Functional Groups

Let's get down to business. Today in class, we learned about functional groups. These are groups of atoms that exist in a molecule, and can give it special properties.

ALCOHOL is an organic compound that contains an OH group. The OH group is a functional group. When a hydrocarbon chain has an OH group, the name of the parent hydrocarbon changes. For example, pentane would become pentanol. 


This is methanol: CH3-OH

This is ethanol: CH3-CH2-OH 

This is 2-butanol: CH3-CH-CH2-CH3
                                  I
                                OH

This is 5-methyl-3-hexanol: CH3-CH2-CH-CH2-CH-CH3
                                                         I            I
                                                        CH3      OH


When you name an alcohol, name it so that the OH gets the lowest number possible. So if there is an OH group attached to the end of pentanol (5 carbons), name it 1-pentanol instead of 5-pentanol. (1 is lower than 5)

An ALDEHYDE is an organic compound that contains a C=O group at the end of a hydrocarbon chain- it can also be written as -CHO. These are named with "-al" at the end of the parent hydrocarbon. For example, hexane would be called hexanal. 


This is methanal: O
                            II
                       H-C-H


This is ethanal: CH3-CHO 
                         or
                         CH3-CH
                                   II
                                   O


KETONES are organic compounds that contain a C=O group at a position that's NOT at the end of a hydrocarbon chain. These are named with the ending "-one". 


This is propanone: CH3-C-CH3
                                       II
                                       O

OR

                                CH3COCH3 (condensed structure)

This is hexanone: CH3CH2COCH2CH2CH3

OR

CH3-CH2-C-CH2-CH2-CH3
                  II
                  O