Understanding Organic Chemistry Nomenclature
The foundation of Organic Chemistry AQA A Level lies in understanding how compounds are named and classified. The International Union of Pure and Applied Chemistry (IUPAC) system provides standardized rules for naming organic compounds.
Definition: A functional group is an atom or group of atoms that determines the characteristic chemical properties of an organic compound family. Examples include -OH (alcohol), -COOH (carboxylic acid), and -NH2 (amine).
The naming process follows a systematic approach based on several key principles. First, identify the longest continuous carbon chain, which becomes the parent chain. This determines the base name using prefixes like meth- (1C), eth- (2C), prop- (3C), and so on. Next, identify the highest-priority functional group present, which determines the suffix of the name. The order of precedence follows: carboxylic acids > esters > amides > nitriles > aldehydes > ketones > alcohols > amines.
Highlight: When naming branched molecules, number the carbon chain to give the main functional group the lowest possible number. List substituents alphabetically, using multiplying prefixes (di-, tri-, tetra-) when multiple identical groups are present.
For geometric isomers, the Cahn-Ingold-Prelog (CIP) rules determine E/Z configuration. These rules compare atomic numbers of groups attached to double-bonded carbons, with higher atomic numbers receiving higher priority. E-isomers have higher-priority groups on opposite sides of the double bond, while Z-isomers have them on the same side.