Class 10, Science, Chapter-4, Lecture-2, Homologous Series of Organic Compounds (Notes)
TYPES OF CHAINS Formed by carbon.
- Straight chain
- Branched chain
- Closed chain
SATURATED CARBON COMPOUNDS
The carbon compounds which contain only carbon-carbon covalent single bonds are called saturated carbon compound.
UNSATURATED CARBON COMPOUNDS
The carbon compounds which contain one or more carbon-carbon covalent multiple bonds are called unsaturated carbon compound.
HYDROCARBONS
The organic compounds which contain only carbon and hydrogen are called hydrocarbons.
Types of Hydrocarbons:
(i) Saturated hydrocarbons (ALKANES)
The hydrocarbons which contain only carbon-carbon covalent single bonds are called alkenes.
General Formula:
(ii) Unsaturated hydrocarbons
(a) ALKENES
The hydrocarbons which contain one or more carbon-carbon covalent double bonds and do not contain triple bonds are called alkenes.
General Formula:
(b)ALKYNES
The hydrocarbons which contain one or more carbon-carbon covalent triple bonds and do not contain double bonds are called alkynes.
General Formula:
HETEROATOM
The element that replaces a hydrogen atom from an organic compound is termed as a heteroatom.
Example: ${\rm{Cl}}$ is the heteroatom in ${\rm{C}}{{\rm{H}}_3}{\rm{Cl}}$
ALKYL RADICAL
A group of atoms formed by removal of one hydrogen atom from an alkane molecule which acts like a single atom in chemical reactions is termed as an alkyl radical.
General Formula: $ - {C_n}{H_{2n + 1}}$
Example: $ - C{H_3}$ is an alkyl radical formed by removal of an H atom from CH4 molecule.
ALKYLE RADICAL | NAME |
---|---|
—CH3 | Methyl |
—C2H5 | Ethyl |
—C3H7 | Propyl |
—C4H9 | Butyl |
FUNCTIONAL GROUP
An atom or a group of atoms in an organic molecule that is responsible for the compound’s characteristic reactions and determines its properties is known as a functional group.
HOMOLOGOUS SERIES
A series of organic compounds having the same functional group and similar chemical properties in which successive members differ in their molecular formula by a $ - C{H_2}$ group is called a homologous series.
Characteristics of Homologous Series
- All the members of a homologous series have the same general formula.
- Successive members differ in their molecular formula by a $ - C{H_2}$ group.
- Successive members differ in their molecular mass by 14 U (unified atomic mass).
- All the members have similar chemical properties.
- Physical properties of the member change gradually.
- All the members of a series can be prepared by the same general method of preparation.