December 25, 2012

SOME USEFUL TIPS FOR SOLVING ORGANIC PROBLEMS



S. No
Experiment /
Properties
Observation
Inference
1
Smell / Odour
a) Pleasant
May be Esters, Ethers Ketones  or Nitro alkanes
b) Bitter almonds
Benzaldhyde, C6H5 –CHO
Nitro benzene, C6H5 –NO2
c) Carbolic acid
Phenols
d) Fishy
Amines
e) Jasmine
Benzyl acetate,
C6H5 CH2COOCH3
f) Foul / Offensive
Acroleine,
CH2 = CH – CHO or
Alkyl isocyanide, R –N ≡ C or Aryl isocyanide, Ar –N ≡ C
g) Pungent mustard like
Alkyl isothiocyanate,
R –N = C = S
2
With metallic Sodium
a) H2 gas evolved
Alcohol (– OH group) is present
b) No reaction
May be ether (– O – group)
3
With NaHCO3 or Na2CO3 solution
Brisk effervescence of CO2
Carboxylic acid (– COOH group) is present

4

Victor Meyer’s Test
a) Red colour
1o alcohol (– CH2–OH group) is present
b) Blue colour
2o alcohol (> CH–OH group) is present
c) Colourless
3o alcohol (> C–OH group) is present           |
5
With Conc. HCl and anhydrous ZnCl2
(Lucas Test)
a) Immediate turbidity or cloudiness
3o alcohol (> C–OH group) is present            |
b) Turbidity or cloudiness after 5-10 minutes
2o alcohol ( > CH–OH group) is present
6
With Carboxylic acid and Conc.H2SO4 (Esterification)
Pleasant smelling ester is formed
Alcohols (– OH) present
7
With neutral FeCl3
Violet colour
Phenol, C6H5 – OH
8
a) With neutral FeCl3
Violet colour
Salicylic acid,
o- HO– C6H4 – COOH
b) With NaHCO3 or Na2CO3 solution
Brisk effervescence of CO2
9
With Bromine water
(Br2 / H2O)
a) White precipitate
Phenol, C6H5 – OH
b) Yellow precipitate
Aniline, C6H5 – NH2
c) Decolourises
Unsaturated compund
(–C = C– , –C ≡ C–)  
10
With Tollen’s reagent (Ammoniacal AgNO3)
Silver mirror is formed
Aldehydes (– CHO),
Formic acid (HCOOH),
Glucose,
Fructose or
Tartaric acid
11
With Fehling’s solution
Blue colour becomes Red colour
Aliphatic Aldehydes
(– C – H)
     | |
     O
12
With Schiff’s reagent
Red / Pink colour is restored
Aldehydes, CHO
13
With I2 and NaOH
(Haloform reaction)
Iodoform is formed
Ketones (CH3 – C –),
                          | |
                          O
Ethyl alcohol,
Isopropyl alcohol,   
(CH3– CH –),
            |
           OH
14
When oxidised
Gives acid
May be aldehyde or ketone
 (– C – )
      | |
      O
15
When strongly oxidised by
K2 Cr2 O7 or KMnO4
Gives acid
May be alcohol (– OH)
16

When reduced by reducing agents such as Li Al H4 or Na/Hg in H2O

a) Gives 1o alcohol
(– CH2 – OH)
Aldehyde (– CHO)
b) Gives 2o alcohol
(> CH – OH)
Ketone (– C –)
                 | |
                 O
17
Dry distillation of Calcium salt
a) Gives Acetone
Acetic acid, CH3 COOH
b) Gives Benzophenone
Benzoic acid, C6H5 COOH
c) Gives Formaldehyde
Formic acid, HCOOH
18
Heated with Soda lime (NaOH + CaO) (Decarboxylation)
Benzene is got
Benzoic acid, C6H5 COOH
19
With nitrous acid
(NaNO2 + HCl)
a) Alcohol is formed with the liberation of N2
1o amine (– NH2 group) is present 

20

With CHCl3 and alcoholic KOH or NaOH
(Carbylamine reaction)
b) Oily nitroso amine
2o amine (> NH group) is present
Foul smelling isocyanide is given out
Primary amine (– NH2 group) is present
21
With CS2 and HgCl2 
(Mustard oil reaction)
Pungent mustard like odour
Primary amine (– NH2 group) is present
2
With metallic Sodium
a) H2 gas evolved
Alcohol (– OH group) is present
22
Optically active compounds
----
CH3CH(OH)CN,
2–Butanol,
Lactic acid,
Tartaric acid,
Glucose,
Fructose,
α - Aminoacids (Except – Glycine)
23
Exposure to air or light
a) Liquid or Crystalline Solid turns Pink or Red
Phenols
b) Liquid turns Brown
Aniline, C6H5 NH2
c) Crystalline Solid turns Brown
Benzene diazonium chloride, C6H5N2Cl

 * The above tips are useful:-
 # for solving organic problems easily;
# # to answer the questions like   
Distinguish one compound from the other, Test for compounds, etc,.

1 comment:

  1. Thank u sir for valuable tips and guidance

    ReplyDelete