a. Draw resonance contributors for the following species. Do n...

Question

a. Draw resonance contributors for the following species. Do not include structures that are so unstable that their contributions to the resonance hybrid would be negligible. Indicate which are major contributors and which are minor contributors to the resonance hybrid.
b. Do any of the species have resonance contributors that all contribute equally to the resonance hybrid?
7.

b. Do any of the species have resonance contributors that all contribute equally to the resonance hybrid?

7. Chemical structure illustrating resonance contributors with a positive charge, highlighting major and minor contributors.

Accepted Answer

Hey there everyone, let's do this problem and says draw the significant resonance contributors for the compound given below indicate which components are major and which are minor contributors. Are there any major resonance contributors which contribute equally to the resonance hybrid? So let's review some rules about drawing resonance forms. I know residents can seem kind of intimidating at first. But the first rule is simply draw the Lewis compound for the structure and that will be your first resonance form. Alright. The next we want to move some electrons, right? We know that much. So we're only going to move pi electrons or lone pairs. Okay. We're never moving sigma electrons or single bonds and we're never moving atoms. Okay. We're not creating any ice members just moving electrons. And where do those electrons move to? Will they move towards Sp Adams and SP two Atoms Never Sp three Atoms. So I always like to see if there's a charge next to a double bond. That's the most common you'll see in these types of problems. And lastly, we're just moving electrons not adding or subtracting electrons. So the total number of electrons never changes and neither does the net charge okay total number of electrons net charge never changes. And anything else in this problem, it also asked about major and minor resonance contributors. So how do we know which one's major and minor? Well, that means a major contributor will be more stable, right. So the more stable a structure is the more that compound is going to hang out in that form. So let's look at some factors that impact stability. We can look at the octet of the atoms. If the octet is incomplete for some atoms that will make it less stable, we also can look at the atoms that have the charges and we look at their electro negativity. So if an electro negative atom, which we know likes to have electrons, if that atom has a positive charge, that will make it less stable and vice versa. If the charges are separated across a compound that will make it less stable. And lastly, we can look at our carbo cat ions if our car boot cat iron is on a less substituted Adam, that will make it less stable, right, more substitution, more stability. Alright. So let's draw our possible resonance contributors for this structure, which is our trope ilium cat ion. That's the name of this. Let me write that it's definitely good to know this cat on especially when you're talking about mass spectrometry. So I made this little template for our seven member ring because it is so difficult to draw a seven member ID ring have not mastered that yet. So we're starting with our bonds like so our positive charge at the top and we said that we want to look at a charge next to a pi bond, right? So our electrons are always going to move towards the positive charge, right. So we're basically just going to shift this these double bonds all the way around the ring until we get a structure until we get all the possible structures. and since our ring has seven carbons, that will mean that it can go around the ring twice. So now we move these pi electrons towards towards the positive charge. So the positive charge is always moving to where those electrons are coming from, right, the end of that double bond that you moved. So now moving this one down, which means our positive charges moving counterclockwise, right, 1 2 carbons away, two carbons away pi electrons are moving clockwise charges moving counterclockwise. I think when you're drawing a resonance structure, it's usually easiest to draw what is not changing first. So in this structure, we're moving our double bond clockwise. So we're not moving these other two bonds. So let's draw those first. And then that helps us see where our new bonds and charges are going. And we have one more structure that we can do. So we have each residents form where the charges on a different carbon. So since there are seven carbons in our ring. How many resonance structures do we have 7? Right? Because in each one that positive charges moving to a different carbon, right. So these are our seven resonance structures. And the problem asked, are there any major resonance contributors which contribute equally to the resonance hybrid? Well, this whole compound has all the resonance structures I should say has a positive charge on a carbon. The octet is the same for all the atoms. There's only one charge. So there's no separation of charges and all the carbons are substituted in the same way. So all of these structures are actually equal. So the answer is yes, all resonance, our major resonance as they contribute equally to the resonance hybrid to the resonance hybrid. So that makes c the correct answer for this problem. That's it for this one. I hope this video is helpful and thanks for watching.

Key Concepts

Resonance Structures

Major and Minor Contributors

Equally Contributing Resonance Structures

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