Functional Groups

FUNCTIONAL GROUPS

Functional groups have already been discussed to some degree as the side chains represent functional groups in many cases because they impart reactivity of the molecule. A functional group can be described as a side chain on the molecule that gives the organic substance some type of reactivity. They can be listed as prefixes or suffixes. The suffixes have been talked about but the prefixes haven’t been mentioned. The following is a list of functional groups and the way they are named:

• Carboxylic acids—these have no prefixes but end in -oic acid.

• Aldehydes—these have no prefixes but end in -al as a suffix.

• Ketones—these have no prefixes but end in -one as a suffix.

• Alcohols—the prefix is “hydroxy”, while the suffix is -ol.

• Amines—the prefix is “amino”, while the suffix is “amine”.

• Ethers—the prefix is “alkoxy”, while the suffix is “ether”.

• Halogens—these have no suffixes but only have the prefixes “fluoro”, “chloro”,

“bromo”, and “iodo”.

A functional group can be a single atom or a group of atoms, such as Cl or COOH. You should know that many compounds have both a common name and an IUPAC “systematic name”. For example, methanal and ethanal are “formaldehyde” and “acetaldehyde”, respectively. With aromatic rings, these start with “benzo” or end with “benzene”. The chain is numbered so that the lowest numbers are used, for example, if there are any side chains, they are called 1R or, 1-methylbenzene, 1,2-dimethylbenzene, or 1,3, dimethylbenzene, etcetera. Common naming uses “ortho” to describe 1,2 placements, “meta” to describe 1,3 placements, and “para” to describe 1,4 placements of side chains. This is further described in figure 29: