Chapter 22, Problem 82A

a.

Interpretation Introduction

Interpretation: To give the isomerization reaction between pentane and 2-methyl butane.

Concept Introduction: A chemical process in which the compound is changed into different isomers is known as an isomerization reaction.

Answer to Problem 82A

The isomerization reaction between pentane and 2-methyl butane is shown as follows:

Explanation of Solution

Pentane and 2-methyl butane are structural isomers or they can be classified as chain isomers.

Pentane isomerizes into 2-methyl butane and 2,2-dimethyl propane.

The isomerization reaction can be depicted as follows:

  

b.

Interpretation Introduction

Interpretation: To give the type of isomers.

Concept Introduction: The isomers in which the arrangement of atoms is in a different order while the molecular formulas of the compound remain the same are known as structural isomers.

Answer to Problem 82A

Pentane and 2-methyl butane are chain isomers.

Explanation of Solution

In chain isomers, the molecular formula is the same for both compounds while how carbon chains are arranged is different.

Both pentane and 2-methyl butane have the same molecular formula that is ${\text{C}}_{\text{5}}{\text{H}}_{\text{12}}$ . Both are composed of five carbon atoms where pentane is a continuous carbon atom chain while 2-methyl butane is a four-membered carbon chain having a methyl substituent at the second carbon atom.

  

c.

Interpretation Introduction

Interpretation: To predict which isomer has the lowest boiling point.

Concept Introduction: The isomers in which the arrangement of atoms is in a different order while the molecular formulas of the compound remain the same are known as structural isomers.

Answer to Problem 82A

2-methyl butane has the lowest boiling point than pentane.

Explanation of Solution

The boiling point is the temperature at which the vapor pressure of the substance becomes identical to the pressure surrounding the liquid.

The boiling point decreases as the branching in the compound increases. Both pentane and 2-methyl butane are chain isomers of each other. In pentane, the carbon atoms are arranged in a straight-chain isomer while in 2-methyl butane the carbon atoms are arranged in branches.

Therefore, the boiling point of 2-methyl butane is less than pentane.