Draw all possible resonance structures for the following cation and indicate which structure mak

Draw all possible resonance structures for the following...

Key Concepts

Resonance Structures

Resonance structures are different valid Lewis structures of a molecule that depict the delocalization of electrons, particularly in systems with conjugated bonds or lone pairs. They are used to represent the electron distribution in a molecule, even though no single structure can fully describe its actual electronic state.

Resonance Hybrid

The resonance hybrid is the true representation of a molecule’s electron distribution, formed by the combination of all possible resonance structures. It reflects the delocalization of electrons across the entire molecule and gives a more accurate picture of its structure and stability.

Relative Stability of Resonance Contributors

The contribution of each resonance structure to the resonance hybrid depends on its relative stability. Structures that minimize formal charges, comply with the octet rule, and place charges on atoms with appropriate electronegativities contribute more significantly to the resonance hybrid than less favorable ones.

Cation Stabilization Through Resonance

In the context of cationic species, resonance can significantly stabilize the positive charge by delocalizing it over several atoms. The ability to spread the charge reduces local electron deficiency and increases overall molecular stability, making certain resonance forms more favorable.

Transcript

00:02 This is the answer to chapter 16, problem number seven from the smith organic chemistry textbook.

00:10 And this problem asks us to draw all possible resonance structures for the cation that we're given here and indicate which structure makes the largest contribution to the resonance hybrid.

00:22 Okay.

00:23 And so in order to draw resonant structures, we're going to move electrons around.

00:28 So the first one we can draw, we can just move the electrons of this double.

00:32 Bond over.

00:35 And so that is going to give us a resonance structure that looks like this.

00:53 So this double bond is still right here.

00:56 We now have a double bond there.

00:59 And our positive charge is going to be seated right there on that carbon.

01:04 Okay.

01:05 So our next possible resonance structure is going to be moving these electrons to here.

01:11 And so when we do that, we get to this.

01:17 Structure.

01:27 So here we go.

01:31 And our positive charge is now going to be on this carbon.

01:39 And so lastly, we can have one of the lone pairs from this oxygen, add in there.

01:47 And that is going to give us this resonant structure.

02:00 And so we now have a double bond here.

02:05 The oxygen is only going to have one lone pair on it, and it's going to have a positive charge.

02:12 And so, so, we now have a double bond here...

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