Alcohols-2

Objectives of the Lesson

• To learn IUPAC naming rules of alcohols

• To be able to give the names of alcohols

​The following procedure should be followed to name alcohols according to the IUPAC system.

1. Select the longest continuous carbon chain to which the hydroxyl group is attached. Change the name of the alkane corresponding to this chain by dropping the final –e and adding the suffix –ol.

2. Number the carbon atoms in the longest continuous carbon chain starting from the end nearest to the hydroxyl group.

3. The carbon atom bearing the hydroxyl group takes the lowest number. Indicate the position of the hydroxyl group by using this number; indicate the position of other substituents (as prefixes) by using the numbers corresponding to their positions along the carbon chain.

​4. For straight chained compounds,

• if the -OH is attached to the first carbon, instead of number “1”, the letter “n”, meaning normal, can be used.

• If the -OH group is attached to an unsaturated hydrocarbon chain, the number of the carbon bearing the -OH group is substituted between the name of hydrocarbon and the suffix –ol.

• If the -OH group is attached to the first carbon of the unsaturated hydrocarbon chain, the number of the carbon bearing the -OH group is not written.

​5. If the -OH group is in the middle of the chain, the numbering of the carbon atoms starts at the end nearest any branching.

​6. If there are more than one OH group, “di, tri, tetra....” are used before the suffix –ol. The numbers of the carbon atoms bearing -OH groups are written before the name of the alcohol.