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Basic IUPAC Organic Nomenclature

Functional Groups

Here is a list of the more important functional groups arranged in decreasing priority order for a nomenclature perspective.

Note that aromatic systems (arenes) such as a benzene ring should also be thought of as a functional group, but they don't fit into the priority order list shown below.

This priority order is important in nomenclature as the higher priority group is the principal functional group and it is typically numbered such that it has the lowest number (the lowest locant). 

You need to learn to recognise these functional groups not just for nomenclature but in order to recognise their reactions later.
In each case the fundamental functional group unit is shown, it is this that you need to be able to recognise - pay attention to the atoms involved and the bonding patterns.
Note the "R" is used to represent generic groups based on C (such as a methyl group) or just H.

All the 3D-JSMOL structures can be manipulated using your computer mouse (e.g. zoom, rotate)

Functional
Group

Formula

Structure

Carboxylic Acids
Acid Anhydrides
Esters
Acyl Halides
Amides
Nitriles
Aldehydes
Ketones
Alcohols
Thiols
Amines
Ethers
Sulfides
Alkenes
Alkynes
Alkyl Halides
Nitro
Alkanes

organic chemistry ©Dr. Ian Hunt, Department of Chemistry University of Calgary