Naming of Organic Compounds (Cambridge (CIE) A Level Chemistry): Revision Note

Nomenclature of Aliphatic Compounds

• Systematic nomenclature can be used to name organic compounds and therefore make it easier to refer to them

• The alkanes provide the basis of the naming system and the stem of each name indicates how many carbon atoms are in the longest chain in one molecule of the compound

Nomenclature of organic compounds table

Side chains

• When naming compounds with side chains or functional groups, number the carbon atoms in the longest chain, starting from the end that gives the lowest possible numbers to the substituents

• In structural formulas, a side chain is often shown in brackets.

  • E.g. CH₃CH(CH₃)CH₂CH₃

• Side chains are named by changing the -ane ending of the parent alkane to -yl

• These groups are known as alkyl groups

Naming organic compounds with one alkyl side chain

• If there are more than one of the same alkyl side chain or functional groups, di- (for two), tri- (for three) or tetra- (for four) is added in front of its name

• The adjacent numbers have a comma between them

• Numbers are separated from words by a hyphen

Naming organic compounds with multiple, identical side chains

• If there is more than one type of alkyl side chain, the same numbering system applies but the different side chains are listed in alphabetic order

Naming organic compounds with multiple, different side chains

Functional groups & their nomenclature table

Class	IUAC prefix– or –suffix	Example
alkane	–ane	ethane
alkene	–ene	ethene
halogenoalkane	fluoro– chloro– bromo– iodo–	if X = F, fluoroethane
alcohol	hydroxy– –ol	ethanol
aldehyde	–al	ethanal
ketone	–one	propanone
carboxylic acid	–oic acid	ethanoic acid
ester	–oate	methyl ethanoate
amine	–amine	ethanamine
nitrile	-nitrile	ethanenitrile