Systematic Nomenclature
- 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
- If there are any side-chains or functional groups present, then the position of these groups is indicated by numbering the carbon atoms in the longest chain starting at the end that gives the lowest possible numbers in the name
- The hydrocarbon side-chain is shown in brackets in the structural formula
CH3CH(CH3)CH2CH3
- The side-chain is named by adding ‘-yl’ to the normal alkane stem
- This type of group is called an alkyl group
Naming Side Chains
- 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 Multiple Side Chains
- If there is more than one type of alkyl side-chain, they are listed in alphabetic order
Naming Side Chains in Alphabetical Order
Exam Tip
An aliphatic compound is straight or branched-chain and also includes cyclic organic compounds that do not contain a benzene ring.
Functional Groups & their Nomenclature Table
Worked Example
Naming organic molecules
Name the following molecules using correct systematic nomenclature: 
Answer
Chemical Formulae
- The general formula is a formula that represents a homologous series of compounds using letters and numbers
- E.g. the general formula of alkanes is CnH2n+2
- A homologous series is a group of organic compounds that have the same functional group, the same general formula and the same chemical properties
- The structural formula is a formula that shows how the atoms are bonded to each carbon atom in a molecule
- The displayed formula is a 2D representation of an organic molecule showing all its atoms (by their symbols) and their bonds (by single, double or triple bonds)
- The skeletal formula is a simplified displayed formula with all the carbon and hydrogen atoms removed, with the exception of hydrogens that are part of a functional groups, e.g. OH
Overview of the Formulae of Organic Compounds Table
Worked Example
Drawing skeletal formulae of molecules
Draw the skeletal formula of the following molecules:
- CH3(CH2)3OH
- (CH3)2CHCH2OH
- CH3CH2OCH2CH3
Answer:
Worked Example
Drawing displayed formulae of molecules
Draw the displayed formula of the following molecules:
Answer
