Propose a mechanism to account for the following reaction: (EQUATION CAN'T COPY)

Name: Problem 65, Chapter 16: Organic Chemistry
Uploaded: 2020-05-16T02:00:02-08:00
Duration: 8 min 30 s
Channel: Matthew Lueckheide
Description: Propose a mechanism to account for the following reaction: (EQUATION CAN'T COPY)

step 1 Okay, propose a mechanism for the following reaction. So let's just look at what we have here, r

Propose a mechanism to account for the following reaction:...

Key Concepts

Reaction Mechanism

A reaction mechanism is a step-by-step description of the sequence of elementary processes by which reactants are transformed into products. It details the bond making and breaking events, the formation of intermediates, and the corresponding transition states. Understanding the mechanism allows chemists to predict and rationalize the course of the reaction as well as its stereochemical and regiochemical outcomes.

Electron Pushing Formalism

Electron pushing formalism uses curved arrows to visualize the movement of electrons during a chemical reaction. This graphical method is essential for demonstrating how bonds are broken and formed, providing insight into the flow of electron density which aids in constructing a plausible sequence of mechanistic events.

Reaction Intermediates

Reaction intermediates are transient species that form during the conversion of reactants into products. They may include cations, anions, radicals, or neutral molecules and are not isolated under normal reaction conditions. Identifying and characterizing these intermediates helps elucidate the underlying mechanism and determine the energetic profile of the reaction pathway.

Transition States

Transition states are high-energy configurations that occur transiently during the conversion of one intermediate species to another. They represent the peak of the energy barrier along the reaction coordinate. Understanding the nature of the transition state is vital for evaluating the kinetics of each reaction step and the overall reaction rate.

Rate-Determining Step

The rate-determining step is the slowest step in the reaction mechanism, which effectively controls the overall reaction rate. Identifying this step provides crucial insights into the kinetics of the reaction and helps in predicting how changes in conditions or substrates might affect the reaction's course.

Transcript

00:01 Okay, propose a mechanism for the following reaction.

00:05 So let's just look at what we have here, right? so the reagent is aluminum chloride, which implies that it's going to be doing some kind of, some kind of fridial crafts potentially, right? we don't have any other reagents, so it looks like it's going to be intramolecular.

00:27 And you form a carbon -carbon bond.

00:30 Right.

00:31 So your carbon -carbon bond is being formed ortho to this alcohol group and meta to this acal group, which fits the directing properties of alcohol and acal groups.

00:45 And you just have to identify where your alcohol chloride is.

00:49 In this case, it's actually tethered to your molecule.

00:55 Right.

00:55 So when it comes to these, so let's say that you weren't.

01:00 Given the product, right? these types of cyclizations are favored when you can make five, six, and rarely seven membered rings, right? so you could recognize that if you're thinking about being able to cyclize at this position, you'll be able to form a one, two, three, four, five, ignore the chlorine because that's going to be your leaving group, membered ring.

01:23 So eventually you're going to have a bond between this carbon and that carbon to make a five membered ring.

01:37 So why don't we arrow push and we'll see if that is what actually happens.

01:42 Right.

01:46 So we can start by redrawing the molecule.

02:10 Why am i in red? okay.

02:17 Right.

02:17 But is that the first step in freedom of graphs? it is not.

02:20 So why am i doing that? so let's use your alcohol highlight.

02:23 So for right now, i'm going to call it r.

02:26 I'm going to call this, basically, this entire thing, r.

02:30 So i'll just do the alchal chain.

02:33 So that's 1, 2, 3, 4 carbons long.

02:35 1, 2, 3, 4 carbons long.

02:38 1, 2, 3, 4, 5.

02:40 Boom.

02:41 1, 2, 3, 4.

02:42 Cl.

02:42 Great.

02:43 And that's going to attack the aluminum chloride to give us a activated 1, 2, 3, 4 cl.

03:02 And the reason why we can't do this is because the reason why we can't draw free carbocadion right away is because it would be primary, right? it would be there.

03:11 So here's the thing about frito crafts ' alcalations.

03:14 You know that rearrangements are possible.

03:16 So while i was talking before, you might have realized that i wasn't going to be drawing the right product, right? i was saying that you're going to make a bond from here to here, which is wrong.

03:29 Also, i didn't include that in my counting, right? so i didn't include the actual atom.

03:34 So if i did that, i would actually make a six -membered ring.

03:37 You'll notice that the new that's formed is between the ring and a secondary carbon, but the chloride's on a primary carbon.

03:46 So you have to think about rearrangements.

03:49 And then once you're done thinking about it, you have to do it with your arrow pushing.

03:53 Right.

03:54 So this, you're going to have a hydride shift, which will give you a secondary carbocadion, which i think you've done before in some of these practice problems.

04:03 Oops.

04:04 Right.

04:04 So what you're going to end up doing is, i'm going to scroll, beautiful scroll function.

04:10 You're going to have this hydride shift.

04:14 You know, just for clarity, i'm going to redraw.

04:17 One, two, three, four, c .l.

04:20 A .l.

04:21 Boom, boom, boom.

04:23 C .l.

04:24 C .l.

04:25 I forgot a positive charge here.

04:26 I just realized that when chlorine has two bonds, it's positive.