[Chemistry Class Notes] Nomenclature Functional Groups Pdf for Exam

Functional groups are the main structure of most organic compounds. The name of the organic compound depends on the functional group name and their bonding. That is why specific names of the functional groups are essential. Functional groups are named depending on their structure and properties. The main basis of naming functional groups is the number of carbon atoms and their position. There are some specific rules for nomenclature functional groups like other chemical compounds. Also, the nomenclature functional groups must follow the functional group priority order. There are some general functional groups, and almost all the organic compounds are under those functional group categories. 

What is Organic Compound?

Organic compounds are a type of chemical compound formed with carbon atoms. These compounds are formed by one or more covalent bonding between carbon and other atoms. Also, organic compounds include carbon and hydrogen bonds. Carbon atoms are the main element of an organic compound because carbon has catenation properties. There is a huge number of organic compounds in chemistry. Almost all carbon compounds form organic compounds. But some carbon compounds cannot form organic compounds, such as cyanide salts, carbonate anion salts, and carbon dioxide. Difficult pure forms of carbon called allotropes are also organic compounds. Many organic compounds have different functional groups in their structure. 

What is a Functional Group?

An individual atom or a compound that is formed uniquely is called a functional group. It is also the most reactive part of an organic molecule. The compounds which have the same functional group cause the same type of reaction. Like C₂H₅OH (ethanol) and C₃H₇OH (propanol), both cause the same type of reactions as both of the compounds to have the same functional group, that is, OH. Both liberate hydrogen when the compound is treated with sodium metal. While naming an organic compound containing a functional group, naming functional groups, we have to follow the priority order in IUPAC nomenclature.

Priority Order of Functional Groups in IUPAC Nomenclature

When a molecule has multiple functional groups attached to it, we need to follow the priority order of functional groups in IUPAC nomenclature for naming functional groups. According to the table, starting from the functional groups having the highest priority are:

• Carboxylic acid (prefix: carboxy-, suffix: -carboxylic acid or -oic acid) example: ethanoic acid

• Sulfonic acid (prefix: sulfo-, suffix: -sulfonic acid) example: benzenesulfonic acid

• Ester (prefix: alkoxycarbonyl-, suffix: -oate) example: methyl ethanoate

• Acid halide (prefix: halo carbonyl-, suffix: -oyl halide) example: ethanoyl chloride

• Amide (prefix: carbamoyl-, suffix: -carboxamide or -amide) example: ethanamide

• Nitrile (prefix: cyano-, suffix: -nitrile) example: ethanenitrile

• Aldehyde (prefix: formyl-, suffix: -al or carbaldehyde) example: ethanal

• Ketone (prefix: oxo-, suffix: -one) example: 2-propanone

• Alcohol (prefix: hydroxy-, suffix: -ol) example: methanol

• Thiol (prefix: mercapto-, suffix: -thiol) example: methanethiol

• Amine (prefix: amino-, suffix: -amine) example: methylamine

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Steps For Nomenclature Functional Groups

There are some specific steps for the nomenclature of organic compounds. The naming rules of functional groups should also follow those steps. The general steps are-

• At first, the longest carbon chain is to be determined.

• All the substituents from parent chains are to be identified.

• The functional group of the compound is to be identified next.

• Determine the number of carbon compounds and carbon-hydrogen bonds.

• At the last step, the functional group will be named considering the above factors and following the IUPAC nomenclature rules. 

Solved Examples

1.Mention the Functional Group Name of these Organic Compounds: CH₃Br, CH₃NH₂, CH₃CH₂OH, CH₃OCH₃.

Solution: 

• CH₃Br (methyl bromide) – Alkyl halide

• CH₃NH₂ (methyl amine) – Amine

• CH₃CH₂OH (ethanol) – Alcohol

• CH₃OCH₃ (dimethyl ether) – Ether

2.Mention the Classification Process of the Functional Group.

Solution: There can be one or more carbon compounds and carbon-hydrogen bonds. The number of carbons detects the functional groups. The first carbon is known as alpha carbon, which is attached to the functional group. Following the same method, the second and third carbon is called beta and gamma carbon, and so on. 

3.Mention the Priority List of Functional Groups.

Solution: The priority of functional groups in IUPAC nomenclature is -COOH > -SO3H > -COOR > -COCl > -CONH₂ > -CN > HC=O > -CO > -OH > -NH₂ > C=C > C-C.