Question

Draw all of the resonance forms for each. What patterns emerge?

Short answer

Tropylium cation or cycloheptatrienyl cation is aromatic with six pi electrons and its molecular formula is${\left[{\mathbf{C}}_{\mathbf{7}}{\mathbf{H}}_{\mathbf{7}}\right]}^{\mathbf{+}}$and its molar mass is 91.132 g/mol.

Step-by-step solution

Tropylium cation

Tropylium cation or cycloheptatrienyl cation is aromatic with six pi electrons and its molecular formula is${\left[{\mathbf{C}}_{\mathbf{7}}{\mathbf{H}}_{\mathbf{7}}\right]}^{\mathbf{+}}$and its molar mass is 91.132 g/mol.

a) Resonating forms of tropylium cation

The resonating forms of the tropylium cation are shown as follows:

The resonating form of other analog is as shown:

The patterns show that alternating double bonds in an organic compound are delocalized to a considerable extent which makes their properties different from the isolated olefinic double bonds.

b) Resonating forms of pyrrole anion

The resonating form of pyrrole anion is as shown:

The resonating form of the liner analog is as follows: