Identify Functional Group in Organic Compound: Step-by-Step

Contents: Click for quick access

Apparatus Required Chemical Required Theory Observation Result Conclusion Precaution More from Chemistry Practical | 1st Year | BSc |T.U.

In this blog, we will cover how we can distinguish functional group in a given organic compound. Understanding the functional group in an organic compound is like decoding its molecular signature. We’ll delve into the methods and key indicators that help us pinpoint these chemical squads. We’ll dive into the essentials of this discussion, covering the necessary apparatus, required chemicals, the underlying theory, observations made, results obtained, and finally, draw conclusions from our exploration. Keep reading for an in-depth exploration of each aspect!

Apparatus Required

1. Test tube

2. Test tube holder

3. Burner

4. Beaker

Chemical Required

dil. HCl
dil. NaOH
dil.NaHCO3
Alcohol
ether
2,4 DNP test
Fehling’s solution test
KMnO4
given organic compound

Theory

Functional group is the reactive group of organic compound made by an atom or group of atoms due to which organic compounds displays characteristics behavior. Double bond and triple bonds are also functional groups. It is a site of chemical reactivity in a molecule. Therefore, detection of functional group is essential for the identification of organic compounds and starts from the physical character like color, state, odor, stability, etc. Organic compound may be crystalline, amorphous. Organic compound have different colors like white, red, orange etc. Organic compound have characteristics odor of their own like bitter, pungent, smell, etc. Stability behavior of compound towards various solvents also reveals its nature. Ignition towards various solvents also reveals its nature. Ignition of organic compound gives information about aliphatic, aromatic or presence of some functional group.

Observation

Sample no: 02

Physical properties

State: crystalline solid

Color: Brown

Odor: Faint phenolic.

Solubility test of organic compound (O2)

Cold H2O	Hot H2O	Dil. HCl	Dil. NaOH	Dil.NAHCO3	Alcohol	Ether
–	–	–	+	–	+	+

Preliminary test of organic compound(01)

S.N	Experiment	Observation	inference
1.	The solution of organic compound and water was treated with litmus paper	Blue litmus paper turned to red	May be carboxylic acid or phenol.
2.	Ignition test: A pinch of organic compound was taken in a spatula and burnt in a Bunsen burner.	Burnt with sooty flame	May be aromatic compound.
3.	Unsaturation test: The solution of organic compound was treated with Bayer’s reagent.	The pink color slightly discharged.	May be unsaturated compound.
4.	Dil. NaOH test: The water was added in the sample and then was treated with dil, NaOH.	The substance was dissolved and reappeared on adding dil. HCl.	May be phenol or carboxylic acid.
5.	Sodium bicarbonate test: The sample was treated with sodium bicarbonate NaHCO3.	No effervescence was obtained	Absence of carboxylic group(COOH)
6.	sample + water / alcohol was treated with 2-3 drops of FeCL3	The color was not changed	Absence of phenolic group
7.	2-4 DNP test: The solution of organic compound was treated with few drops of 2-4 DNP reagent	No color ppt formed	Absence of carboxylic group.
8.	Fehling’s solution test: Little organic compound was heated with fehling’s solution (A+ B) in a test tube.	No precipitate was formed	Absence of aldehyde or ketonic group
9.	Dil. HCl test: The substance was treated with dil. HCl	Substance didn’t dissolves	Absence of aniline
10.	Test for Nitro Group: The solution of substance in alcohol was treated with 1-2 ml of NaOH and shaken	No color ppt produced	Absence of nitro group

Confirmatory test for functional group

S.N.	Experiment	observation	inference
1.	Coupling’s test: 2-3 drops of aniline was dissolved in 1ml of conc. HCl and cooled. Few drops of ice cold solution of sodium nitrite and cold solution of organic compound was added in excess NaOH solution.	Precipitate was formed	Phenolic group was confirmed
2.	Pthalein test: About 0.2 gm of given compound heated with 0.2 gm of pthalic anhydride and a few drops of conc. H2so4 was added. After 1 min, the solution was cooled and poured in dil. NaOH solution.	The green coloration was observed	phenolic group confirmed.

Result

The functional group present in the given organic compound was phenolic group.

Conclusion

Hence, the functional group present in given organic compound can be identified by the help of physical properties, preliminary and confirmatory test.

Precaution

Chemical should be handled properly.
Physical properties should be noted carefully.
Test tube should be carried out carefully.
Test tube should be handled by test tube holder.

Check out similar practical files by clicking the link below. The next experiment also covers the same concepts discussed above.

Identify Functional Group in Organic Compound: Guide