Qualitative Analysis of unknown organic compound for function group detection (Carboxylic acid)

Experiment No. 5

Object:

Qualitative Analysis of unknown organic compound for function group detection (Carboxylic acid)

Reference: 

1. Agarwal O.P., Practical Organic chemistry, published by Krishna educational publisher, Edition 2014, page no.30-31
2.  Dr. Jain K.S., Dr. Miniyar P.B., A practical book of Pharmaceutical organic chemistry , Nirali publication, edition 4th, page No. 1.21-1.23

Requirement:

Test tube, Beaker, Glass rod

Organic compound, Sod bicarbonate, HCl

Theory:

Organic compounds containing carboxyl functional groups are called carboxylic acids. The term carboxyl, derives its name from the combination of words carbonyl and hydroxyl because carboxylic functional group O contains both of these groups (—C—OH ). These acids turn blue litmus red and react with sodium hydrogencarbonate solution to produce effervescence due to the formation of carbon dioxide. This is a test that distinguishes carboxylic acids from phenols.

Procedure

 1. SODIUM BICARBONATE TEST

1. Take 0.2 g / 0.2 ml of unknown organic compound in test tube
2. Add 2-3 ml of aqueous NaHCO3 (10%)

Observation: 1. Effervescence of CO2

                             2. Reappearance of the solid substance after adding dil HCl

Inference: COOH group is present

Reaction:

R–COOH+NaHCO3​→R–COONa+CO2​↑+H2​O

2. ESTER TEST

1. Take 0.2 gm/0.2 ml of compound  in test tube.
2. Add 5 ml of ethanol.
3. Add 2 drops of con. H2SO4
4. Heat it on boiling water bath.

Reaction: 

R–COOH+C2​H5​OH—————->​​R–COOC2​H5​+H2​O (in presence of H2​SO4)

Observation: Fruity smell of ester

Inference: -COOH group is present

3. Ferric chloride test

1. Take 0.05 gm of compound
2. Add 1ml of water and shake well.
3. Add 1-2 drops of alcoholic Fecl3 solution.

Observation:

1. Buff colored precipitate                                             Benzoic acid/pthalic acid
2. Violet colored precipitate                                          Salicylic acid
3. Violet colored ppt obtained after heating              Acetyl Salicylic acid
4. Yellow colored ppt                                                      Cinammic acid
5. Faint raddish                                                               Succinic acid
6. Deep Yellow                                                                  Citric acid
7. No change in FeCl3                                                     Oxallic acid

Result

——————functional group was found in given organic compound.