Which of the following forms a homologous series?

Ethane, ethylene, acetylene

Ethane, propane, butanone

Methane, ethanol, propanoic acid

Butane, 2-methyl butane, 2,3-dimethyl butane



A homologous series is a series of organic compounds having similar structures and similar chemical properties . Two successive compounds differ by CH 2 Group .

  1. If we consider ethane, ethylene and acetylene , ethane is an alkane, ethylene is an alkene and acetylene is an alkyne. Since all three of them have different chemical properties , they do not form a homologous series.

Ethane - Teachoo.png

Structure of Ethene - Teachoo.png

Structure of Ethyne - Teachoo.png

2. Among ethane, propane and butanone , ethane and propane are alkanes but butanone is a ketone. Because their chemical properties are different , they do not form a homologous series.

Ethane - Teachoo.png


3. Methane, ethanol and propanoic acid do not form a homologous series because methane is an alkane, ethanol and alcohol and propanoic acid is a carboxylic acid and so they have different chemical properties


4. Butane, 2-methyl butane and 2,3-dimethyl butane all are alkanes and they also have a difference of CH 2 group between two successive compounds . Therefore, they belong to the same homologous series.


So, the correct option - (4) Butane, 2-methyl butane, 2,3-methyl butane

Learn in your speed, with individual attention - Teachoo Maths 1-on-1 Class

Ask a doubt
Maninder Singh's photo - Co-founder, Teachoo

Made by

Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo