Draw additional resonance structures for each species. |...

Name: Problem 43, Chapter 17: Organic Chemistry
Uploaded: 2019-11-19T04:14:12-08:00
Duration: 9 min 19 s
Channel: Ian Kaigh
Description: Draw additional resonance structures for each species.

Key Concepts

Conjugated Systems

Conjugated systems consist of alternating single and multiple bonds that allow for overlapping p-orbitals across adjacent atoms. This overlap facilitates electron delocalization, which is key in the formation and stabilization of resonance structures.

Formal Charge Distribution

Formal charge distribution involves assigning charges to atoms in a molecule based on the electron configurations suggested by Lewis structures. Analyzing formal charges helps determine the most stable resonance contributors and guides the placement of charges for optimal stability in resonance forms.

Electron Delocalization

Electron delocalization is the concept where electrons, particularly those in pi bonds or lone pairs, are spread over two or more adjacent atoms. This distribution leads to increased stability of the molecule by allowing charge and electron density to be shared rather than localized.

Resonance Hybrid

The resonance hybrid is a theoretical construct that represents the actual structure of a molecule as a weighted average of all its resonance contributors. It reflects the idea that the true electron distribution is more stable and often intermediate between the extremes depicted by individual resonance structures.

Resonance Structures

Resonance structures are different valid Lewis structures for the same molecule that depict alternative ways to arrange electrons. They illustrate the delocalization of electrons across two or more atoms, showing alternate possible distributions of bonding electrons and formal charges.

Transcript

00:03 This is the answer to chapter 17, problem number 43 from the smith organic chemistry textbook.

00:11 This problem asks us to draw additional resonance structures for each of these molecules.

00:19 And so remember, we're going to do this by just moving electrons, whether it's lone pairs or double bonds or both.

00:29 And so for a here, we can just move the electrons in our double bond.

00:38 I guess i could have drawn that first one bigger.

00:41 I'll draw the next two bigger.

00:43 So that's going to put the double bond there, and it's going to put the radical here.

00:51 And of course, technically these are all the same structure because all of these these carbons are really the same.

00:59 You know, there's nothing to distinguish any of these carbons.

01:03 But if any of them had substituents, it would be different.

01:12 But really, if you want to be technical, these are all the same structure.

01:16 And then we can just move the double bond like that.

01:22 That's going to put our radical there and our double bond here.

01:27 Okay.

01:28 And so that's it for a.

01:30 So b is pyrol.

01:33 And so this is actually going to be like two different sets.

01:38 So the first thing that we can do is move our lone pair of electrons to here and move our double bond.

01:48 Oops.

01:50 It's important to draw the arrows exactly where you mean them to go.

01:53 So our double bond, the electrons are going to go to that carbon.

01:57 So the way that i had drawn it at first would have been.

02:01 Indicating that we were making a new double bond.

02:06 And of course, that's not the case.

02:11 Okay.

02:13 So we're going to have a positive charge on our nitrogen now.

02:20 And double bond there.

02:22 And this carbon will have a loan pair and a negative charge.

02:28 Okay.

02:29 And so we can move the electrons again so we can move these here and these will go here and so now we have a double bond here we'll have a double bond here our nitrogen still has a positive charge on it and our loan pair and negative charge are now on that carbon okay so we can also do the same thing the other way so again starting from pyrol.

03:19 Oops, i forgot my double bonds...

Please give Ace some feedback