Question

Organic chem

Answer 1

is there a better way (reagent) to get Hoffman regioselectivity?

Answer 2

Well, from what I remember in lab, it's really hard to control a reaction sometimes, which is why you almost never obtain 100% yield in an experiment. You can make a reaction proceed in a manner in which you obtain a high yield, for instance maybe 70% of the product above and 30% of the product below:

Actually, I think the product i drew is your major, because \(E1\) favors steric hindrance? Please correct me if i'm wrong. I always confuse \(S_n1\) with \(E1\).

Anyways, using the proper tools and instruments in a lab, you could probably obtain 70% major (or higher depending on your lab instruments and conditions), and about 30% minor (whether in crystal form or solution). So, you can come close. Especially since there is resonance going on in the intermediate step. I believe this is an \(E1\) reaction? So as you know, your first step is dettachment of the bromine, then resonance stabilization also plays a role in (hoffmann regioseletcitivy).

Speaking in terms of reagents, there are probably other reaction pathways that you could follow to get a higher yield of your major. Maybe use a metal catalyst? Or addding high concentrations? Again, it's hard to really control an reaction in organic chemistry. Especially in first year organic lab! Oh MAN.

Answer 3

For your particular problem, I think the other method i was htinking was halohydration because halohydration IS regioselective.

Answer 4

Thanks for a very thorough answer. I'll look into halohydration