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.

Abbreviation	Group name
Ar	Aromatic substituent generic (aryl)
Bn	benzyl
Bu	butyl
Bz	benzoyl
D	deuterium
Et	ethyl
i-Bu	isobutyl
i-Pr	isopropyl
M	metal
Me	methyl
Mes	mesityl
n-Pr	propyl
Ph	phenyl
R	generic alkyl
s-Bu	butyl 2º
t-Bu	butyl 3º
X	halogen

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.

• Alcohols
• Aldehydes
• Alkanes
• Alkenes
• Alkyl halides (Haloalkanes)
• Alkynes
• Amines
• Carboxylic Acids and Derivatives
• Ethers
• Ketones