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Functional Groups

Key Concepts

Functional Groups are the sites of chemical reactivity in an organic (carbon) compound:

alkenes- hydrocarbons containing a double bond between two carbon atoms
alkynes- hydrocarbons containing a triple bond between two carbon atoms
haloalkanes- one or more halogen atoms present
alkanols- one or more OH (hydroxyl) groups are present
alkanoic acids- COOH (carboxyl) group is present
alkanals- CO (carbonyl) group (at the end of the carbon chain)
alkanones- CO (carbonyl) group (NOT at the end of the carbon chain)
amines- NH₂ group

Naming (Nomenclature):

Alkanoic acids and alkanals are numbered beginning with the carbon of the functional group.
Alkanones and amines are numbered to give the functional group the lowest number.
Side-chains (branches) are named as for branched-chain alkanes.

Animated Tutorial

Examples

Each example below is based on a carbon chain containing 4 carbon atoms so each example can be thought of as a modified butane molecule.

Structural Formula Functional Group Name

H
| H
| H
|

C = C - C - C -H

|
H |
H |
H |
H

C=C
(double bond) 1-butene

H
| H
|

H - C ≡ C - C - C -H

|
H |
H

C ≡ C
(triple bond) 1-butyne

H
| H
| H
| H
|

H - C - C - C - C - Cl

|
H |
H |
H |
H

- Cl
(halogen) 1-chlorobutane

H
| H
| H
| H
|

H - C - C - C - C - OH

|
H |
H |
H |
H

- OH
(hydroxyl group) 1-butanol

H
| H
| H
| O
||

H - C - C - C - C - OH

|
H |
H |
H

- COOH
(carboxyl group) butanoic acid

H
| H
| H
| H
|

H - C - C - C - C = O

|
H |
H |
H

- CO
(carbonyl group) butanal

H
| H
| O
|| H
|

H - C - C - C - C - H

|
H |
H |
H

- CO
(carbonyl group) 2-butanone

H
| H
| H
| H
| H
|

H - C - C - C - C - N

|
H |
H |
H |
H |
H

- NH₂
(amine group) butylamine