Q15-53E - Organic Chemistry (Mcmurry)

Question

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

Step-by-Step Solution

Answer

Step1: 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.

Step 2: 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.

Step 3: 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: