A homologous series in organic chemistry is a group of organic compounds (compounds that contain C atoms) that differ from each other by one methylene (CH2 ) group. For example, methane, ethane, and propane are part of a homologous series. The only difference among these molecules is that they have different numbers of CH2 groups.
Each member of a homologous series is called a homologue, which can also be spelled ''homolog.'' For example, methane and ethane are homologues and belong to the same homologous serie