Functional Groups

Functional Groups

Functional Groups Definition and Meaning

Functional groups in organic chemistry are those which are responsible for the changes in the physical and chemical properties of an organic compound. There are various such groups in organic chemistry. It can be defined as:

“An atom or group of atoms which show a characteristic unique reactivity when treated with some reagents and also which impart some unique chemical, as well as physical properties to the primary molecule, is defined as a functional group.”

Molecules are divided into two types in organic chemistry:

  • Organic molecules
  • Inorganic molecules

The molecules which consist of carbon atoms along with hydrogen atoms are called as organic molecules like hydrocarbons, and the functional groups are mainly dealt with the organic molecules since they exhibit non-polarity kind of nature and also due to the high electronegativity. These groups also decide the properties and the functionality of a chemical compound. Some of the examples of functional groups are carboxylic acid (RCOO-) and ester (R-COO-R). This comprises of an acyl group (RCO-) and an alkoxy group (-OR’).

Types of Functional Groups

A variety of functional groups exist in organic chemistry. Most of them are carbon-based compounds. Some groups form a single bond with most of the hetero-atoms such as oxygen, iodine, nitrogen, sulfur, etc. There is also some other kind of groups having multiple bonds with the hetero-atoms such as oxygen, nitrogen atoms, etc.

The lists of some of the common functional groups are contained in the table below:

Group formula Class name Example Common name
C=C Alkene CH2=CH2 Ethylene
Arene C6H6 Benzene
-OH Alcohol CH3OH Wood alcohol
-Cl Chloro CH3Cl Methyl chloride
C-X Halide CH3-I Methyl iodide
C-O-C Ether CH3-CH2-O-CH2-CH3 Ether
C-N Amine CH3-NH2 Methyl amine
Aldehyde CH3-CHO Acetaldehyde
Ketone CH3-CO-CH3 Acetone
Carboxylic acid CH3-COOH Acetic acid
Ester CH3-CO2-CH2-CH3 Ethyl acetate

Let us study in detail about some of the functional groups of the organic chemistry as given below:

  • Alkene Functional Group: The alkene functional group is characterized by the presence of two carbon atoms in it. In this group, there are two covalent bonds formed between two carbon atoms. This bond represents the alkene group (C=C).
  • Alcohol Functional Group: The presence of the hydroxyl group (-OH) in an organic compound indicates the alcohol functional group. The two pairs of electrons on the oxygen atom are involved in various chemical reactions thus forming hydrogen bonds with the different molecules of alcohol. Hence this group is said to be alcoholic in nature.
  • Hydroxyl Group: This is one of the functional groups present in the alcohols. This group is so called because of its formation of the hydrogen bonds with the other molecules. It is involved in the process of organic synthesis, catalysis of enzyme and also in various biological structures.
  • NH2 Functional Group: This group is also called as amine or amino group. This group is obtained by replacing one atom of hydrogen from ammonia molecule with an aryl group or an alkyl. There are two kinds of NH2 Functional Group namely Aliphatic R-NH2 and Aromatic Ar-NH2.
  • Functional Group COOH: This group is also known as Carboxyl group. The presence of OH characterizes it. COOH group is formed by combining the carbonyl group and the hydroxyl. This group exhibits acidic properties.
  • Methyl Group: Methyl Functional group, is indicated by the presence of side chain in an organic molecule or a compound. The group acts as a substitute to the parent chain. This branching of the group affects the properties, boiling points and the melting points of the organic compounds.
  • Phosphate Group: The group which makes up multiple bonds with various hetero-atoms such as phosphorus is called as Phosphate Functional Group. In this group, the oxygen atoms are bonded to the phosphorus atoms along with alkyl group. Some of the examples of organic compounds containing this functional group are adenosine triphosphate, DNA, phosphorus acid ( H3PO3 ), phosphoric acid ( H3PO4 ), etc.

To learn more about how these compounds are named visit our sites article on Nomenclature of Organic Compounds having Functional Groups. Stay tuned with BYJU’S for more information on Organic and Inorganic compounds.

Practise This Question

Carbolic acid is