Draw the indicated number of resonance forms for each of the...

Key Concepts

Conjugation and Aromaticity

Conjugation involves a system of connected p orbitals where electrons can delocalize across adjacent bonds, enhancing molecular stability. In aromatic systems, such as those found in benzoate anions, the overlapping of p orbitals in the ring further stabilizes the ion by allowing the negative charge to be evenly distributed around the aromatic ring.

Formal Charge Distribution

In resonance theory, proper distribution and minimization of formal charges are vital in assessing the relative stability of each resonance contributor. Ensuring that the charges are placed on the most electronegative atoms and that overall charge separation is minimized makes the resonance forms more representative of the true structure.

Resonance Structures

Resonance structures are different Lewis structures for the same molecule or ion that differ only in the placement of electrons, not the arrangement of atoms. This concept is crucial in illustrating how electron density is spread over a molecule, increasing its overall stability.

Electron Delocalization

Electron delocalization refers to the spreading of electrons, especially those in ? systems or lone pairs, over several adjacent atoms. This dispersion of electron density helps stabilize the molecule or ion by lowering its energy.

Transcript

00:01 They want us to draw the indicated number of resonance forms for each of the following species.

00:06 So for this first one here, they want us to draw three resin structures.

00:09 So let's just go ahead and first draw the backbone.

00:17 So this we should have the phosphorus in the middle.

00:24 And actually, the way you would really draw this is so we have this carbon over here.

00:28 It has three hydrogens attached.

00:30 So hydrogen, hydrogen, hydrogen.

00:34 Then we have this oxygen attached to it, and then we're going to have phosphorus, or actually we're going to have three other phosphorus attached to it.

00:48 Now, we would need to go through and draw the lewis structure like we normally would, but just to save a little bit of time, this is going to look like this.

01:05 So negative, negative.

01:08 And if you were to double check, you would see that we would have the correct amount of loan pairs and everything for everywhere.

01:16 So we want to draw three brush and structure.

01:18 So we have one already.

01:19 So what's another one we could possibly draw? well, why don't we pop this double bond up and then pop that double bond down? so doing that would give us...

01:36 Actually, let me scoot this over a little bit first.

01:39 So doing that is going to give...

01:42 So i'm just going to draw this in the bond line as opposed to having draw those hydrogens out every time.

01:46 So it's just going to be...

01:50 Oh, with the two bonds there.

01:53 So the only thing we're moving is this section right here, so everything else stays the same.

02:05 So that oxygen that's going up, well, it had a double bond, but now it's a single bond.

02:11 And it had two lone pairs, but now it should have an extra one.

02:16 So it has three.

02:17 So it was positively charged, but it essentially gained an extra electron since it was already sharing one from that pie bond.

02:24 So now that's going to be negatively charged.

02:27 And then over here, this carbon was only with one.

02:34 Now it should have two double bonds.

02:39 And now that oxygen had to give away one of its own pairs.

02:43 So it would just have two long.

02:46 Pairs left and that negative charge would then become neutrally charged since we're essentially only giving away one electron since we're still sharing one of them.

02:56 So that's going to be one resident structure and then another resident structure that we could do would be to pop this bond we just formed back up and then kind of repeat and move that one down.

03:13 So just drawing the rest of this out.

03:18 So p then up here we have our negative charge.

03:25 This is going to go back to having a negative charge.

03:31 Because remember, we're moving one of the lone pairs back onto it.

03:38 So it essentially gained one electron.

03:41 And then this other carbon, well, it's gaining another bond, but it lost one of its loan pairs.

03:49 So it essentially gave up one electron to form that bond, so it should go to neutrally charged.

03:56 So this would be the three or at least three of the residence structures.

04:02 And if you wanted, we could actually get back to this one by moving this bond, not like that, back up to the oxygen and then moving one of those own pairs back, just to kind of complete the cycle.

04:16 Now for n .o3, or negatively charged n .03, they want us to go ahead and draw three of them.

04:27 So we're going to have our nitrogen, and then we're going to have three oxygens attached.

04:35 And if you were to go through the lewis structure to build it, that should end up giving us where one of the oxygens is going to be double bonded.

04:46 The other two, aren't and then the one that's double upon it has two loom pairs the one on the ends here that are not are going to have three loan pairs and then the nitrogen has no loan pairs so if you were to go through do the formal charge for this so this has negative negative and then that oxygen there is going to be neutrally charged now this nitrogen will notice it has essentially four electrons that it has, but nitrogen normally has five, so that means this is going to have a positive charge on it.

05:33 So we have one of our resin structures.

05:35 So now let's say if we can get another one.

05:39 Well, we can kind of repeat what we did over here for this phosphate ion.

05:45 So let's go ahead and first move this double bond towards our oxygen.

05:50 And then we can move this lone pair towards this bond here.

05:56 So doing that is going to give.

05:59 So let me just draw the skeleton out again really quickly.

06:02 So the oxygen on the right, we didn't do anything to.

06:05 So that's still just going to be negatively charged.

06:07 The oxygen on the bottom, well, it should be gaining a loan pair since we move that double bond to the oxygen.

06:15 So it has that negative charge there.

06:18 And then over here on the left side, it's giving away one of its own pairs, so it should have two, and then it has that double bond.