Discuss the rules for IUPAC nomenclature of compounds containing one functional group, multiple bonds and substituents.

(A) Lowest number for the functional group. 
Rule. 1. Select the longest continuous chain containing the carbon atom having the functional group. e.g.
 
Rule 2. The numbering of atoms in the parent chain is done in such a way that the lowest number must be always given to the functional group e.g.

Rule 3. All the rules for naming side chains as substituents are then followed as in the case of alkanes.

Rule 4. When a chain containing functional groups such as –CHO, – COOH, –COOR, – CONH₂, –COCl, –C ≡ N etc. is present it is always given number 1 and number l is usually omitted from the final name of the compound.


Rule 5. If the organic compound contains a functional group, multiple bond, side chain or substituent, the following order of preference should be followed:
Functional group > Double bond or Triple bond > Substituent/side chain, e.g.

Rule 6. If the compound contains two or more like groups, the numerical prefixes di, tri, tetra etc. are used and the terminal ‘e’ from the primary suffix is retained.