Ochem Major Products

[justwu86]

---

Members do not see this ad.

Was working on achiever tonight...everytime they asked which would be the major product(s) for a electrophillic subsitution reaction on a benzene with a ortho/para directing group, they said substitution at both the Ortho and Para position would be major products. In my ochem class, I was taught that Ortho would be the predominant/major product due to steric hinderance...anybody what answer they'd expect on the actual DAT? Ortho or ortho and para.

thanks in advance.

 

[miedvied]

If your OP director is NH2, it'll be substituted at ortho and para as a major - NH2 is extremely activating, and you can't isolate the para product well.

If you have a less activating OP director (i.e., methoxy, or even a halogen), your major product will just be para, *especially* if the activator is bulky - that makes the ortho position even less attractive.

Your major is ortho-only only when the para position is already occupied by another group, or if there's a meta-director on the ring that gives double-reinforcement to the ortho site.

 

[thisisfjai]

In my ochem class, I was taught that Ortho would be the predominant/major product due to steric hinderance...

😵 what ochem class was this? but answer is what ^^ said

 

[justwu86]

Thanks for the reply, I knew certain groups were more activating than others but I never knew that the more activating produces at both ortho and para positions.

Sorry I meant my ochem class told me that PARA is the major product instead of ortho due to steric hinderance

I went back to achiever and looked at the question...both times CH3 was the activating group and both times the correct answer was a mixture of ORTHO and PARA. I know CH3 has little steric hinderance but it is not extremely activating either...I'm assuming steric hinderance plays a large role on direction then how strongly activating something is?

 

[justwu86]

anyone?

I'd just assume that anytime they ask for major products...ortho and para will be the answer when adding to a benzene ring with an activating group thats not to bulky..