Question

Define homologous series of organic compounds. List its two characteristics. Write the name and formula of the first member of the series of alkenes.

Answer 1

A homologous series is a series of carbon compounds that have different number of carbon atoms but contain the same functional group.

For example, methane, ethane, propane, butane, etc. are all part of the alkane homologous series.

Methane CH₄

Ethane CH₃CH₃

Propane CH₃CH₂CH₃

Butane CH₃CH₂CH₂CH₃

There is a difference of −CH₂ unit between each successive compound.

Characteristics of homologous series:

All the members of the homologous series have same functional groups and hence similar chemical properties.

Two successive members of a homologous series differ by a −CH₂ unit and 14u.

The first member of the series of alkenes in ethene. Its formula is C₂H₄.