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29 Ιαν 2018 · Examples of ortho-, para – directors are hydroxyl groups, ethers, amines, alkyl groups, thiols, and halogens. Here’s a concrete example: the nitration of methoxybenzene (also known as anisole). ortho- and para- products dominate, while meta – products comprise less than 3%.
- Understanding Ortho, Para, and Meta Directors
We’ll look at a generic electrophilic aromatic substitution...
- Understanding Ortho, Para, and Meta Directors
2 Φεβ 2018 · We’ll look at a generic electrophilic aromatic substitution reaction of benzene with an ortho-, para- director (methoxybenzene) and examine the intermediates that are obtained from attack at the ortho, meta, and para positions.
The influence of meta-directing substituents can be explained using the same kinds of arguments used for ortho and para directors. Look at the nitration of benzaldehyde, for instance ( Figure 16.17 ).
As you saw in Section 16.4, a substituent on a benzene ring can be an activator or a deactivator. At the same time, a substituent can also be a meta director or an ortho/para director. Of the four possible combinations, only three are known—there are no meta directing activators.
9 Νοε 2017 · Substituents on benzene tend to fall into one of two categories: ortho–para directors, or meta directors. If you’re sharp, you might have already made an intuitive leap: the ortho- para- directing methyl group is an activating group, and the meta- directing nitro group is deactivating.
A substituent on the benzene ring also influences the orientation that the incoming EAS takes place (i.e., which position the incoming group occupies), this is the directing effect. There are two types of directors specifically: ortho-para directors and meta directors.
This is known as the ortho-para directing effect. The effect can be explained by drawing resonance contributors for the carbocation intermediate of the S E Ar reaction: the positive charge is in position to be delocalized by resonance only in reactions leading to ortho or para substitution.
