Chapter 1, Problem 1.82P

Interpretation Introduction

(a)

Interpretation:

All resonance contributors for the given ion are to be drawn using curved arrows to indicate which pairs of electrons are being shifted.

Concept introduction:

Resonance structure exists in species for which there are two or more valid Lewis structures. Resonance structures are imaginary whereas true species which is shown by the resonance hybrid. Resonance structures have different placement of their valence electrons but not their atoms. Resonance structures with greater number of atoms having a complete octet, more covalent bonds, and fewer atoms having a non-zero formal charge are considered to be stable. Resonance structures are drawn using curved arrows. A curved arrow shows how the electron pair moves. A curved arrow originates from a lone pair of electrons or from a covalent double or triple bond to indicate the specific pair of electrons that are being moved. The arrow points to an atom if the electrons being moved become a lone pair. Otherwise, the arrow points to the center of an existing bond to represent the formation of a new double/triple bond. A resonance structure can be drawn if a lone pair of electrons on an atom is adjacent to multiple bonds, or an incomplete octet on an atom is adjacent to multiple bonds, or there is a ring of alternating single and multiple bonds.

Interpretation Introduction

(b)

Interpretation:

Resonance hybrid for the given anion is to be drawn.

Concept introduction:

For a species, each valid Lewis structure is called a ‘resonance structure’ or a ‘resonance contributor’. A resonance hybrid is a weighted average of all resonance contributors. A partial bond is represented in a resonance hybrid by a dashed line connecting the two atoms. In the resonance hybrid, partial bonds are shown which represent the atoms over which the electrons are being delocalized.

Interpretation Introduction

(c)

Interpretation:

The longest $\text{C-C}$ bond for the given ion is to be identified.

Concept introduction:

For a species, each valid Lewis structure is called a ‘resonance structure’ or a ‘resonance contributor’. A resonance hybrid is a weighted average of all resonance contributors. A partial bond is represented in a resonance hybrid by a dashed line connecting the two atoms. In the resonance hybrid, partial bonds are shown which represent the atoms over which the electrons are being delocalized. The atoms involved in the delocalization of electrons gets a partial double bond character and thus have a shorter bond length than $\text{C-C}$ single bond.