Predict the products of the following eliminations of vicinal dibromides with potassium iodide.

step 1 Hello everyone. Let us see the following question. So here is a question where there are sequenc

Predict the products of the following eliminations of...

Key Concepts

Anti-Periplanar Geometry

Anti-periplanar geometry in an E2 reaction refers to the required spatial arrangement in which the hydrogen atom being removed and the leaving group are positioned 180° apart within the same plane. This configuration allows for an effective overlap of orbitals during the transition state, making the elimination process more favorable and determining the stereochemistry of the product.

E2 Elimination Reaction

The E2 elimination reaction is a one-step, concerted mechanism in which a base abstracts a proton at the same time as a leaving group departs, leading to the formation of a double bond. This mechanism is stereospecific because the proton and leaving group must be aligned in an anti-periplanar geometry, which significantly influences the structure of the final elimination products.

Vicinal Dihalide Elimination

Elimination reactions of vicinal dihalides involve the removal of halogen atoms from adjacent carbon atoms, typically via successive E2 eliminations. This process often results in the formation of alkynes after two dehydrohalogenation steps, where the geometric constraints, such as the anti-periplanar requirement, play a crucial role in determining which elimination pathway is favored and what products are ultimately formed.

Transcript

0:00 Hello everyone.

00:01 Let us see the following question.

00:03 So here is a question where there are sequence of reagents given.

00:08 So we have to find out the last product.

00:10 So the mechanism we will have to directly go through.

00:16 So we'll see we have a cyclopentanone, okay, which is substituted with side chain alcohol.

00:27 First it has to be treated with ethylin glycol.

00:30 How do we write ethylaryl? ch2 2 times oh2 group on both the sides, okay? followed with hydrolysis.

00:40 Then it is further treated with colin's reagent, colin's reagent, which is a weak oxidizing agent, which is then further treated with ethyl, c2h5, mg, br, and then further hydrolysis, h plus and h2o we have to tell the final product in the sequence.

01:07 So let us go to the mechanism.

01:13 So in the mechanism i'm having cyclopentinone.

01:19 So there is double bond o and then there is oh.

01:24 When treated with the ethylene glycol, see ethyline glycol i'm going to write like this.

01:29 Ch2, ch2, oh and oh.

01:39 We have to remove one unit of water here.

01:42 So as we remove one unit of water here, this is going to condense.

01:47 So, basically, i am going to protect one of the ketone group.

01:51 Okay, see what we are going to do here.

01:54 So, this is going to be connected to oxygen, oxygen, ch2, ch2.

02:01 So, we got cyclic acetyl.

02:08 Cyclic, not acetyl, we can say that ketal because anyway this is going to be cyclical.