Chapter 21, Problem 86A

Interpretation Introduction

Interpretation:

The reason for use of numbers in the IUPAC name of unbranched alkenes and alkynes but not in the names of unbranched alkanes needs to be explained.

Concept introduction:

The hydrocarbon compounds contain compound that are made up of only hydrogen and carbon atoms. Hydrocarbon compounds that contains multiple bond(s) are said to be unsaturated hydrocarbon. Compounds containing double bonds are said to be alkene whereas compounds containing triple bonds are said to be alkyne.

Explanation of Solution

The numbering in the IUPAC name of the molecule indicates the position of functional groups like double bond, triple bond, branched alkyl group as a substituent and other functional group.

For unbranched alkenes and alkynes, the numbering is used to indicate the position of double and triple bonds respectively in the compound. The numbering of the compound is done in such a way that double and triple bond possess lowest number in the chain. For example:

For unbranched alkanes, there is no need to assign numbering as the whole compound contains only single bonded compound. For example: