Use resonance structures to identify the areas of high and low el...

Question

Use resonance structures to identify the areas of high and low electron density in the following compounds: a. CH3C(=O)H

b. CH3C(=O)NH2

c. CH3C(=NH)H

Accepted Answer

Hey everyone. Let's solve this problem. It says draw the resonance structures of the following compounds. And mark the regions of high and low electron density. So let's mark the regions of high electron density in green. And we'll mark the ones with low electron density in yellow. So we're looking at the resonance structures and remember that resonance structures show where electrons like to hang out on the molecule. Right? So it shows the different areas that they are likely to be residing in. So let's draw out our compounds and then we can show how those electrons might move. So first we have acetone, that's a common organic compound. And I see carbon double bonded to an oxygen. Well, when I see a double bond, I know that resonance is likely going to be involved. And since oxygen is electro negative, those electrons can hang out on that oxygen atom. Don't forget your brackets. So that will look like this. Oxygen will have three lone pairs now instead of two. And will we have some formal charges here? I think so. So we know that carbon likes to have four electrons touching it. It has four valence electrons. And in this structure it has 123 electrons touching it. So that leaves it with a plus one formal charge. And oxygen likes to have six valence electrons touching it and it has +1234567. So oxygen will have a negative one charge. So as you might guess, carbon here since as a positive charge is a region of low electron density and oxygen with the negative charge will be our region of high electron density. That makes sense. Right, cool. So let's move on to the next structure. We have a church bonded to see double bonded to oxygen bonded to nitrogen with a hydrogen and a method group. Okay, so similar to a I see that double bond carbon, carbon to oxygen. So those electrons from the double bond can swing up onto that electro negative oxygen. And we will have a second residence form. That looks similar to compound A with the carbon and oxygen Because oxygen now will have three lone pairs carbon and then the rest stays the same. So just like a Now our carbon still has three sigma bonds. So it'll have a plus charge. And that oxygen has one sigma bond and three lone pairs. So it will have a negative charge. So again, carbon is the area of low electron density oxygen is an area of high electron density. And can we have any other resonance structures? We can because carbon has that positive charge. And right next door, is that lone pair on nitrogen. So those electrons are going to want to move towards the positive carbon negative always moving towards the positive charge. And that will form a third resonance structure that looks like this. Our oxygen is staying the same. And now we have a carbon double bonded to that nitrogen, so no more lone pair and formal charges. Well our oxygen didn't oxygen didn't change. So it's still going to have that negative charge. Carbon now has its octet full with four bonds and four electrons touching it. And nitrogen though nitrogen oops, we'll do it up here. Nitrogen likes to have five valence electrons and it has 1234 touching it. So nitrogen is going to have a plus one formal charge here. So in addition to the carbon, our nitrogen is also an area of low electron density and oxygen is still high electron density. Okay, last one We have two methyl groups coming off of a carbon double bond into a nitrogen with a lone pair in a methyl group. Okay, so I see a double bond next to a nitrogen with a lone pair. We know nitrogen is pretty electro negative and it's between these two carbons. So it's definitely gonna have a partial negative charge. So it will want to hold onto those electrons since it's electro negative. So we have a resonance structure that will look like this. So now the carbon is single bonded to the nitrogen and that double bond becomes that extra pi bond becomes a set of electrons on nitrogen and that's it for resonance structures. What about formal charges? Well, carbon now only has three electrons touching it. And like we set up here that will leave it with a positive formal charge, nitrogen likes to have five but it has 123456. So that will be a negative formal charge. So in this structure, nitrogen has the high electron density, and carbon has the positive charge or the low electron density. That's it for this problem, I hope this video is helpful, and thanks for watching.

Use resonance structures to identify the areas of high and low electron density in the following compounds: a. CH3C(=O)H b. CH3C(=O)NH2 c. CH3C(=NH)H

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Use resonance structures to identify the areas of high and low electron density in the following compounds: a. CH3C(=O)H
b. CH3C(=O)NH2
c. CH3C(=NH)H