Chapter 7, Problem 7.47P

Interpretation Introduction

(a)

Interpretation:

For each step of the given unimolecular elimination $\text{(E1)}$ reaction, all electron-rich sites and electron-poor sites are to be identified.

Concept introduction:

An atom with partial or full negative charge is called an electron-rich site whereas an atom with partial or full positive charge is called an electron-poor site. An electron-rich atom has a lone pair of electrons whereas an electron-poor atom lacks an octet. In an elementary step, electrons tend to flow from an electron-rich site to an electron-poor site.

Interpretation Introduction

(b)

Interpretation:

Appropriate curved arrows are to be drawn to show the bond formation and bond breaking that occur in each step of the given unimolecular elimination $\text{(E1)}$ reaction.

Concept introduction:

In an elementary step, electrons tend to flow from an electron-rich site to an electron-poor site. In the first step of unimolecular elimination $\text{(E1)}$ reaction, one curved arrow is drawn from the lone pair of an electron-rich atom to the H attached to the electron poor atom. In the second step, one curved arrow is drawn starting from the middle of the broken bond to the atom on which the lone pair ends up, to indicate the departure of the leaving group. In the third step, one curved arrow is drawn from the negatively charged (electron-rich) atom in the base to the hydrogen in the substrate, and a second curved arrow is then drawn from the $\text{C-H}$ bond to the bonding region between the two C atoms by which the electron-poor C atom gains a share of electrons from the $\text{C-H}$ bond.

Interpretation Introduction

(c)

Interpretation:

Each step of the given unimolecular elimination $\text{(E1)}$ reaction is to be named.

Concept introduction:

An elementary step in which a proton is transferred from an electron-poor site to an electron-rich site and one bond is broken and another is formed simultaneously is called the proton transfer step. An elementary step in which only single bond is broken is called the heterolysis step.