It’s one point to learn about electrophilic aromatic substitution reaction of benzene itself. Yet once friend move past benzene, that’s as soon as things begin getting really interesting.

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Today we’ll describe the two main patterns whereby substituents “direct” electrophilic fragrant substitution. In one pattern, substituents direct the reaction to offer either the “ortho” (1,2) or “para” product, v a slight preference for “para” (1,4). In the second pattern, a various family the substituents direct the reaction to offer primarily the “meta” (1,3) product.

Table of Contents

1. Ortho-, para- Directors

Here’s a fascinating observation.

Start through a monosubstituted benzene. Then carry out some sort of electrophilic fragrant substitution (nitration, halogenation, sulfonylation – transforms out the doesn’t matter).

Two essential reaction patterns room observed. 

It’s crucial to note that these two patterns are wholly a role of the substituent and not the reaction itself.

In one pattern, ortho- and para– products dominate, and the meta- product is really minor byproduct.


What carry out we notice?

First: no activating groups are meta directors.Second: what’s up v the halogens?

Yes indeed. What is up through the halogens, and how is it that they deserve to be deactivating (i.e. Sluggish down the reaction rate) and yet lead to ortho-, para- products?

4. The an essential To expertise ortho-, para- Directors And meta- director Is To recognize The security of The Carbocation Intermediate

There’s no quick and thoroughly answer to these questions, and also it’s precious its very own separate blog short article for the reason.

However, the first place come start is the it has to do with the stability of the carbocation intermediate in electrophilic fragrant substitution reactions. an ext specifically, exactly how does every substituent impact the security of that intermediate?

It can be precious going earlier and revisiting few of the components that affect the stability of carbocations.

And also, if you favor to look at it native the opposite next of the coin, right here are few of the determinants which do carbocations much more unstable.

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In our next post, we’ll describe the reasons for both ortho-, para- and meta- direction, and try to show why halogens to the right in the previous category however not the latter.