Organic Chemistry / Resonance Structures-1
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Solution: Draw all significant resonance structures for each of the fo...

Question

Draw all significant resonance structures for each of the following  compounds:

Video Transcript

Alright guys, let's see how many resonance structures you guys came up with. So, first, let's draw in our molecule again, we have an N, H, this six membered ring here and OH and then our positive charge right there. So, how many resonance structures that you guys come up with, let's first draw in our lone pairs, this nitrogen has a lone pair, this oxygen up here has a lone pair as well, so we can start from either the oxygen or the nitrogen, I'm just going to start with the oxygen because notice we can take one of these lone pairs, bring it down and make that lone pair turn into a PI bond, so what we would get, a resulting resonance structure, a valid one would look like this, where we have an H. Notice that we still have a lone pair there but now let's actually show that we have an OH, this lone pair is the same but now I'm going to draw in our bond here in black and resulting from that we actually get a positive charge at the top of here, okay? So this is one resonance structure. Now, from here can we draw any more? Well, remember in the beginning we could resonate, right? Because we had lone pairs adjacent to our positive charge and here take a look, we have a lone pair adjacent to our PI bond, so what we can show here, I'm going to show in red, we're actually going to make a PI bond, break a bond. So, our last resonance contributor, right? Our third one is going to look something like this and let's draw it again in blue, the last one is going to look like this, we have an N, we still have an H but now do we have a lone pair there? no, right? We're going to have a positive charge and now notice what we did is now do we have a PI bond here? well no, because now we actually made a bond like this, sorry guys. So, take a look, we made a bond here and in doing so we broke this PI bond, so that was just a stable bond and we now kick the electrons back to our O, so I'm going to draw here in black our new electrons, alright? and if we do this you'll see that what we get is these three resonance structures, okay? So, all we did starting from the first one is we pick somewhere to start drawing our resonance structure, I picked the oxygen but if you pick the nitrogen you get to the same product, right? You get the same three resonance structures, we brought the lone pair down and made a PI bond then we went on to the next resonance structure, so the one in the middle, right? From there what we did is we took the lone pair from the nitrogen, made a bond, broke a bond, so these are three resonance structures we get and hopefully you guys at home came up with the same ones. Alright guys. Now, let's take a look at your next question.