Resonance structures for given molecules

Question

What are the possible resonance structures for each of the 3 molecules given in the image attached;

https://ibb.co/HGbx41K

Answer 1

Hi Greene,

Your test for resonance structures is to ask whether it is possible to draw equally good dot structures while switching the locations of single and double bonds. In resonance structures, the extra electrons are not located just in the shown bond but are "delocalized" throughout the bonding region. When drawing resonance structures, only electrons move from one diagram to the next; you do not break bonds between atoms.

For your three diagrams, here is where I find resonance structures:

a: Switch the double bond over to the left side and move the negative formal charge to the right. This ozone molecule is often used in textbooks as the paradigmatic example of resonance.

b: You can move the double bond inside the ring to instead connect to the "top" carbon, and also move the lone pair of electrons from the "top" carbon onto the carbon two away counter-clockwise.

c. The three double bonds inside the ring can move over one each, still alternating. This is a very common resonance structure found in benzene and "aromatic" molecules.

It's a lot easier to see all of this with pictures. Come join me on a lesson some time, and I will be happy to illustrate these ideas on a document camera.

Best wishes to you, Greene!