Functional Groups

Organic - Nomenclature

In this segment we will explain what functional groups are and how to name molecules with specific functional groups. A functional group is a molecule or group of molecules bonded in a specific way to each other that determines generic trends in the compounds reactivity and physical information (boiling points, density, etc). In organic chemistry, this generally means a special group of molecules other can carbon bonded to other carbons and hydrogen (simple carbon chain). An example of a functional group would be –OH, the alcohol functional group. A molecule with an alcohol functional group ends in the suffix –ol. An example of a molecule with the alcohol functional group would be methanol, CH3OH.

Parent Compounds

Methanol’s parent compound is methane. A parent compound is what the molecule would be if there was no unique functional group. So instead of having an –OH group, it would just be H, leaving methane. The parent compound for this molecule is methane, so methanol will begin with the prefix methan-, and end with –ol, which indicates it has an alcohol functional group.

Placement on the Molecule

Like the placement of branches on a carbon chain, location of the functional group is included in the nomenclature. Use the smallest number just like in branch nomenclature. If the functional group is placed on the beginning of a chain, you don’t need to include the number in your nomenclature. For example, our example of methanol is on the beginning of the one carbon long chain, so it wouldn’t be named 1-methanol.

To summarize, the suffix of your molecule’s name is dependant on the functional group present. Methane has the alkane functional group, so the name is composed of meth- for the carbon chain, and –ane for the alkane functional group. Similarly, methanol has a methane carbon parent chain resulting in the methan- prefix, and –ol to indicate the alcohol functional group.

A table of the different kinds of functional groups, their suffixes, and an example can be found on this website:

http://masterorganicchemistry.com/2011/02/14/table-of-functional-group-priorities-for-nomenclature/

Otherwise there is a table of the name of the functional group and their suffixes with an example below.

Functional Group  Naming   Example Name  
Carboxylic Acid -oic acid propanoic acid
Ketone -one propanone
Alcohol -ol ethanol
Aldehyde -al propanal
Ether -oxy-,-ane ethoxybutane
Ester -anoate ethylbutanoate
Halide

fluoro-

chloro-

fluorobutane

chlorobutane

bromobutane

Amine -amine propylamine

 

Concept Definition

Study the primary definition of this concept, broken into general, basic, and advanced English definitions. Also see the mathematical definition and any requisite background information, such as conditions or previous definitions.

Basic

A functional group is a specific group of elements bonded together in a particular way in a molecule.

Advanced

A functional group is a specific group of elements organized in a specific way on the molecule that determine the molecules chemical reactivity.

 

Vocabulary

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 Important Vocabulary

Term Context
Functional Group A specific group of molecules bonded together in a specific way on the molecule, that determines the chemical reactivity of the compound.
Parent Compound What the molecule would be if the functional group wasn't on the molecule (replaced with carbons and hydrogens).

 

Videos

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Functional Groups

functional groups

 

Study Aides

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 Study Aides

Some practice problems (with introduction) can be found here:

http://chemed.chem.purdue.edu/genchem/topicreview/bp/2organic/function.html

These questions are slightly more difficult, but include functional group questions:

http://chemed.chem.purdue.edu/genchem/topicreview/bp/2organic/function.html

More functional group problems here:

http://highered.mcgraw-hill.com/sites/0072828374/student_view0/chapter4/practice_problems.html

 

Sample Problems

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 Sample Problems

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