Draw the product by following the curved arrows. This...

Draw the product by following the curved arrows. This reaction is an example of a [3,3] sigmatropic rearrangement, as we will learn in Chapter 27. a. What carbon radical is formed by homolysis of the C- H$_a$ bond in propylbenzene? Draw all reasonable resonance structures for this radical. b. What carbon radical is formed by homolysis of the C- H$_b$ bond in propylbenzene? Draw all reasonable resonance structures for this radical. c. The bond dissociation energy of one of the C- H bonds is considerably less than the bond dissociation energy of the other. Which C- H bond is weaker? Offer an explanation.

Draw the product by following the curved arrows. This reaction is an example of a [3,3] sigmatropic rearrangement, as we will learn in Chapter 27.
a. What carbon radical is formed by homolysis of the C- H$_a$ bond in propylbenzene? Draw all
reasonable resonance structures for this radical.
b. What carbon radical is formed by homolysis of the C- H$_b$ bond in propylbenzene? Draw all
reasonable resonance structures for this radical.
c. The bond dissociation energy of one of the C- H bonds is considerably less than the bond
dissociation energy of the other. Which C- H bond is weaker? Offer an explanation.

Transcript

0:00 Hello everyone.

00:01 Today we're doing one of the challenging problems, problem 54 of chapter 6, and this gives us a propobenzene structure and asks us to determine the carbon radical formed from homolysis of a ch bond, particularly a cha bond, so this one right here, and draw all the reasonable resonance structures for this radical.

00:24 So let's go ahead and do that.

00:25 So if i'm doing a homolytic cleavage, i know that it's going to be an equal split of these two electrons in the sigma bond, one to my hydrogen atom, one to my carbon.

00:39 So that's going to form my radical.

00:48 So i have my carbon radical here and then my proton radical here, which is just a spectator at this point.

00:58 So now it's asking for me to draw all possible and all reasonable resonant structures.

01:06 So let's go ahead and draw some resident structures.

01:09 So this is one resident structure.

01:11 Another one is that we can actually form a new pie bond here with this radical donating in.

01:16 And one of these pie bond electrons donating in.

01:20 And then the other electron will go to this carbon here.

01:24 Remember, in order to draw your resonant structures, you need to draw double -headed curly arrows.

01:31 Sorry, double -headed arrows.

01:32 So this indicates it's a resonant structure.

01:35 Now i'm just going to redraw my structure so i have a new double bond here a radical here and then i have those two bonds still here this is one radical one resident structure but again i can form a new sigma bond here and using one of those electrons from the radical one electron from my pie bond and form a new radical over there on the carbon and now i have this new sigma bond, this new pi bond here, my original pi bond there, this pie bond here, and now i have my radical over here.

02:26 Once again, you know, you could work your way around the entire structure doing the same process, making a new pie bond, moving your radical over to the carbon, is directly adjacent to the far end of your original pie bond.

02:43 And now i have my original pie bond here, my original pie bond here, and now i've formed a new pie bond over here and the new radical here.

02:59 Lastly, i can form another resident structure with a new double bond here, double bond here, the double bond here, and the radical up here.

03:31 So as you see, we have one, two, three, four resonance structures here.

03:38 So b asks us, what carbon radicals is formed when homolysis occurs on a c -h -b bond? draw all the reasonable resonance structures.

03:47 So let's draw our radical being formed from the c -b bond...

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