Propose a mechanism for the following reaction:

Name: Problem 49, Chapter 12: Organic Chemistry
Uploaded: 2020-08-04T19:13:22-08:00
Duration: 4 min 14 s
Channel: Madeline Currie
Description: Propose a mechanism for the following reaction:

Key Concepts

Mechanistic Steps

This concept involves breaking down an overall chemical reaction into individual, sequential stages that describe how reactants convert into products. Each step includes specific bond-making and bond-breaking events, and the complete mechanism provides a detailed rationale for the reaction process.

Arrow-Pushing Formalism

Arrow-pushing is the tool used to illustrate the movement of electrons during a chemical reaction. By using curved arrows to show electron flow from nucleophilic centers to electrophilic sites, one can graphically represent the process of bond breaking and bond formation for a clearer understanding of the mechanism.

Reaction Intermediates

These are transient species that form temporarily during a reaction pathway, often influencing the reaction's course. Identifying and understanding intermediates is crucial, as they can help explain the stability and reactivity observed throughout the transformation.

Transition States

The transition state represents a high-energy, fleeting configuration of atoms at the peak of the reaction energy barrier. Although these states cannot be isolated, considering their structure and energy is essential for understanding the reaction rate and the overall energy profile of the mechanism.

Kinetic versus Thermodynamic Control

This concept addresses whether a reaction is governed by the speed of product formation (kinetic control) or by the overall energy stability of the products (thermodynamic control). Recognizing these factors is important when proposing a mechanism, as they influence which intermediates form and which reaction pathways are favored.

Transcript

00:01 This problem asks us to propose a mechanism for this reaction.

00:05 So we will start with an initiation step with our peroxide that will give us two ro radicals.

00:14 And then we'll take one of those ro radicals with this hccl3, trichloromethane, and pull the h off of it.

00:23 So we will end up with an alcohol left over from the ro and a methyl radical there, trichloronethyl.

00:32 Myzel radical.

00:34 Then we will take that ring structure.

00:37 This is an eight embered ring with two alkenes in it.

00:41 We'll take an h off of there.

00:44 We're using the allelic position because that is the most stable radical.

00:48 And we're going to use this radical that we've created to pull the h off of that ring and leave a radical behind.

00:55 So that will give us an intermediate that looks like this.

01:00 And then because this is an eight membered ring, there's some angle string going on there.

01:04 It's not the most stable or the most favorable confirmation so instead we are going to use this radical to first we're going to resonate it um move it over uh two carbons to get another intermediate that looks like this oops so now our radical is over here and now this will allow us to um make this into two conjoined five membered rings instead of an eight membered ring which is a lot more stable.

01:42 So what we'll do is we'll take the radical and one of the electrons from that double bond on the bottom and use that to make a new bond in between those two carbons and we'll leave a radical behind on that one.

01:57 So then we will get our five, two five -membered rings, which will look like this...

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