Introduction carboxylic acids structure

Carboxylic acids are organic compounds containing the functional group shown at the right.  
The general formula for a carboxylic acid can be written as RCOOH or RCO2H where R is either H or a hydrocarbon group.  The carboxylic acid functional group is always at the end of the chain.  
 
Names of carboxylic acids
include the functional group ending and a stem preceded by prefixes and corresponding locators.

Functional group ending: -oic acid.
Stem indicates
the number of carbons (meth - 1, eth - 2, prop - 3 .....)
 
Example:

propanoic acid

any unsaturation in the hydrocarbon chain
an no unsaturation in hydrocarbon chain,
en double bond,
yn triple bond)

the position of any unsaturation (CO2H carbon is number 1)
 
Example:

3-methylpent-3-enoic acid

Prefixes indicate substituents on the chain
OH hydroxy
Cl chloro
Br bromo
=O oxo

Locators before each substituent indicate the position of that substituent on the longest chain containing the CO2H functionality. 
Dr Sheila Woodgate
© The University of Auckland 2002