Chapter 21, Problem 60A

Interpretation Introduction

Interpretation:

The difference in determining the parent chain in naming of alkenefrom that of same alkane needs to be explained.

Concept introduction:

The hydrocarbon compounds contain compound that are made up of only hydrogen and carbon atoms.

Explanation of Solution

The hydrocarbon compounds that contains single bond(s) between carbon atom(s) are said to be saturated hydrocarbon whereashydrocarbon compounds that contains multiple bond(s) between carbon atom(s) are said to be unsaturated hydrocarbon. Compounds containing single bonds are said to be alkane and compounds containing double bonds are said to be alkene.

The general formula of:

• Alkane is ${\text{C}}_{\text{n}}{\text{H}}_{\text{2n+2}}$ .
• Alkene is ${\text{C}}_{\text{n}}{\text{H}}_{\text{2n}}$ .

The number of H atoms in alkene is 2 units less than that in alkane.

In order to give the name to the organic molecules following steps are followed:

1. The parent (longest) continuous carbon chain is identified.

2. Name should be written in alphabetical order and numbering should be done in such a way that the substituent group gets lowest number.

3. Hyphen is used to connect the number to the name.

So, for alkane the parent chain is continuous long carbon chain and for alkene, the longest carbon chain should include the double bond which gets the preference over single bonds present in the chain.

For example:

In alkane structure, the parent chain is of 6 carbon atoms having a methyl substituent at position 2 so, the name of the compound is 2-methylhexane.

In alkene structure, the parent chain is of 6 carbon atoms and the numbering of the chain starts from double bonded carbon atom having a methyl substituent at position 2 so, the name of the compound is 2-methylhex-1-ene