Functional Groups

What are functional groups?

Despite the great variety of organic molecules that arise from the different ways in which carbon is bonded to different atoms, they can be grouped into families with similar characteristics.

A functional group is an atom or grouping of atoms within a molecule that is responsible for characteristic properties of such molecules, such as reactivity or some physical properties. The same functional groups will give similar chemical reactions.

The following figure shows the most relevant functional groups in organic chemistry, in alphabetical order.

The letter R stands for an alkyl group, and different alkyl groups are named as R, R', R" (or also R1, R2, R3), etc. Ar stands for an aromatic group, and X = F, Cl, Br and I. 

It should be noted that alkanes and cycloalkanes are not considered as such functional groups, but correspond to the skeleton of organic molecules without functionalization.

Abbreviations

The use of abbreviations is frequent. The following is a list of the most frequently used abbreviations.

Table 2: Frequently used abbreviations.
AbbreviationGroup name
ArAromatic substituent
generic (aryl)
Bnbenzyl
Bubutyl
Bzbenzoyl
Ddeuterium
Etethyl
i-Buisobutyl
i-Prisopropyl
Mmetal
Memethyl
Mesmesityl
n-Prpropyl
Phphenyl
Rgeneric alkyl
s-Bubutyl 2º
t-Bubutyl 3º
Xhalogen

Summary of the most relevant functional groups

The main functional groups are summarized below, and the link provides additional information on the most significant properties: characteristics, nomenclature, reactivity and organic analysis.