3.2.3 and 3.2.4 homologous series

chem classificationsofmatter

Structure 3.2.3 - a homologous series is a family of compounds in which successive members differ by a common structural unit, typically . each homologous series can be described by a general formula

alkanes, alkynes, halogenoalkanes, alcohols, aldehydes, ketones, carboxylic acids, ethers, amines, amides and esters

3.2.4 - successive members of a homologous series show a trend in physical properties

homologous series differ by a group

organic compounds are classified into ‘families’ of compounds, known as homologous series. the members possess certain common features

the molecular mass increases by a fixed amount moving up a homologous series

members of a homologous series can be represented by the same general formula

eg:

• alkanes:
• alcohols

members of a homologous series show a trend in physical properties

as successive members of a homologous series differ by a group, they have successively longer carbon chains. this is reflected in a gradual trend in the physical properties:

• melting point/boiling point
• density
• viscosity

longer chains means stronger London dispersion forces

functional groups affect the physical properties of organic compounds

functional groups have a significant effect on physical properties