Chapter 20, Problem 6A

Interpretation Introduction

Interpretation: The reason for propane and butane with unbranched chained to not be straight and the bond angle between the carbon atoms of propane and butane needs to be determined.

Concept introduction: Saturated hydrocarbons are called alkanes.

Answer to Problem 6A

Unbranched chains of propane and butane is not really straight because of the tetrahedral geometry and the bonding angle between carbon atoms is $\text{109}\text{.5°}$ .

Explanation of Solution

The two members are propane, with three carbonatoms and the formula ${\text{C}}_{\text{3}}{\text{H}}_{\text{8}}$ , and butane, with four carbon atoms and the formula ${\text{C}}_4{\text{H}}_{10}$ . Again, these are saturated hydrocarbons (alkanes); each carbon is bonded to four atoms.Alkanes in which the carbon atoms form long “strings” or chains are called normal, straight-chain, or unbranched hydrocarbons.

The chains in normal alkanes are not really straight but zigzag, because the tetrahedral angle is $\text{109}\text{.5°}$ .

Conclusion

Each member of alkane is obtained from the previous alkane by insertion of a methylene, ${\text{CH}}_{\text{2}}$ , group