Do alkenes ever rearrange twice to get to the most stable carbocation?

[510586]

Alkenes rearrange in SN1 reactions or when adding HBr if a more stable carbocation is possible. But is it possible for a carbocation to rearrange twice (1 degree to 2 degree to 3 degree) to get to the stablest carbocation? Or is that too many steps?

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[darknightzzz]

this is a pre dental aka admission/interview/acceptance and such sort.

almost nobody on here remember about the DAT and especially ochem carbocation stability during rearrangement or especially HBr addition.

you will be better at posting in DAT forum

 

[510586]

this is a pre dental aka admission/interview/acceptance and such sort.

almost nobody on here remember about the DAT and especially ochem carbocation stability during rearrangement or especially HBr addition.

you will be better at posting in DAT forum

Oh shoot thought I was on the correct forum my bad!

 

[pulltheleverkronk]

Alkenes rearrange in SN1 reactions or when adding HBr if a more stable carbocation is possible. But is it possible for a carbocation to rearrange twice (1 degree to 2 degree to 3 degree) to get to the stablest carbocation? Or is that too many steps?

This post reminded me of how glad I am to be done with the DAT... lol

 

[MRZ8]

Alkenes rearrange in SN1 reactions or when adding HBr if a more stable carbocation is possible. But is it possible for a carbocation to rearrange twice (1 degree to 2 degree to 3 degree) to get to the stablest carbocation? Or is that too many steps?

It's possible. Multiple hydride shifts can happen and the positive charge keeps "jumping" towards the most stable adjacent carbon (with most hydrocarbon groups attached). Of course, there might be multiple products, the most stable of which predominates.

 

[510586]

It's possible. Multiple hydride shifts can happen and the positive charge keeps "jumping" towards the most stable adjacent carbon (with most hydrocarbon groups attached). Of course, there might be multiple products, the most stable of which predominates.

I have a dat destroyer question that only rearranges once. I remember a tutor said that it only rearranges once as well since 2 steps take longer or something but I might be wrong. I'll post an example to the thread on discussions or here if no one replies lol

 

[pulltheleverkronk]

It's possible. Multiple hydride shifts can happen and the positive charge keeps "jumping" towards the most stable adjacent carbon (with most hydrocarbon groups attached). Of course, there might be multiple products, the most stable of which predominates.

It's possible, but unlikely... normally if the shift is farther than one away, it won't happen. It would require too much energy. I doubt the DAT would test something like that. Although it's totally fair game to assume that if something is SN1, you know whether it's supposed to rearrange or not.

 

[MRZ8]

I have a dat destroyer question that only rearranges once. I remember a tutor said that it only rearranges once as well since 2 steps take longer or something but I might be wrong. I'll post an example to the thread on discussions or here if no one replies lol

What I said earlier was based on my orgo prof.."keep doin those hydride shifts." You might be right: 2 steps takes longer. But the product's more stable...meaning it should be energetically favorable (right?).

 

[510586]

It's possible, but unlikely... normally if the shift is farther than one away, it won't happen. It would require too much energy. I doubt the DAT would test something like that. Although it's totally fair game to assume that if something is SN1, you know whether it's supposed to rearrange or not.

Oh yea I got that part I think. I hate the feeling where you kind of know the basics and it starts to be more about finding weird exceptions to stuff -__-

 

[510586]

What I said earlier was based on my orgo prof.."keep doin those hydride shifts." You might be right: 2 steps takes longer. But the product's more stable...meaning it should be energetically favorable (right?).

Yea the reaction I have is like a naphthalene with a cyclohexene next to it. No idea if this is some strange exception but it can potentially place the Cl between the 2 rings. It would have a more stable carbocation but would be less stable by zaitsevs? augh

 

[kerfufle]

I got a 26 on the DAT ochem section last year and legitimately don't understand anything that is being talked about here. It didn't make sense when I took the DAT either but the power of memorization I guess..

 

[pulltheleverkronk]

I got a 26 on the DAT ochem section last year and legitimately don't understand anything that is being talked about here. It didn't make sense when I took the DAT either but the power of memorization I guess..

dying lol I feel this so hard