-COOH ) group:-
i. Sodium bicarbonate test -Compounds with -COOH group give brisk
effervescence with NaHCO3 due to evolution of CO2 gas.
RCOOH + NaHCO3 🡪 RCOONa + H2O + CO2 (Brisk effervescence)
Q. . Distinguish between i. Ethanol and acetic acid
ii. Phenol and benzoic acid
iii.Acetic acid and formic acid
6) AMINES :-
i.Hinsberg test ( Hinsberg reagent is ArSO2Cl ) – The amine is shaken with Hinsberg
Reagent in presence of excess aq. KOH solution.
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a)Primary amines give N-alkylbenzene sulphonamide which is soluble in alkali
R-NH2 + ArSO2Cl 🡪 RNH-SO2Ar + KOH 🡪 soluble product in alkali
b) Secondary amines give N,N-alkylbenzenesulphonamide which is insoluble in alkali
R2NH + ArSO2Cl 🡪 R2N-SO2Ar + KOH 🡪 insoluble product in alkali.
c) Tertiary amines do not react at all.
R3N+ ArSO2Cl 🡪No reaction
ii. CARBYLAMINE TEST or ISOCYANIDE TEST- is given by only primary
amines. Both aromatic and aliphatic primary amines when warmed with
chloroform and alcoholic KOH produce foul smelling isocyanides or
carbylamines
Ar/ RNH2 + CHCl3 + KOH 🡪 Ar/R-NC + 3KCl+3H2O
(foul smelling)
iii. Nitrous Acid (HNO2 ) TEST :-
a) RNH2 + HNO2 🡪 N2 + ROH +H2O
Aromatic primary amines form diazonium salts.
273-278 K
ArNH2 + NaNO2/HCl 🡪 ArN2Cl (diazonium salt)
b)Secondary amines form yellow oily substance with HONO
c) Tertiary amines form water soluble white salt.
iv. AZO DYE TEST :- For aromatic primary amines only.
C6H5N2Cl + C6H5OH 🡪 C6H5N2 C6H4OH (orange dye )
C6H5N2Cl + C6H5NH2 🡪 C6H5N2 C6H4NH2 ( yellow dye)
Q. How will you distinguish between: i. Ethyl amine & Diethylamine
ii. Aniline & Benzylamine
PRACTICE QUESTIONS
How will you distinguish between ;
1. Phenol and ethanol
2. Chloroethane and chlorobenzene
3. Ethanal and propanal
4. Propan-2-ol and 2-methylpropan-2-ol
5. Benzaldehyde and acetophenone
6. Ethanoic acid and ethanol
7. Phenol and aniline
8. Aniline and N-methylaniline
9. Chloroform and carbon tetrachloride (HOTS)
