ChemWhiz ReferenceOrganic Chemistry
Common Organic Functional Groups
The essential organic functional groups with their general formulas, naming conventions, and representative examples. Fundamental to understanding organic chemistry nomenclature.
01Use this when
Identifying or naming an organic compound from the group present, and predicting its reactivity.
02Conditions
R stands for any hydrocarbon group (alkyl or aryl).
03Watch out
When several groups are present, precedence decides the suffix (a carboxylic acid outranks an alcohol).
Functional Groups and Their Suffixes
General formula, IUPAC suffix, and a worked example for each common functional group.
| Alkane | CnH2n+2 | -ane | Ethane | C2H6 |
| Alkene | CnH2n | -ene | Ethene (ethylene) | C2H4 |
| Alkyne | CnH2n-2 | -yne | Ethyne (acetylene) | C2H2 |
| Alcohol | R–OH | -ol | Ethanol | C2H5OH |
| Aldehyde | R–CHO | -al | Ethanal (acetaldehyde) | CH3CHO |
| Ketone | R–CO–R' | -one | Propanone (acetone) | CH3COCH3 |
| Carboxylic acid | R–COOH | -oic acid | Ethanoic acid (acetic acid) | CH3COOH |
| Ester | R–COO–R' | -oate | Ethyl ethanoate | CH3COOC2H5 |
| Amine | R–NH2 | -amine | Methylamine | CH3NH2 |
| Amide | R–CONH2 | -amide | Ethanamide (acetamide) | CH3CONH2 |
| Ether | R–O–R' | prefix: alkoxy- | Diethyl ether | C2H5OC2H5 |
| Haloalkane | R–X (X = F, Cl, Br, I) | prefix: fluoro-, chloro-, bromo-, iodo- | Chloromethane | CH3Cl |
| Thiol | R–SH | -thiol | Ethanethiol | C2H5SH |
| Nitrile | R–C≡N | -nitrile | Ethanenitrile (acetonitrile) | CH3CN |
Important Notes
- R represents any alkyl group (hydrocarbon chain). R' represents a second, possibly different alkyl group.
- IUPAC priority order (highest to lowest): carboxylic acid > ester > amide > nitrile > aldehyde > ketone > alcohol > thiol > amine > alkene > alkyne > alkane.
- The highest-priority group determines the suffix; lower-priority groups are named as prefixes.
- The general formulas CnH2n (alkene) and CnH2n-2 (alkyne) apply to acyclic hydrocarbons with exactly one double or one triple bond; rings or additional unsaturation change the hydrogen count.
- Aldehydes always occur at the end of a carbon chain (terminal); ketones occur within the chain (internal).
- Common names are shown in parentheses. IUPAC names should be used for formal nomenclature.
- Naming follows IUPAC 2013 Recommendations for the Nomenclature of Organic Chemistry.
Verification references: IUPAC Nomenclature of Organic Chemistry, 2013 Recommendations (Brief Guide to the Nomenclature of Organic Chemistry, IUPAC 2021).