Chapter 10.5, Problem 8E

Interpretation Introduction

Interpretation:The manner a phase transfer catalyst can interact with $\text{HBr}$ via electrostatic, hydrogen bonding, dipole-dipole, and van der Waals interactions should be shown.

Concept introduction: Certain compounds facilitate the transfer of reagents within immiscible layers via the formation of ion pairs so as dissolve the polar parts of reagents and transfer them. These are called phase-transfer catalysts. This type of catalysis is known as heterogeneous catalysis.

The mode of action of such catalystis similar to a detergent that solubilizes the salts within the organic phase. For instance, the electrophilic addition of $\text{HBr}$ is facilitated when quaternary ammonium salts act as phase transfer catalysts via formation of certain “ion pairs”.

The major intermolecular interactions are classified as follows:

• Electrostatic or ionic that occurs primarily among positively charged cationic and anionic species.

• Hydrogen bondingthat occurs primarily among unshared electron pair of the electronegative atom and hydrogen-bonded to a strongly electronegative atom.

• Dipole-dipole occurs primarily between molecules that possess permanent dipoles. For instance interaction between two $\text{HBr}$ molecules.

• Van der Waals attraction occurs primarily within molecules in very close vicinity as these are the weakest.