1. for the following molecules (a) give the number of π -bonds present in the shown structures, (b) draw all…

1. for the following molecules (a) give the number of π -bonds present in the shown structures, (b) draw all the resonance structures that illustrate the atoms that can support the shown charge, and (c) circle the most stable resonance structure.

1. for the following molecules (a) give the number of π -bonds present in the shown structures, (b) draw all the resonance structures that illustrate the atoms that can support the shown charge, and (c) circle the most stable resonance structure.

Answer

Explanation:

Step1: Count π - bonds

Double bonds contain 1 π - bond. In the given molecule, there are 4 double bonds. So the number of π - bonds is 4.

Step2: Draw resonance structures

  1. First, move the lone - pair electrons and π - electrons to create resonance. The positive charge can be delocalized over the atoms with available lone pairs or π - systems. Start with the lone pair on the nitrogen atom and move the π - electrons in the ring and the carbon - oxygen double bonds.
  2. For the carbon - oxygen double bonds, the oxygen can donate its lone pair to form a new π - bond and move the existing π - bond electrons to create a resonance structure.
  3. For the aromatic ring, the π - electrons can be shifted to distribute the charge.

Step3: Determine the most stable resonance structure

The most stable resonance structure is the one with the positive charge on the most electropositive atom and with the maximum number of complete octets and the least separation of opposite charges. In this case, the resonance structure where the positive charge is delocalized over the aromatic ring and the carbon - oxygen double - bonded carbons while maintaining the aromaticity of the ring is relatively stable.

Answer:

(a) 4 (b) [Here you would need to draw the resonance structures, which is not possible to do in pure text. But the general process is as described above. You can use a chemical drawing software like ChemDraw to draw them.] (c) [Circle the most stable resonance structure among the ones drawn as per the above - mentioned stability criteria.]