Draw resonance contributors for each of the following species ...

Question

Draw resonance contributors for each of the following species and rank them in order of decreasing contribution to the resonance hybrid. Then draw the resonance hybrid.

d. Hexagonal ring structure with a double bond and an oxygen atom, illustrating resonance contributors and hybridization.

Accepted Answer

All right. Hi, everyone. So for this question, it's asking us to draw the resonance forms to the below given compound. Also draw the resident hybrid and indicate their relative contribution, contribution to the resident hybrid. And our starting material here is ZN methyl cyclo hex two in one. I. So first, let's go ahead and talk about resonance, right? Because recall really quickly that resonance refers to a de localization of electrons throughout a molecule. And that de localization increases the stability of the molecule overall. No the different ways in which electrons can de localize themselves around a molecule result in different resonance forms, right? And resonance forms or resonance structures are structures of the same compound that differ only in the placement of electrons. So when you go ahead and you combine all relevant resonance forms and you take an average of them, so to speak, you're kind of combining all different resonance forms together. That's how you end up with a resonance hybrid. And the thing is that resonance forms do not always contribute equally to the residents hybrid, right? Depending on the relative stability of one over another, you might see one resonance form have more of a contribution. So let's discuss that, right, like I mentioned a few seconds ago, right, the more stable a resonance form is the more it contributes to the resonance hybrid overall. So let's start with the molecule or the starting material that we have on the screen right now. The first step when it comes to drawing a resonance form is to draw the les structure of the compound that you see because that is actually one of the residence forms for the compound. So let's go ahead and do that right. So here I'm going to go ahead and draw the same molecule as it is on the screen. Except here, I want to highlight all electron pairs. So I'm going to go ahead and highlight the lone pair of electrons on nitrogen. And here it is right, I'm only going to move it downwards. So I have more space. So now let's go ahead and discuss the movement of electrons in resonance because here recall that Sigma bonds never change during a residence, right? The only electrons that are moving around during residence come from either lone pairs of electrons or pi electrons. And those electrons only move towards SP or SP two hybridized atoms only never towards an sp three hybridized atom. And also we have to take care to ensure the fact that all of our charges are staying the same for each resonance structure, right? The formal charge of a particular atom might change, but the overall charge of the molecule should not. So now let's go ahead and discuss what we see here, right? We have an all keen in between carbons two and three of the rate. Now those are pi electrons, right? And those pi electrons can go ahead and move around. So here, right, you'll notice that the keen and the I mean are in conjugation, which means that they're separated by exactly one sigma bond in between. So that sigma bond in between gives us the space, so to speak, for these electrons to move around. And that creates resonance because now the pie pod of my alkene can jump in between carbons one and two instead of between carbons two and three. And in the meantime, or as a result of that, the pi bond of the iine shifts upwards towards the nitrogen. And so that creates a resonance structure like soap. So right now I'm just going to draw my Sigma bond which do not change, right? But now my nitrogen has gained an additional loan pair of electrons. So that results in a negative charge there on nitrogen. And now there's a double bond in between carbons, one and two of the ring, which means that carbon three has a positive charge. So here we have the two residence forms because if we go ahead and we have nitrogen, donate its pair of electrons in between itself and carbon, we go ahead and we regenerate the first structure. So now let's talk about the resonance hybrid, right? And in the residence hybrid, I'm going to actually scroll down and draw. So in the resonance hybrid, the first thing I do once again is I go ahead and I draw my signal bonds because those don't change. So here's my nitrogen and here's my meth group. So now, right in a resonance hybrid, instead of showcasing my either my pie bonds or my loan pairs, you draw dash lines to showcase the region in which electrons are de localized in. Right. So in my resonance structure structures, I should say my pie bond extends all the way up to carbon three in the ring. So that's the starting point. And here in my second resonance structure, they extend upwards towards nitrogen which has a negative charge. So here I'm drawing a dash line between the nitrogen and carbon three to showcase that that is where my electrons are de localized in. That's the region of de localization. So now in my resonance hybrid, we also have to include partial charges. And since nitrogen has a negative charge in one of my resonance forms in my hybrid, it's going to have a partial negative and carbon three is going to have a partial positive because it was positively charged in one of my structures. So here is my resonance hybrid. So now let's talk about contribution of one resonance form to the hybrid because what you'll notice is that one of our resonance structures features a separation of charges. And the other one does not right, because notice how one the first resonance structure doesn't have any ions or an ions. But the second one does now recall that resonance structures that have separation of charges are actually less stable then their more neutral counterparts. So because of that right, the first resonance structure is going to be the major contributor because it is more stable, there is no separation of charges. So now here is your final answer. So just to recap right, resonance is a de localization of electrons throughout a molecule. And when you take the average, so to speak of all relevant resonance forms, you generate what's known as the resonance hybrid. But depending on the relative stability of one resonance form over another, they may not contribute equally to the resonance hybrid because the more stable a resonance form is the more it is going to contribute to the resonance hybrid compared to other forms. So I know that was a lot, but we made it to the end if you stuck around. Thank you so much for watching. And I hope you found this helpful.

Draw resonance contributors for each of the following species and rank them in order of decreasing contribution to the resonance hybrid. Then draw the resonance hybrid.
d.

Key Concepts

Resonance Structures

Resonance Hybrid

Stability of Resonance Contributors

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