Functional Groups
An atom or a group of atoms which when present in a compound gives specific physical and chemical properties to it regardless of the length and nature of the carbon chain is called a functional group.
Classification of Functional Groups
Main Functional Groups:
(i) Hydroxyl group (-OH): All organic compounds containing -OH group are known as alcohols. For example, Methanol (CH3OH), Ethanol (CH3−CH2−OH), etc.
(ii) Aldehyde group (-CHO): All organic compounds containing -CHO group are known as aldehydes. For example, Methanal (HCHO), Ethanal (CH3CHO), etc.
(iii) Ketone group (-C=O): All organic compounds containing (-C=O) group flanked by two alkyl groups are known as ketones. For example, Propanone (CH3COCH3), Butanone (CH3COCH2CH3), etc.
(iv) Carboxyl group (-COOH): All organic acids contain a carboxyl group (-COOH). Hence, they are also called carboxylic acids.
For example, Ethanoic acid (CH3COOH), Propanoic acid (CH3CH2COOH), etc.
(v) Halogen group (F, CI, Br, I): The alkanes in which one or more than one hydrogen atom is substituted by- X (F, CI, Br or I) are known as haloalkanes. For example, Chloromethane (CH3Cl), Bromomethane (CH3Br), etc.
Homologous Series
Homologous series constitutes organic compounds with the same general formula, similar chemical characteristics but different physical properties. The adjacent members differ in their molecular formula by −CH2.
Examples of homologous series
Methane, ethane, propane, butane, etc. are all part of the alkane homologous series.
The general formula of this series is CnH2n+2.
Methane (CH4), Ethane (CH3CH3), Propane (CH3CH2CH3), Butane (CH3CH2CH2CH3).
It can be noticed that there is a difference of −CH2 unit between each successive compound.
Nomenclature of Carbon Compounds
International Union of Pure and Applied Chemistry (IUPAC) decided some rules to name the carbon compounds. This was done to maintain the uniformity throughout the world. Names which are given on this basis are popularly known as IUPAC name.