Homologous Series and Functional Group

Homologous series is a family of organic compounds with a similar chemical structure and react by the same general method. Each member differs from the next by a CH2 group.
A functional group is an atom or group of atoms that determine the chemical properties of a molecule. The functional group’s reactivity drives the reactions of the organic molecules.
The smallest member of the homologous series is methane in which there is one carbon atom.
Organic compounds in the same homologous series show trends or graduations in physical properties. This includes melting and boiling points, which generally increase as the size of the molecule increases.
Members of the same homologous series all have similar chemical properties, however compounds in different series react in distinct ways due to the difference in their functional group.
Every homologous series has a general formula expressive of any member of the series in general terms. For alkanes, the general formula is CnH2n+2.
Common homologous series include alkanes, alkenes, alcohols, aldehydes, ketones, carboxylic acids and amines. Naming of the compounds within these series is done according to IUPAC rules.
Functional groups are crucial in identifying organic compounds and predicting their reactions. Common functional groups include hydroxyl (-OH) in alcohols, carbonyl (=O) in aldehydes and ketones, carboxyl (-COOH) in carboxylic acids, and amine (-NH2) in amines.
In terms of reactivity, alkanes are less reactive due to their single covalent bonds, alkenes are more reactive due to the presence of a carbon-carbon double bond, while the hydroxyl group in alcohols make them quite polar, impacting their solubility and reactivity.
Isomerism is common in homologous series and arises due to the many ways the hydrogen atoms can attach to the carbon skeleton. Different isomers can have different physical and chemical properties.
The more carbons a molecule in a homologous series has, the more isomers it can have.