Functional Groups (DP IB Chemistry: SL): Revision Note

Functional groups

What are functional groups in organic chemistry?

• Functional groups are atoms or groups of atoms that are found in organic compounds

• They give organic compounds their characteristic physical and chemical properties

• Organic compounds that contain the same functional group belong to the same class

  • Careful: This should not be confused with belonging to the same homologous series

• For example:

  • The class of organic compounds called the alkenes all contain the carbon-carbon double bond –C=C– functional group

  • The class of organic compounds called the aldehydes all contain the –CHO functional group

• Compounds with only single bonds between carbon atoms are described as saturated, while those with carbon–carbon double or triple bonds are unsaturated

Classes of organic compounds table

Class	Functional group name	Functional group formula	IUPAC prefix– or –suffix	Example
alkane	alkyl	–	–ane	ethane
alkene	alkenyl		–ene	ethene
alkyne	alkynyl		–yne	ethyne
halogenoalkane	halogeno	F– Cl– Br– I–	fluoro– chloro– bromo– iodo–	if X = F, fluoroethane
alcohol	hydroxyl		hydroxy– –ol	ethanol
aldehyde	carbonyl (aldehyde)		–al	ethanal
ketone	carbonyl (ketone)		–one	propanone
carboxylic acid	carboxyl (acid)		–oic acid	ethanoic acid
ether	alkoxy		–	ethoxyethane
amine	amino		–amine	ethanamine
amide	amido		–amide	ethanamide
ester	ester		–oate	methyl ethanoate
aromatics*	phenyl		phenyl– –benzene	phenylethane ethylbenzene

* The specification asks you to identify the phenyl group by name and structure; it does not require specific knowledge of arenes as a class of organic compound