Question

Give the names and structural formula of the first three members of the homologous series of alkanes.

Answer 1

Definition of homologous series

• Homologous series is a series of compounds with very similar chemical properties and functional groups differing from the successive member by ${\mathrm{CH}}_2$
• Carbon chains having varying lengths have a general formula
• These series are common in organic compounds

Definition for alkanes

• These are saturated hydrocarbons
• They contain single-bonded carbon and hydrogen atoms
• subdivided into three groups: chain alkanes, cycloalkanes, and branched alkanes.
• The general formula for these types of hydrocarbon is${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}+2}$

Therefore, the names and structural formulas of the first three members of the homologous series of alkanes are:

Alkane	Molecular formula	Composition	Carbon atoms in chain	Hydrogen atoms in chain
Methane	${\mathrm{CH}}_4$	${\mathrm{CH}}_4$	1	4
Ethane	${\mathrm{C}}_2{\mathrm{H}}_6$	${\mathrm{CH}}_3-{\mathrm{CH}}_3$	2	6
Propane	${\mathrm{C}}_3{\mathrm{H}}_8$	${\mathrm{CH}}_3-{\mathrm{CH}}_2-{\mathrm{CH}}_3$	3	8