Addition of HBr to which of the following alkenes will lead to a rearrangement? a. b. c.

Name: Problem 18, Chapter 10: Organic Chemistry
Uploaded: 2022-09-02T09:38:04-08:00
Duration: 3 min 50 s
Channel: Timothy Gailey
Description: Addition of HBr to which of the following alkenes will lead to a rearrangement? a. b. c.

Addition of HBr to which of the following alkenes will lead...

Key Concepts

Electrophilic Addition Mechanism

The electrophilic addition mechanism involves an electrophile attacking the electron-rich double bond of an alkene, leading to the formation of a carbocation intermediate followed by nucleophilic attack. This is the fundamental process behind many addition reactions to alkenes, including the reaction with HBr.

Carbocation Intermediate

A carbocation intermediate is formed after the initial protonation step in the electrophilic addition mechanism. The structure and stability of this intermediate are critical because a more stable carbocation is favored, guiding the overall outcome of the reaction.

Carbocation Rearrangement

Carbocation rearrangement refers to the process where an initially formed, less stable carbocation undergoes a structural shift (such as a hydride or alkyl shift) to form a more stable carbocation. This rearrangement can lead to unexpected products and is a key concept in understanding reaction pathways that involve intermediates.

Markovnikov's Rule

Markovnikov's rule predicts that during the addition of acids such as HBr to alkenes, the proton will add to the carbon with more hydrogen atoms, resulting in the formation of the more stable carbocation at the more substituted carbon. This rule helps explain the regioselectivity observed in many electrophilic addition reactions.

Transcript

00:01 Addition of hbr to which the following will lead to a rearrangement.

00:05 A rearrangement, of course, meaning a carbocation rearrangement.

00:09 So which one of these will create a carbocation, which carbototion can be stabilized by rearranging.

00:16 So let's do the simple.

00:18 And let us react with hbr in each of these.

00:22 So what happens? we have donation of electron there, donation of electron to the hydrogen.

00:29 Hydrogen gives to the br.

00:31 We then have that does, we lose our alken, we gain a new carbocat ion right there and we have a bond with a hydrogen right here which we will draw there just so we know it's there but we don't need to continue drawing it.

00:46 We now also have this negative br floating out looking for someone to hang out with.

00:54 Let's look at our carbokion.

00:56 Do we have the ability to rearrange? well, it looks like we could potentially rearrange here with one of these hydrogens.

01:07 Will we? no, we will not, because there's nothing to be gained here.

01:12 So there is a resonant structure going on here, but i wouldn't consider that grounds for rearrangement.

01:18 So in this case, there's no rearrangement.

01:21 This br will attack the carbocat on right here, just like that.

01:30 No rearrangement.

01:34 Looking at b, all right, react it with our hbr.

01:42 So we're going to donate in because it's more stable to donate in.

01:46 And then we will send this one out.

01:50 We'll donate to br...