Chapter 21, Problem 88A

(a)

Interpretation Introduction

Interpretation:

Whether the name 2-ethyl-2-butene is correct or not needs to be determined and the structure of the compound should be drawn.

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.

Answer to Problem 88A

The name 2-ethyl-2-butene is wrong and the correct name will be 3-methyl-2-pentene and the structure of the compound is:

Explanation of Solution

The given name of compound is 2-ethyl-2-butene so, from the name it can be concluded that the parent chain contains 4 carbon atoms with a double bond at position 2 and an ethyl substituent at carbon 2. So, the structure of the compound will be:

Now, according to IUPAC rules of naming of organic compound the longest carbon chain should be the parent chain containing double bond and substituents at lowest number so the numbering will be:

Hence, the name 2-ethyl-2-butene is wrong and the correct name will be 3-methyl-2-pentene.

(b)

Interpretation Introduction

Interpretation:

Whether the name 1, 4-dimethylcyclohexene is correct or not needs to be determined and the structure of the compound should be drawn.

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.

Answer to Problem 88A

The name 1, 4-dimethylcyclohexene is correct and the structure of the compound is:

Explanation of Solution

The given name of compound is 1, 4-dimethylcyclohexene so, from the name it can be concluded that the parent chain contains 6 carbon atoms cyclic ring with a double bond at position 1 and two methyl substituents at carbon 1 and 4. So, the structure of the compound will be:

Now, according to IUPAC rules of naming of organic compound the longest carbon chain should be the parent chain containing double bond and substituents at lowest number so the numbering will be:

Hence, the name 1, 4-dimethylcyclohexene is correct.

(c)

Interpretation Introduction

Interpretation:

Whether the name 1, 5-dimethylbenzene is correct or not needs to be determined and the structure of the compound should be drawn.

Concept introduction:

Benzene is an aromatic compound with 6 carbon attached to each other in cyclic hexagonal ring. Each carbon is attached to1 hydrogen by single bond and one carbon with double bond on one side and single bond on other side.

Answer to Problem 88A

The name 1, 5-dimethylbenzene is wrong and the correct name will be 1, 3-dimethylbenzene and the structure of the compound is:

Explanation of Solution

The given name of compound is 1, 5-dimethylbenzene so, from the name it can be concluded that the parent chain is benzene cyclic ring and two methyl substituents at carbon 1 and 5. So, the structure of the compound will be:

Now, according to IUPAC rules of naming of organic compound the longest carbon chain should be the parent chain and substituents at lowest number so the numbering will be:

Hence, the name 1, 5-dimethylbenzene is wrong and the correct name will be 1, 3-dimethylbenzene.