Chapter 19, Problem 19.5P

Interpretation Introduction

Interpretation:

Using $\text{oxirane}$ as the only source of carbon, $\text{phenylbutan}-\text{1}-\text{ol}$ is to be synthesized from $\text{bromobenzene}$.

Concept introduction:

Our only source of carbon $\text{oxirane}$ contains two $\text{C-}$ atoms, and the product contains 10 $\text{C-}$ atoms, so two $\text{C-C}$ bonds must be formed. A $\text{C-C}$ bond-forming reaction would be difficult to carry out directly between $\text{oxirane}$ and $\text{bromobenzene}$, because such a reaction would entail the formation of a bond between two carbon atoms bearing a partial positive charge. The precursor should bear a carbon atom with negative or partial negative charge. One way to form a bond between two carbons of like charge is to carry out a separate reaction that first reverses the charge (or polarity) at one of the carbons. Thus, one carbon atom would become electron rich while the other would remain electron poor. This general idea of reversing a charge at a particular atom, called umpolung (a German term meaning “polarity reversal”), is a common practice in organic synthesis.