Chapter 20, Problem 6STP

Interpretation Introduction

Interpretation: The number of isomers in pentane needs to be determined.

Concept introduction: Isomers: These are the compounds having same formula but different arrangements of atoms and different properties.

Answer to Problem 6STP

Pentane have 3 isomers.

Explanation of Solution

The structure of pentane is $\begin{array}{l}\text{H}\text{H}\text{H}\text{H}\text{H}\\ \left|\right|\left|\right||\\ \text{H}-\text{C}-\text{C}-\text{C}-\text{C}-\text{C}-\text{H}\\ \left|\right|\left|\right||\\ \text{H}\text{H}\text{H}\text{H}\text{H}\end{array}$ and it can arranged in three different ways which results in different isomers with same formula but different arrangements of carbon and they possess different properties.

	Isomers	structure
1.	n-pentane	${\text{CH}}_3-{\text{CH}}_2-{\text{CH}}_2-{\text{CH}}_2-{\text{CH}}_3$
2.	2-methylbutane	$\begin{array}{l}{\text{CH}}_3-{\text{CH}}_2-\text{CH}-{\text{CH}}_3\\ |\\ {\text{CH}}_3\end{array}$
3.	dimethylpropane	$\begin{array}{l}C{\text{H}}_3\\ |\\ {\text{CH}}_3-\text{C}-{\text{CH}}_3\\ |\\ {\text{CH}}_3\end{array}$

Conclusion

All of these structures have five carbons in the chain with one carbon on the side